Pull percpureserve into release branch

[linux-2.6] / drivers / usb / gadget / file_storage.c

/*
 * file_storage.c -- File-backed USB Storage Gadget, for USB development
 *
 * Copyright (C) 2003-2007 Alan Stern
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions, and the following disclaimer,
 *    without modification.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The names of the above-listed copyright holders may not be used
 *    to endorse or promote products derived from this software without
 *    specific prior written permission.
 *
 * ALTERNATIVELY, this software may be distributed under the terms of the
 * GNU General Public License ("GPL") as published by the Free Software
 * Foundation, either version 2 of that License or (at your option) any
 * later version.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */


/*
 * The File-backed Storage Gadget acts as a USB Mass Storage device,
 * appearing to the host as a disk drive.  In addition to providing an
 * example of a genuinely useful gadget driver for a USB device, it also
 * illustrates a technique of double-buffering for increased throughput.
 * Last but not least, it gives an easy way to probe the behavior of the
 * Mass Storage drivers in a USB host.
 *
 * Backing storage is provided by a regular file or a block device, specified
 * by the "file" module parameter.  Access can be limited to read-only by
 * setting the optional "ro" module parameter.  The gadget will indicate that
 * it has removable media if the optional "removable" module parameter is set.
 *
 * The gadget supports the Control-Bulk (CB), Control-Bulk-Interrupt (CBI),
 * and Bulk-Only (also known as Bulk-Bulk-Bulk or BBB) transports, selected
 * by the optional "transport" module parameter.  It also supports the
 * following protocols: RBC (0x01), ATAPI or SFF-8020i (0x02), QIC-157 (0c03),
 * UFI (0x04), SFF-8070i (0x05), and transparent SCSI (0x06), selected by
 * the optional "protocol" module parameter.  In addition, the default
 * Vendor ID, Product ID, and release number can be overridden.
 *
 * There is support for multiple logical units (LUNs), each of which has
 * its own backing file.  The number of LUNs can be set using the optional
 * "luns" module parameter (anywhere from 1 to 8), and the corresponding
 * files are specified using comma-separated lists for "file" and "ro".
 * The default number of LUNs is taken from the number of "file" elements;
 * it is 1 if "file" is not given.  If "removable" is not set then a backing
 * file must be specified for each LUN.  If it is set, then an unspecified
 * or empty backing filename means the LUN's medium is not loaded.
 *
 * Requirements are modest; only a bulk-in and a bulk-out endpoint are
 * needed (an interrupt-out endpoint is also needed for CBI).  The memory
 * requirement amounts to two 16K buffers, size configurable by a parameter.
 * Support is included for both full-speed and high-speed operation.
 *
 * Note that the driver is slightly non-portable in that it assumes a
 * single memory/DMA buffer will be useable for bulk-in, bulk-out, and
 * interrupt-in endpoints.  With most device controllers this isn't an
 * issue, but there may be some with hardware restrictions that prevent
 * a buffer from being used by more than one endpoint.
 *
 * Module options:
 *
 *      file=filename[,filename...]
 *                              Required if "removable" is not set, names of
 *                                      the files or block devices used for
 *                                      backing storage
 *      ro=b[,b...]             Default false, booleans for read-only access
 *      removable               Default false, boolean for removable media
 *      luns=N                  Default N = number of filenames, number of
 *                                      LUNs to support
 *      stall                   Default determined according to the type of
 *                                      USB device controller (usually true),
 *                                      boolean to permit the driver to halt
 *                                      bulk endpoints
 *      transport=XXX           Default BBB, transport name (CB, CBI, or BBB)
 *      protocol=YYY            Default SCSI, protocol name (RBC, 8020 or
 *                                      ATAPI, QIC, UFI, 8070, or SCSI;
 *                                      also 1 - 6)
 *      vendor=0xVVVV           Default 0x0525 (NetChip), USB Vendor ID
 *      product=0xPPPP          Default 0xa4a5 (FSG), USB Product ID
 *      release=0xRRRR          Override the USB release number (bcdDevice)
 *      buflen=N                Default N=16384, buffer size used (will be
 *                                      rounded down to a multiple of
 *                                      PAGE_CACHE_SIZE)
 *
 * If CONFIG_USB_FILE_STORAGE_TEST is not set, only the "file", "ro",
 * "removable", "luns", and "stall" options are available; default values
 * are used for everything else.
 *
 * The pathnames of the backing files and the ro settings are available in
 * the attribute files "file" and "ro" in the lun<n> subdirectory of the
 * gadget's sysfs directory.  If the "removable" option is set, writing to
 * these files will simulate ejecting/loading the medium (writing an empty
 * line means eject) and adjusting a write-enable tab.  Changes to the ro
 * setting are not allowed when the medium is loaded.
 *
 * This gadget driver is heavily based on "Gadget Zero" by David Brownell.
 * The driver's SCSI command interface was based on the "Information
 * technology - Small Computer System Interface - 2" document from
 * X3T9.2 Project 375D, Revision 10L, 7-SEP-93, available at
 * <http://www.t10.org/ftp/t10/drafts/s2/s2-r10l.pdf>.  The single exception
 * is opcode 0x23 (READ FORMAT CAPACITIES), which was based on the
 * "Universal Serial Bus Mass Storage Class UFI Command Specification"
 * document, Revision 1.0, December 14, 1998, available at
 * <http://www.usb.org/developers/devclass_docs/usbmass-ufi10.pdf>.
 */


/*
 *                              Driver Design
 *
 * The FSG driver is fairly straightforward.  There is a main kernel
 * thread that handles most of the work.  Interrupt routines field
 * callbacks from the controller driver: bulk- and interrupt-request
 * completion notifications, endpoint-0 events, and disconnect events.
 * Completion events are passed to the main thread by wakeup calls.  Many
 * ep0 requests are handled at interrupt time, but SetInterface,
 * SetConfiguration, and device reset requests are forwarded to the
 * thread in the form of "exceptions" using SIGUSR1 signals (since they
 * should interrupt any ongoing file I/O operations).
 *
 * The thread's main routine implements the standard command/data/status
 * parts of a SCSI interaction.  It and its subroutines are full of tests
 * for pending signals/exceptions -- all this polling is necessary since
 * the kernel has no setjmp/longjmp equivalents.  (Maybe this is an
 * indication that the driver really wants to be running in userspace.)
 * An important point is that so long as the thread is alive it keeps an
 * open reference to the backing file.  This will prevent unmounting
 * the backing file's underlying filesystem and could cause problems
 * during system shutdown, for example.  To prevent such problems, the
 * thread catches INT, TERM, and KILL signals and converts them into
 * an EXIT exception.
 *
 * In normal operation the main thread is started during the gadget's
 * fsg_bind() callback and stopped during fsg_unbind().  But it can also
 * exit when it receives a signal, and there's no point leaving the
 * gadget running when the thread is dead.  So just before the thread
 * exits, it deregisters the gadget driver.  This makes things a little
 * tricky: The driver is deregistered at two places, and the exiting
 * thread can indirectly call fsg_unbind() which in turn can tell the
 * thread to exit.  The first problem is resolved through the use of the
 * REGISTERED atomic bitflag; the driver will only be deregistered once.
 * The second problem is resolved by having fsg_unbind() check
 * fsg->state; it won't try to stop the thread if the state is already
 * FSG_STATE_TERMINATED.
 *
 * To provide maximum throughput, the driver uses a circular pipeline of
 * buffer heads (struct fsg_buffhd).  In principle the pipeline can be
 * arbitrarily long; in practice the benefits don't justify having more
 * than 2 stages (i.e., double buffering).  But it helps to think of the
 * pipeline as being a long one.  Each buffer head contains a bulk-in and
 * a bulk-out request pointer (since the buffer can be used for both
 * output and input -- directions always are given from the host's
 * point of view) as well as a pointer to the buffer and various state
 * variables.
 *
 * Use of the pipeline follows a simple protocol.  There is a variable
 * (fsg->next_buffhd_to_fill) that points to the next buffer head to use.
 * At any time that buffer head may still be in use from an earlier
 * request, so each buffer head has a state variable indicating whether
 * it is EMPTY, FULL, or BUSY.  Typical use involves waiting for the
 * buffer head to be EMPTY, filling the buffer either by file I/O or by
 * USB I/O (during which the buffer head is BUSY), and marking the buffer
 * head FULL when the I/O is complete.  Then the buffer will be emptied
 * (again possibly by USB I/O, during which it is marked BUSY) and
 * finally marked EMPTY again (possibly by a completion routine).
 *
 * A module parameter tells the driver to avoid stalling the bulk
 * endpoints wherever the transport specification allows.  This is
 * necessary for some UDCs like the SuperH, which cannot reliably clear a
 * halt on a bulk endpoint.  However, under certain circumstances the
 * Bulk-only specification requires a stall.  In such cases the driver
 * will halt the endpoint and set a flag indicating that it should clear
 * the halt in software during the next device reset.  Hopefully this
 * will permit everything to work correctly.  Furthermore, although the
 * specification allows the bulk-out endpoint to halt when the host sends
 * too much data, implementing this would cause an unavoidable race.
 * The driver will always use the "no-stall" approach for OUT transfers.
 *
 * One subtle point concerns sending status-stage responses for ep0
 * requests.  Some of these requests, such as device reset, can involve
 * interrupting an ongoing file I/O operation, which might take an
 * arbitrarily long time.  During that delay the host might give up on
 * the original ep0 request and issue a new one.  When that happens the
 * driver should not notify the host about completion of the original
 * request, as the host will no longer be waiting for it.  So the driver
 * assigns to each ep0 request a unique tag, and it keeps track of the
 * tag value of the request associated with a long-running exception
 * (device-reset, interface-change, or configuration-change).  When the
 * exception handler is finished, the status-stage response is submitted
 * only if the current ep0 request tag is equal to the exception request
 * tag.  Thus only the most recently received ep0 request will get a
 * status-stage response.
 *
 * Warning: This driver source file is too long.  It ought to be split up
 * into a header file plus about 3 separate .c files, to handle the details
 * of the Gadget, USB Mass Storage, and SCSI protocols.
 */


/* #define VERBOSE_DEBUG */
/* #define DUMP_MSGS */


#include <linux/blkdev.h>
#include <linux/completion.h>
#include <linux/dcache.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/fcntl.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/kref.h>
#include <linux/kthread.h>
#include <linux/limits.h>
#include <linux/rwsem.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <linux/freezer.h>
#include <linux/utsname.h>

#include <linux/usb/ch9.h>
#include <linux/usb/gadget.h>

#include "gadget_chips.h"


/*-------------------------------------------------------------------------*/

#define DRIVER_DESC             "File-backed Storage Gadget"
#define DRIVER_NAME             "g_file_storage"
#define DRIVER_VERSION          "7 August 2007"

static const char longname[] = DRIVER_DESC;
static const char shortname[] = DRIVER_NAME;

MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_AUTHOR("Alan Stern");
MODULE_LICENSE("Dual BSD/GPL");

/* Thanks to NetChip Technologies for donating this product ID.
 *
 * DO NOT REUSE THESE IDs with any other driver!!  Ever!!
 * Instead:  allocate your own, using normal USB-IF procedures. */
#define DRIVER_VENDOR_ID        0x0525  // NetChip
#define DRIVER_PRODUCT_ID       0xa4a5  // Linux-USB File-backed Storage Gadget


/*
 * This driver assumes self-powered hardware and has no way for users to
 * trigger remote wakeup.  It uses autoconfiguration to select endpoints
 * and endpoint addresses.
 */


/*-------------------------------------------------------------------------*/

#define LDBG(lun,fmt,args...) \
        dev_dbg(&(lun)->dev , fmt , ## args)
#define MDBG(fmt,args...) \
        pr_debug(DRIVER_NAME ": " fmt , ## args)

#ifndef DEBUG
#undef VERBOSE_DEBUG
#undef DUMP_MSGS
#endif /* !DEBUG */

#ifdef VERBOSE_DEBUG
#define VLDBG   LDBG
#else
#define VLDBG(lun,fmt,args...) \
        do { } while (0)
#endif /* VERBOSE_DEBUG */

#define LERROR(lun,fmt,args...) \
        dev_err(&(lun)->dev , fmt , ## args)
#define LWARN(lun,fmt,args...) \
        dev_warn(&(lun)->dev , fmt , ## args)
#define LINFO(lun,fmt,args...) \
        dev_info(&(lun)->dev , fmt , ## args)

#define MINFO(fmt,args...) \
        pr_info(DRIVER_NAME ": " fmt , ## args)

#define DBG(d, fmt, args...) \
        dev_dbg(&(d)->gadget->dev , fmt , ## args)
#define VDBG(d, fmt, args...) \
        dev_vdbg(&(d)->gadget->dev , fmt , ## args)
#define ERROR(d, fmt, args...) \
        dev_err(&(d)->gadget->dev , fmt , ## args)
#define WARN(d, fmt, args...) \
        dev_warn(&(d)->gadget->dev , fmt , ## args)
#define INFO(d, fmt, args...) \
        dev_info(&(d)->gadget->dev , fmt , ## args)


/*-------------------------------------------------------------------------*/

/* Encapsulate the module parameter settings */

#define MAX_LUNS        8

static struct {
        char            *file[MAX_LUNS];
        int             ro[MAX_LUNS];
        unsigned int    num_filenames;
        unsigned int    num_ros;
        unsigned int    nluns;

        int             removable;
        int             can_stall;

        char            *transport_parm;
        char            *protocol_parm;
        unsigned short  vendor;
        unsigned short  product;
        unsigned short  release;
        unsigned int    buflen;

        int             transport_type;
        char            *transport_name;
        int             protocol_type;
        char            *protocol_name;

} mod_data = {                                  // Default values
        .transport_parm         = "BBB",
        .protocol_parm          = "SCSI",
        .removable              = 0,
        .can_stall              = 1,
        .vendor                 = DRIVER_VENDOR_ID,
        .product                = DRIVER_PRODUCT_ID,
        .release                = 0xffff,       // Use controller chip type
        .buflen                 = 16384,
        };


module_param_array_named(file, mod_data.file, charp, &mod_data.num_filenames,
                S_IRUGO);
MODULE_PARM_DESC(file, "names of backing files or devices");

module_param_array_named(ro, mod_data.ro, bool, &mod_data.num_ros, S_IRUGO);
MODULE_PARM_DESC(ro, "true to force read-only");

module_param_named(luns, mod_data.nluns, uint, S_IRUGO);
MODULE_PARM_DESC(luns, "number of LUNs");

module_param_named(removable, mod_data.removable, bool, S_IRUGO);
MODULE_PARM_DESC(removable, "true to simulate removable media");

module_param_named(stall, mod_data.can_stall, bool, S_IRUGO);
MODULE_PARM_DESC(stall, "false to prevent bulk stalls");


/* In the non-TEST version, only the module parameters listed above
 * are available. */
#ifdef CONFIG_USB_FILE_STORAGE_TEST

module_param_named(transport, mod_data.transport_parm, charp, S_IRUGO);
MODULE_PARM_DESC(transport, "type of transport (BBB, CBI, or CB)");

module_param_named(protocol, mod_data.protocol_parm, charp, S_IRUGO);
MODULE_PARM_DESC(protocol, "type of protocol (RBC, 8020, QIC, UFI, "
                "8070, or SCSI)");

module_param_named(vendor, mod_data.vendor, ushort, S_IRUGO);
MODULE_PARM_DESC(vendor, "USB Vendor ID");

module_param_named(product, mod_data.product, ushort, S_IRUGO);
MODULE_PARM_DESC(product, "USB Product ID");

module_param_named(release, mod_data.release, ushort, S_IRUGO);
MODULE_PARM_DESC(release, "USB release number");

module_param_named(buflen, mod_data.buflen, uint, S_IRUGO);
MODULE_PARM_DESC(buflen, "I/O buffer size");

#endif /* CONFIG_USB_FILE_STORAGE_TEST */


/*-------------------------------------------------------------------------*/

/* USB protocol value = the transport method */
#define USB_PR_CBI      0x00            // Control/Bulk/Interrupt
#define USB_PR_CB       0x01            // Control/Bulk w/o interrupt
#define USB_PR_BULK     0x50            // Bulk-only

/* USB subclass value = the protocol encapsulation */
#define USB_SC_RBC      0x01            // Reduced Block Commands (flash)
#define USB_SC_8020     0x02            // SFF-8020i, MMC-2, ATAPI (CD-ROM)
#define USB_SC_QIC      0x03            // QIC-157 (tape)
#define USB_SC_UFI      0x04            // UFI (floppy)
#define USB_SC_8070     0x05            // SFF-8070i (removable)
#define USB_SC_SCSI     0x06            // Transparent SCSI

/* Bulk-only data structures */

/* Command Block Wrapper */
struct bulk_cb_wrap {
        __le32  Signature;              // Contains 'USBC'
        u32     Tag;                    // Unique per command id
        __le32  DataTransferLength;     // Size of the data
        u8      Flags;                  // Direction in bit 7
        u8      Lun;                    // LUN (normally 0)
        u8      Length;                 // Of the CDB, <= MAX_COMMAND_SIZE
        u8      CDB[16];                // Command Data Block
};

#define USB_BULK_CB_WRAP_LEN    31
#define USB_BULK_CB_SIG         0x43425355      // Spells out USBC
#define USB_BULK_IN_FLAG        0x80

/* Command Status Wrapper */
struct bulk_cs_wrap {
        __le32  Signature;              // Should = 'USBS'
        u32     Tag;                    // Same as original command
        __le32  Residue;                // Amount not transferred
        u8      Status;                 // See below
};

#define USB_BULK_CS_WRAP_LEN    13
#define USB_BULK_CS_SIG         0x53425355      // Spells out 'USBS'
#define USB_STATUS_PASS         0
#define USB_STATUS_FAIL         1
#define USB_STATUS_PHASE_ERROR  2

/* Bulk-only class specific requests */
#define USB_BULK_RESET_REQUEST          0xff
#define USB_BULK_GET_MAX_LUN_REQUEST    0xfe


/* CBI Interrupt data structure */
struct interrupt_data {
        u8      bType;
        u8      bValue;
};

#define CBI_INTERRUPT_DATA_LEN          2

/* CBI Accept Device-Specific Command request */
#define USB_CBI_ADSC_REQUEST            0x00


#define MAX_COMMAND_SIZE        16      // Length of a SCSI Command Data Block

/* SCSI commands that we recognize */
#define SC_FORMAT_UNIT                  0x04
#define SC_INQUIRY                      0x12
#define SC_MODE_SELECT_6                0x15
#define SC_MODE_SELECT_10               0x55
#define SC_MODE_SENSE_6                 0x1a
#define SC_MODE_SENSE_10                0x5a
#define SC_PREVENT_ALLOW_MEDIUM_REMOVAL 0x1e
#define SC_READ_6                       0x08
#define SC_READ_10                      0x28
#define SC_READ_12                      0xa8
#define SC_READ_CAPACITY                0x25
#define SC_READ_FORMAT_CAPACITIES       0x23
#define SC_RELEASE                      0x17
#define SC_REQUEST_SENSE                0x03
#define SC_RESERVE                      0x16
#define SC_SEND_DIAGNOSTIC              0x1d
#define SC_START_STOP_UNIT              0x1b
#define SC_SYNCHRONIZE_CACHE            0x35
#define SC_TEST_UNIT_READY              0x00
#define SC_VERIFY                       0x2f
#define SC_WRITE_6                      0x0a
#define SC_WRITE_10                     0x2a
#define SC_WRITE_12                     0xaa

/* SCSI Sense Key/Additional Sense Code/ASC Qualifier values */
#define SS_NO_SENSE                             0
#define SS_COMMUNICATION_FAILURE                0x040800
#define SS_INVALID_COMMAND                      0x052000
#define SS_INVALID_FIELD_IN_CDB                 0x052400
#define SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE   0x052100
#define SS_LOGICAL_UNIT_NOT_SUPPORTED           0x052500
#define SS_MEDIUM_NOT_PRESENT                   0x023a00
#define SS_MEDIUM_REMOVAL_PREVENTED             0x055302
#define SS_NOT_READY_TO_READY_TRANSITION        0x062800
#define SS_RESET_OCCURRED                       0x062900
#define SS_SAVING_PARAMETERS_NOT_SUPPORTED      0x053900
#define SS_UNRECOVERED_READ_ERROR               0x031100
#define SS_WRITE_ERROR                          0x030c02
#define SS_WRITE_PROTECTED                      0x072700

#define SK(x)           ((u8) ((x) >> 16))      // Sense Key byte, etc.
#define ASC(x)          ((u8) ((x) >> 8))
#define ASCQ(x)         ((u8) (x))


/*-------------------------------------------------------------------------*/

/*
 * These definitions will permit the compiler to avoid generating code for
 * parts of the driver that aren't used in the non-TEST version.  Even gcc
 * can recognize when a test of a constant expression yields a dead code
 * path.
 */

#ifdef CONFIG_USB_FILE_STORAGE_TEST

#define transport_is_bbb()      (mod_data.transport_type == USB_PR_BULK)
#define transport_is_cbi()      (mod_data.transport_type == USB_PR_CBI)
#define protocol_is_scsi()      (mod_data.protocol_type == USB_SC_SCSI)

#else

#define transport_is_bbb()      1
#define transport_is_cbi()      0
#define protocol_is_scsi()      1

#endif /* CONFIG_USB_FILE_STORAGE_TEST */


struct lun {
        struct file     *filp;
        loff_t          file_length;
        loff_t          num_sectors;

        unsigned int    ro : 1;
        unsigned int    prevent_medium_removal : 1;
        unsigned int    registered : 1;
        unsigned int    info_valid : 1;

        u32             sense_data;
        u32             sense_data_info;
        u32             unit_attention_data;

        struct device   dev;
};

#define backing_file_is_open(curlun)    ((curlun)->filp != NULL)

static struct lun *dev_to_lun(struct device *dev)
{
        return container_of(dev, struct lun, dev);
}


/* Big enough to hold our biggest descriptor */
#define EP0_BUFSIZE     256
#define DELAYED_STATUS  (EP0_BUFSIZE + 999)     // An impossibly large value

/* Number of buffers we will use.  2 is enough for double-buffering */
#define NUM_BUFFERS     2

enum fsg_buffer_state {
        BUF_STATE_EMPTY = 0,
        BUF_STATE_FULL,
        BUF_STATE_BUSY
};

struct fsg_buffhd {
        void                            *buf;
        enum fsg_buffer_state           state;
        struct fsg_buffhd               *next;

        /* The NetChip 2280 is faster, and handles some protocol faults
         * better, if we don't submit any short bulk-out read requests.
         * So we will record the intended request length here. */
        unsigned int                    bulk_out_intended_length;

        struct usb_request              *inreq;
        int                             inreq_busy;
        struct usb_request              *outreq;
        int                             outreq_busy;
};

enum fsg_state {
        FSG_STATE_COMMAND_PHASE = -10,          // This one isn't used anywhere
        FSG_STATE_DATA_PHASE,
        FSG_STATE_STATUS_PHASE,

        FSG_STATE_IDLE = 0,
        FSG_STATE_ABORT_BULK_OUT,
        FSG_STATE_RESET,
        FSG_STATE_INTERFACE_CHANGE,
        FSG_STATE_CONFIG_CHANGE,
        FSG_STATE_DISCONNECT,
        FSG_STATE_EXIT,
        FSG_STATE_TERMINATED
};

enum data_direction {
        DATA_DIR_UNKNOWN = 0,
        DATA_DIR_FROM_HOST,
        DATA_DIR_TO_HOST,
        DATA_DIR_NONE
};

struct fsg_dev {
        /* lock protects: state, all the req_busy's, and cbbuf_cmnd */
        spinlock_t              lock;
        struct usb_gadget       *gadget;

        /* filesem protects: backing files in use */
        struct rw_semaphore     filesem;

        /* reference counting: wait until all LUNs are released */
        struct kref             ref;

        struct usb_ep           *ep0;           // Handy copy of gadget->ep0
        struct usb_request      *ep0req;        // For control responses
        unsigned int            ep0_req_tag;
        const char              *ep0req_name;

        struct usb_request      *intreq;        // For interrupt responses
        int                     intreq_busy;
        struct fsg_buffhd       *intr_buffhd;

        unsigned int            bulk_out_maxpacket;
        enum fsg_state          state;          // For exception handling
        unsigned int            exception_req_tag;

        u8                      config, new_config;

        unsigned int            running : 1;
        unsigned int            bulk_in_enabled : 1;
        unsigned int            bulk_out_enabled : 1;
        unsigned int            intr_in_enabled : 1;
        unsigned int            phase_error : 1;
        unsigned int            short_packet_received : 1;
        unsigned int            bad_lun_okay : 1;

        unsigned long           atomic_bitflags;
#define REGISTERED              0
#define CLEAR_BULK_HALTS        1
#define SUSPENDED               2

        struct usb_ep           *bulk_in;
        struct usb_ep           *bulk_out;
        struct usb_ep           *intr_in;

        struct fsg_buffhd       *next_buffhd_to_fill;
        struct fsg_buffhd       *next_buffhd_to_drain;
        struct fsg_buffhd       buffhds[NUM_BUFFERS];

        int                     thread_wakeup_needed;
        struct completion       thread_notifier;
        struct task_struct      *thread_task;

        int                     cmnd_size;
        u8                      cmnd[MAX_COMMAND_SIZE];
        enum data_direction     data_dir;
        u32                     data_size;
        u32                     data_size_from_cmnd;
        u32                     tag;
        unsigned int            lun;
        u32                     residue;
        u32                     usb_amount_left;

        /* The CB protocol offers no way for a host to know when a command
         * has completed.  As a result the next command may arrive early,
         * and we will still have to handle it.  For that reason we need
         * a buffer to store new commands when using CB (or CBI, which
         * does not oblige a host to wait for command completion either). */
        int                     cbbuf_cmnd_size;
        u8                      cbbuf_cmnd[MAX_COMMAND_SIZE];

        unsigned int            nluns;
        struct lun              *luns;
        struct lun              *curlun;
};

typedef void (*fsg_routine_t)(struct fsg_dev *);

static int exception_in_progress(struct fsg_dev *fsg)
{
        return (fsg->state > FSG_STATE_IDLE);
}

/* Make bulk-out requests be divisible by the maxpacket size */
static void set_bulk_out_req_length(struct fsg_dev *fsg,
                struct fsg_buffhd *bh, unsigned int length)
{
        unsigned int    rem;

        bh->bulk_out_intended_length = length;
        rem = length % fsg->bulk_out_maxpacket;
        if (rem > 0)
                length += fsg->bulk_out_maxpacket - rem;
        bh->outreq->length = length;
}

static struct fsg_dev                   *the_fsg;
static struct usb_gadget_driver         fsg_driver;

static void     close_backing_file(struct lun *curlun);
static void     close_all_backing_files(struct fsg_dev *fsg);


/*-------------------------------------------------------------------------*/

#ifdef DUMP_MSGS

static void dump_msg(struct fsg_dev *fsg, const char *label,
                const u8 *buf, unsigned int length)
{
        if (length < 512) {
                DBG(fsg, "%s, length %u:\n", label, length);
                print_hex_dump(KERN_DEBUG, "", DUMP_PREFIX_OFFSET,
                                16, 1, buf, length, 0);
        }
}

static void dump_cdb(struct fsg_dev *fsg)
{}

#else

static void dump_msg(struct fsg_dev *fsg, const char *label,
                const u8 *buf, unsigned int length)
{}

#ifdef VERBOSE_DEBUG

static void dump_cdb(struct fsg_dev *fsg)
{
        print_hex_dump(KERN_DEBUG, "SCSI CDB: ", DUMP_PREFIX_NONE,
                        16, 1, fsg->cmnd, fsg->cmnd_size, 0);
}

#else

static void dump_cdb(struct fsg_dev *fsg)
{}

#endif /* VERBOSE_DEBUG */
#endif /* DUMP_MSGS */


static int fsg_set_halt(struct fsg_dev *fsg, struct usb_ep *ep)
{
        const char      *name;

        if (ep == fsg->bulk_in)
                name = "bulk-in";
        else if (ep == fsg->bulk_out)
                name = "bulk-out";
        else
                name = ep->name;
        DBG(fsg, "%s set halt\n", name);
        return usb_ep_set_halt(ep);
}


/*-------------------------------------------------------------------------*/

/* Routines for unaligned data access */

static u16 get_be16(u8 *buf)
{
        return ((u16) buf[0] << 8) | ((u16) buf[1]);
}

static u32 get_be32(u8 *buf)
{
        return ((u32) buf[0] << 24) | ((u32) buf[1] << 16) |
                        ((u32) buf[2] << 8) | ((u32) buf[3]);
}

static void put_be16(u8 *buf, u16 val)
{
        buf[0] = val >> 8;
        buf[1] = val;
}

static void put_be32(u8 *buf, u32 val)
{
        buf[0] = val >> 24;
        buf[1] = val >> 16;
        buf[2] = val >> 8;
        buf[3] = val & 0xff;
}


/*-------------------------------------------------------------------------*/

/*
 * DESCRIPTORS ... most are static, but strings and (full) configuration
 * descriptors are built on demand.  Also the (static) config and interface
 * descriptors are adjusted during fsg_bind().
 */
#define STRING_MANUFACTURER     1
#define STRING_PRODUCT          2
#define STRING_SERIAL           3
#define STRING_CONFIG           4
#define STRING_INTERFACE        5

/* There is only one configuration. */
#define CONFIG_VALUE            1

static struct usb_device_descriptor
device_desc = {
        .bLength =              sizeof device_desc,
        .bDescriptorType =      USB_DT_DEVICE,

        .bcdUSB =               __constant_cpu_to_le16(0x0200),
        .bDeviceClass =         USB_CLASS_PER_INTERFACE,

        /* The next three values can be overridden by module parameters */
        .idVendor =             __constant_cpu_to_le16(DRIVER_VENDOR_ID),
        .idProduct =            __constant_cpu_to_le16(DRIVER_PRODUCT_ID),
        .bcdDevice =            __constant_cpu_to_le16(0xffff),

        .iManufacturer =        STRING_MANUFACTURER,
        .iProduct =             STRING_PRODUCT,
        .iSerialNumber =        STRING_SERIAL,
        .bNumConfigurations =   1,
};

static struct usb_config_descriptor
config_desc = {
        .bLength =              sizeof config_desc,
        .bDescriptorType =      USB_DT_CONFIG,

        /* wTotalLength computed by usb_gadget_config_buf() */
        .bNumInterfaces =       1,
        .bConfigurationValue =  CONFIG_VALUE,
        .iConfiguration =       STRING_CONFIG,
        .bmAttributes =         USB_CONFIG_ATT_ONE | USB_CONFIG_ATT_SELFPOWER,
        .bMaxPower =            1,      // self-powered
};

static struct usb_otg_descriptor
otg_desc = {
        .bLength =              sizeof(otg_desc),
        .bDescriptorType =      USB_DT_OTG,

        .bmAttributes =         USB_OTG_SRP,
};

/* There is only one interface. */

static struct usb_interface_descriptor
intf_desc = {
        .bLength =              sizeof intf_desc,
        .bDescriptorType =      USB_DT_INTERFACE,

        .bNumEndpoints =        2,              // Adjusted during fsg_bind()
        .bInterfaceClass =      USB_CLASS_MASS_STORAGE,
        .bInterfaceSubClass =   USB_SC_SCSI,    // Adjusted during fsg_bind()
        .bInterfaceProtocol =   USB_PR_BULK,    // Adjusted during fsg_bind()
        .iInterface =           STRING_INTERFACE,
};

/* Three full-speed endpoint descriptors: bulk-in, bulk-out,
 * and interrupt-in. */

static struct usb_endpoint_descriptor
fs_bulk_in_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,

        .bEndpointAddress =     USB_DIR_IN,
        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
        /* wMaxPacketSize set by autoconfiguration */
};

static struct usb_endpoint_descriptor
fs_bulk_out_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,

        .bEndpointAddress =     USB_DIR_OUT,
        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
        /* wMaxPacketSize set by autoconfiguration */
};

static struct usb_endpoint_descriptor
fs_intr_in_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,

        .bEndpointAddress =     USB_DIR_IN,
        .bmAttributes =         USB_ENDPOINT_XFER_INT,
        .wMaxPacketSize =       __constant_cpu_to_le16(2),
        .bInterval =            32,     // frames -> 32 ms
};

static const struct usb_descriptor_header *fs_function[] = {
        (struct usb_descriptor_header *) &otg_desc,
        (struct usb_descriptor_header *) &intf_desc,
        (struct usb_descriptor_header *) &fs_bulk_in_desc,
        (struct usb_descriptor_header *) &fs_bulk_out_desc,
        (struct usb_descriptor_header *) &fs_intr_in_desc,
        NULL,
};
#define FS_FUNCTION_PRE_EP_ENTRIES      2


/*
 * USB 2.0 devices need to expose both high speed and full speed
 * descriptors, unless they only run at full speed.
 *
 * That means alternate endpoint descriptors (bigger packets)
 * and a "device qualifier" ... plus more construction options
 * for the config descriptor.
 */
static struct usb_qualifier_descriptor
dev_qualifier = {
        .bLength =              sizeof dev_qualifier,
        .bDescriptorType =      USB_DT_DEVICE_QUALIFIER,

        .bcdUSB =               __constant_cpu_to_le16(0x0200),
        .bDeviceClass =         USB_CLASS_PER_INTERFACE,

        .bNumConfigurations =   1,
};

static struct usb_endpoint_descriptor
hs_bulk_in_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,

        /* bEndpointAddress copied from fs_bulk_in_desc during fsg_bind() */
        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
        .wMaxPacketSize =       __constant_cpu_to_le16(512),
};

static struct usb_endpoint_descriptor
hs_bulk_out_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,

        /* bEndpointAddress copied from fs_bulk_out_desc during fsg_bind() */
        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
        .wMaxPacketSize =       __constant_cpu_to_le16(512),
        .bInterval =            1,      // NAK every 1 uframe
};

static struct usb_endpoint_descriptor
hs_intr_in_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,

        /* bEndpointAddress copied from fs_intr_in_desc during fsg_bind() */
        .bmAttributes =         USB_ENDPOINT_XFER_INT,
        .wMaxPacketSize =       __constant_cpu_to_le16(2),
        .bInterval =            9,      // 2**(9-1) = 256 uframes -> 32 ms
};

static const struct usb_descriptor_header *hs_function[] = {
        (struct usb_descriptor_header *) &otg_desc,
        (struct usb_descriptor_header *) &intf_desc,
        (struct usb_descriptor_header *) &hs_bulk_in_desc,
        (struct usb_descriptor_header *) &hs_bulk_out_desc,
        (struct usb_descriptor_header *) &hs_intr_in_desc,
        NULL,
};
#define HS_FUNCTION_PRE_EP_ENTRIES      2

/* Maxpacket and other transfer characteristics vary by speed. */
static struct usb_endpoint_descriptor *
ep_desc(struct usb_gadget *g, struct usb_endpoint_descriptor *fs,
                struct usb_endpoint_descriptor *hs)
{
        if (gadget_is_dualspeed(g) && g->speed == USB_SPEED_HIGH)
                return hs;
        return fs;
}


/* The CBI specification limits the serial string to 12 uppercase hexadecimal
 * characters. */
static char                             manufacturer[64];
static char                             serial[13];

/* Static strings, in UTF-8 (for simplicity we use only ASCII characters) */
static struct usb_string                strings[] = {
        {STRING_MANUFACTURER,   manufacturer},
        {STRING_PRODUCT,        longname},
        {STRING_SERIAL,         serial},
        {STRING_CONFIG,         "Self-powered"},
        {STRING_INTERFACE,      "Mass Storage"},
        {}
};

static struct usb_gadget_strings        stringtab = {
        .language       = 0x0409,               // en-us
        .strings        = strings,
};


/*
 * Config descriptors must agree with the code that sets configurations
 * and with code managing interfaces and their altsettings.  They must
 * also handle different speeds and other-speed requests.
 */
static int populate_config_buf(struct usb_gadget *gadget,
                u8 *buf, u8 type, unsigned index)
{
        enum usb_device_speed                   speed = gadget->speed;
        int                                     len;
        const struct usb_descriptor_header      **function;

        if (index > 0)
                return -EINVAL;

        if (gadget_is_dualspeed(gadget) && type == USB_DT_OTHER_SPEED_CONFIG)
                speed = (USB_SPEED_FULL + USB_SPEED_HIGH) - speed;
        if (gadget_is_dualspeed(gadget) && speed == USB_SPEED_HIGH)
                function = hs_function;
        else
                function = fs_function;

        /* for now, don't advertise srp-only devices */
        if (!gadget_is_otg(gadget))
                function++;

        len = usb_gadget_config_buf(&config_desc, buf, EP0_BUFSIZE, function);
        ((struct usb_config_descriptor *) buf)->bDescriptorType = type;
        return len;
}


/*-------------------------------------------------------------------------*/

/* These routines may be called in process context or in_irq */

/* Caller must hold fsg->lock */
static void wakeup_thread(struct fsg_dev *fsg)
{
        /* Tell the main thread that something has happened */
        fsg->thread_wakeup_needed = 1;
        if (fsg->thread_task)
                wake_up_process(fsg->thread_task);
}


static void raise_exception(struct fsg_dev *fsg, enum fsg_state new_state)
{
        unsigned long           flags;

        /* Do nothing if a higher-priority exception is already in progress.
         * If a lower-or-equal priority exception is in progress, preempt it
         * and notify the main thread by sending it a signal. */
        spin_lock_irqsave(&fsg->lock, flags);
        if (fsg->state <= new_state) {
                fsg->exception_req_tag = fsg->ep0_req_tag;
                fsg->state = new_state;
                if (fsg->thread_task)
                        send_sig_info(SIGUSR1, SEND_SIG_FORCED,
                                        fsg->thread_task);
        }
        spin_unlock_irqrestore(&fsg->lock, flags);
}


/*-------------------------------------------------------------------------*/

/* The disconnect callback and ep0 routines.  These always run in_irq,
 * except that ep0_queue() is called in the main thread to acknowledge
 * completion of various requests: set config, set interface, and
 * Bulk-only device reset. */

static void fsg_disconnect(struct usb_gadget *gadget)
{
        struct fsg_dev          *fsg = get_gadget_data(gadget);

        DBG(fsg, "disconnect or port reset\n");
        raise_exception(fsg, FSG_STATE_DISCONNECT);
}


static int ep0_queue(struct fsg_dev *fsg)
{
        int     rc;

        rc = usb_ep_queue(fsg->ep0, fsg->ep0req, GFP_ATOMIC);
        if (rc != 0 && rc != -ESHUTDOWN) {

                /* We can't do much more than wait for a reset */
                WARN(fsg, "error in submission: %s --> %d\n",
                                fsg->ep0->name, rc);
        }
        return rc;
}

static void ep0_complete(struct usb_ep *ep, struct usb_request *req)
{
        struct fsg_dev          *fsg = ep->driver_data;

        if (req->actual > 0)
                dump_msg(fsg, fsg->ep0req_name, req->buf, req->actual);
        if (req->status || req->actual != req->length)
                DBG(fsg, "%s --> %d, %u/%u\n", __FUNCTION__,
                                req->status, req->actual, req->length);
        if (req->status == -ECONNRESET)         // Request was cancelled
                usb_ep_fifo_flush(ep);

        if (req->status == 0 && req->context)
                ((fsg_routine_t) (req->context))(fsg);
}


/*-------------------------------------------------------------------------*/

/* Bulk and interrupt endpoint completion handlers.
 * These always run in_irq. */

static void bulk_in_complete(struct usb_ep *ep, struct usb_request *req)
{
        struct fsg_dev          *fsg = ep->driver_data;
        struct fsg_buffhd       *bh = req->context;

        if (req->status || req->actual != req->length)
                DBG(fsg, "%s --> %d, %u/%u\n", __FUNCTION__,
                                req->status, req->actual, req->length);
        if (req->status == -ECONNRESET)         // Request was cancelled
                usb_ep_fifo_flush(ep);

        /* Hold the lock while we update the request and buffer states */
        smp_wmb();
        spin_lock(&fsg->lock);
        bh->inreq_busy = 0;
        bh->state = BUF_STATE_EMPTY;
        wakeup_thread(fsg);
        spin_unlock(&fsg->lock);
}

static void bulk_out_complete(struct usb_ep *ep, struct usb_request *req)
{
        struct fsg_dev          *fsg = ep->driver_data;
        struct fsg_buffhd       *bh = req->context;

        dump_msg(fsg, "bulk-out", req->buf, req->actual);
        if (req->status || req->actual != bh->bulk_out_intended_length)
                DBG(fsg, "%s --> %d, %u/%u\n", __FUNCTION__,
                                req->status, req->actual,
                                bh->bulk_out_intended_length);
        if (req->status == -ECONNRESET)         // Request was cancelled
                usb_ep_fifo_flush(ep);

        /* Hold the lock while we update the request and buffer states */
        smp_wmb();
        spin_lock(&fsg->lock);
        bh->outreq_busy = 0;
        bh->state = BUF_STATE_FULL;
        wakeup_thread(fsg);
        spin_unlock(&fsg->lock);
}


#ifdef CONFIG_USB_FILE_STORAGE_TEST
static void intr_in_complete(struct usb_ep *ep, struct usb_request *req)
{
        struct fsg_dev          *fsg = ep->driver_data;
        struct fsg_buffhd       *bh = req->context;

        if (req->status || req->actual != req->length)
                DBG(fsg, "%s --> %d, %u/%u\n", __FUNCTION__,
                                req->status, req->actual, req->length);
        if (req->status == -ECONNRESET)         // Request was cancelled
                usb_ep_fifo_flush(ep);

        /* Hold the lock while we update the request and buffer states */
        smp_wmb();
        spin_lock(&fsg->lock);
        fsg->intreq_busy = 0;
        bh->state = BUF_STATE_EMPTY;
        wakeup_thread(fsg);
        spin_unlock(&fsg->lock);
}

#else
static void intr_in_complete(struct usb_ep *ep, struct usb_request *req)
{}
#endif /* CONFIG_USB_FILE_STORAGE_TEST */


/*-------------------------------------------------------------------------*/

/* Ep0 class-specific handlers.  These always run in_irq. */

#ifdef CONFIG_USB_FILE_STORAGE_TEST
static void received_cbi_adsc(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{
        struct usb_request      *req = fsg->ep0req;
        static u8               cbi_reset_cmnd[6] = {
                        SC_SEND_DIAGNOSTIC, 4, 0xff, 0xff, 0xff, 0xff};

        /* Error in command transfer? */
        if (req->status || req->length != req->actual ||
                        req->actual < 6 || req->actual > MAX_COMMAND_SIZE) {

                /* Not all controllers allow a protocol stall after
                 * receiving control-out data, but we'll try anyway. */
                fsg_set_halt(fsg, fsg->ep0);
                return;                 // Wait for reset
        }

        /* Is it the special reset command? */
        if (req->actual >= sizeof cbi_reset_cmnd &&
                        memcmp(req->buf, cbi_reset_cmnd,
                                sizeof cbi_reset_cmnd) == 0) {

                /* Raise an exception to stop the current operation
                 * and reinitialize our state. */
                DBG(fsg, "cbi reset request\n");
                raise_exception(fsg, FSG_STATE_RESET);
                return;
        }

        VDBG(fsg, "CB[I] accept device-specific command\n");
        spin_lock(&fsg->lock);

        /* Save the command for later */
        if (fsg->cbbuf_cmnd_size)
                WARN(fsg, "CB[I] overwriting previous command\n");
        fsg->cbbuf_cmnd_size = req->actual;
        memcpy(fsg->cbbuf_cmnd, req->buf, fsg->cbbuf_cmnd_size);

        wakeup_thread(fsg);
        spin_unlock(&fsg->lock);
}

#else
static void received_cbi_adsc(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{}
#endif /* CONFIG_USB_FILE_STORAGE_TEST */


static int class_setup_req(struct fsg_dev *fsg,
                const struct usb_ctrlrequest *ctrl)
{
        struct usb_request      *req = fsg->ep0req;
        int                     value = -EOPNOTSUPP;
        u16                     w_index = le16_to_cpu(ctrl->wIndex);
        u16                     w_value = le16_to_cpu(ctrl->wValue);
        u16                     w_length = le16_to_cpu(ctrl->wLength);

        if (!fsg->config)
                return value;

        /* Handle Bulk-only class-specific requests */
        if (transport_is_bbb()) {
                switch (ctrl->bRequest) {

                case USB_BULK_RESET_REQUEST:
                        if (ctrl->bRequestType != (USB_DIR_OUT |
                                        USB_TYPE_CLASS | USB_RECIP_INTERFACE))
                                break;
                        if (w_index != 0 || w_value != 0) {
                                value = -EDOM;
                                break;
                        }

                        /* Raise an exception to stop the current operation
                         * and reinitialize our state. */
                        DBG(fsg, "bulk reset request\n");
                        raise_exception(fsg, FSG_STATE_RESET);
                        value = DELAYED_STATUS;
                        break;

                case USB_BULK_GET_MAX_LUN_REQUEST:
                        if (ctrl->bRequestType != (USB_DIR_IN |
                                        USB_TYPE_CLASS | USB_RECIP_INTERFACE))
                                break;
                        if (w_index != 0 || w_value != 0) {
                                value = -EDOM;
                                break;
                        }
                        VDBG(fsg, "get max LUN\n");
                        *(u8 *) req->buf = fsg->nluns - 1;
                        value = 1;
                        break;
                }
        }

        /* Handle CBI class-specific requests */
        else {
                switch (ctrl->bRequest) {

                case USB_CBI_ADSC_REQUEST:
                        if (ctrl->bRequestType != (USB_DIR_OUT |
                                        USB_TYPE_CLASS | USB_RECIP_INTERFACE))
                                break;
                        if (w_index != 0 || w_value != 0) {
                                value = -EDOM;
                                break;
                        }
                        if (w_length > MAX_COMMAND_SIZE) {
                                value = -EOVERFLOW;
                                break;
                        }
                        value = w_length;
                        fsg->ep0req->context = received_cbi_adsc;
                        break;
                }
        }

        if (value == -EOPNOTSUPP)
                VDBG(fsg,
                        "unknown class-specific control req "
                        "%02x.%02x v%04x i%04x l%u\n",
                        ctrl->bRequestType, ctrl->bRequest,
                        le16_to_cpu(ctrl->wValue), w_index, w_length);
        return value;
}


/*-------------------------------------------------------------------------*/

/* Ep0 standard request handlers.  These always run in_irq. */

static int standard_setup_req(struct fsg_dev *fsg,
                const struct usb_ctrlrequest *ctrl)
{
        struct usb_request      *req = fsg->ep0req;
        int                     value = -EOPNOTSUPP;
        u16                     w_index = le16_to_cpu(ctrl->wIndex);
        u16                     w_value = le16_to_cpu(ctrl->wValue);

        /* Usually this just stores reply data in the pre-allocated ep0 buffer,
         * but config change events will also reconfigure hardware. */
        switch (ctrl->bRequest) {

        case USB_REQ_GET_DESCRIPTOR:
                if (ctrl->bRequestType != (USB_DIR_IN | USB_TYPE_STANDARD |
                                USB_RECIP_DEVICE))
                        break;
                switch (w_value >> 8) {

                case USB_DT_DEVICE:
                        VDBG(fsg, "get device descriptor\n");
                        value = sizeof device_desc;
                        memcpy(req->buf, &device_desc, value);
                        break;
                case USB_DT_DEVICE_QUALIFIER:
                        VDBG(fsg, "get device qualifier\n");
                        if (!gadget_is_dualspeed(fsg->gadget))
                                break;
                        value = sizeof dev_qualifier;
                        memcpy(req->buf, &dev_qualifier, value);
                        break;

                case USB_DT_OTHER_SPEED_CONFIG:
                        VDBG(fsg, "get other-speed config descriptor\n");
                        if (!gadget_is_dualspeed(fsg->gadget))
                                break;
                        goto get_config;
                case USB_DT_CONFIG:
                        VDBG(fsg, "get configuration descriptor\n");
get_config:
                        value = populate_config_buf(fsg->gadget,
                                        req->buf,
                                        w_value >> 8,
                                        w_value & 0xff);
                        break;

                case USB_DT_STRING:
                        VDBG(fsg, "get string descriptor\n");

                        /* wIndex == language code */
                        value = usb_gadget_get_string(&stringtab,
                                        w_value & 0xff, req->buf);
                        break;
                }
                break;

        /* One config, two speeds */
        case USB_REQ_SET_CONFIGURATION:
                if (ctrl->bRequestType != (USB_DIR_OUT | USB_TYPE_STANDARD |
                                USB_RECIP_DEVICE))
                        break;
                VDBG(fsg, "set configuration\n");
                if (w_value == CONFIG_VALUE || w_value == 0) {
                        fsg->new_config = w_value;

                        /* Raise an exception to wipe out previous transaction
                         * state (queued bufs, etc) and set the new config. */
                        raise_exception(fsg, FSG_STATE_CONFIG_CHANGE);
                        value = DELAYED_STATUS;
                }
                break;
        case USB_REQ_GET_CONFIGURATION:
                if (ctrl->bRequestType != (USB_DIR_IN | USB_TYPE_STANDARD |
                                USB_RECIP_DEVICE))
                        break;
                VDBG(fsg, "get configuration\n");
                *(u8 *) req->buf = fsg->config;
                value = 1;
                break;

        case USB_REQ_SET_INTERFACE:
                if (ctrl->bRequestType != (USB_DIR_OUT| USB_TYPE_STANDARD |
                                USB_RECIP_INTERFACE))
                        break;
                if (fsg->config && w_index == 0) {

                        /* Raise an exception to wipe out previous transaction
                         * state (queued bufs, etc) and install the new
                         * interface altsetting. */
                        raise_exception(fsg, FSG_STATE_INTERFACE_CHANGE);
                        value = DELAYED_STATUS;
                }
                break;
        case USB_REQ_GET_INTERFACE:
                if (ctrl->bRequestType != (USB_DIR_IN | USB_TYPE_STANDARD |
                                USB_RECIP_INTERFACE))
                        break;
                if (!fsg->config)
                        break;
                if (w_index != 0) {
                        value = -EDOM;
                        break;
                }
                VDBG(fsg, "get interface\n");
                *(u8 *) req->buf = 0;
                value = 1;
                break;

        default:
                VDBG(fsg,
                        "unknown control req %02x.%02x v%04x i%04x l%u\n",
                        ctrl->bRequestType, ctrl->bRequest,
                        w_value, w_index, le16_to_cpu(ctrl->wLength));
        }

        return value;
}


static int fsg_setup(struct usb_gadget *gadget,
                const struct usb_ctrlrequest *ctrl)
{
        struct fsg_dev          *fsg = get_gadget_data(gadget);
        int                     rc;
        int                     w_length = le16_to_cpu(ctrl->wLength);

        ++fsg->ep0_req_tag;             // Record arrival of a new request
        fsg->ep0req->context = NULL;
        fsg->ep0req->length = 0;
        dump_msg(fsg, "ep0-setup", (u8 *) ctrl, sizeof(*ctrl));

        if ((ctrl->bRequestType & USB_TYPE_MASK) == USB_TYPE_CLASS)
                rc = class_setup_req(fsg, ctrl);
        else
                rc = standard_setup_req(fsg, ctrl);

        /* Respond with data/status or defer until later? */
        if (rc >= 0 && rc != DELAYED_STATUS) {
                rc = min(rc, w_length);
                fsg->ep0req->length = rc;
                fsg->ep0req->zero = rc < w_length;
                fsg->ep0req_name = (ctrl->bRequestType & USB_DIR_IN ?
                                "ep0-in" : "ep0-out");
                rc = ep0_queue(fsg);
        }

        /* Device either stalls (rc < 0) or reports success */
        return rc;
}


/*-------------------------------------------------------------------------*/

/* All the following routines run in process context */


/* Use this for bulk or interrupt transfers, not ep0 */
static void start_transfer(struct fsg_dev *fsg, struct usb_ep *ep,
                struct usb_request *req, int *pbusy,
                enum fsg_buffer_state *state)
{
        int     rc;

        if (ep == fsg->bulk_in)
                dump_msg(fsg, "bulk-in", req->buf, req->length);
        else if (ep == fsg->intr_in)
                dump_msg(fsg, "intr-in", req->buf, req->length);

        spin_lock_irq(&fsg->lock);
        *pbusy = 1;
        *state = BUF_STATE_BUSY;
        spin_unlock_irq(&fsg->lock);
        rc = usb_ep_queue(ep, req, GFP_KERNEL);
        if (rc != 0) {
                *pbusy = 0;
                *state = BUF_STATE_EMPTY;

                /* We can't do much more than wait for a reset */

                /* Note: currently the net2280 driver fails zero-length
                 * submissions if DMA is enabled. */
                if (rc != -ESHUTDOWN && !(rc == -EOPNOTSUPP &&
                                                req->length == 0))
                        WARN(fsg, "error in submission: %s --> %d\n",
                                        ep->name, rc);
        }
}


static int sleep_thread(struct fsg_dev *fsg)
{
        int     rc = 0;

        /* Wait until a signal arrives or we are woken up */
        for (;;) {
                try_to_freeze();
                set_current_state(TASK_INTERRUPTIBLE);
                if (signal_pending(current)) {
                        rc = -EINTR;
                        break;
                }
                if (fsg->thread_wakeup_needed)
                        break;
                schedule();
        }
        __set_current_state(TASK_RUNNING);
        fsg->thread_wakeup_needed = 0;
        return rc;
}


/*-------------------------------------------------------------------------*/

static int do_read(struct fsg_dev *fsg)
{
        struct lun              *curlun = fsg->curlun;
        u32                     lba;
        struct fsg_buffhd       *bh;
        int                     rc;
        u32                     amount_left;
        loff_t                  file_offset, file_offset_tmp;
        unsigned int            amount;
        unsigned int            partial_page;
        ssize_t                 nread;

        /* Get the starting Logical Block Address and check that it's
         * not too big */
        if (fsg->cmnd[0] == SC_READ_6)
                lba = (fsg->cmnd[1] << 16) | get_be16(&fsg->cmnd[2]);
        else {
                lba = get_be32(&fsg->cmnd[2]);

                /* We allow DPO (Disable Page Out = don't save data in the
                 * cache) and FUA (Force Unit Access = don't read from the
                 * cache), but we don't implement them. */
                if ((fsg->cmnd[1] & ~0x18) != 0) {
                        curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                        return -EINVAL;
                }
        }
        if (lba >= curlun->num_sectors) {
                curlun->sense_data = SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
                return -EINVAL;
        }
        file_offset = ((loff_t) lba) << 9;

        /* Carry out the file reads */
        amount_left = fsg->data_size_from_cmnd;
        if (unlikely(amount_left == 0))
                return -EIO;            // No default reply

        for (;;) {

                /* Figure out how much we need to read:
                 * Try to read the remaining amount.
                 * But don't read more than the buffer size.
                 * And don't try to read past the end of the file.
                 * Finally, if we're not at a page boundary, don't read past
                 *      the next page.
                 * If this means reading 0 then we were asked to read past
                 *      the end of file. */
                amount = min((unsigned int) amount_left, mod_data.buflen);
                amount = min((loff_t) amount,
                                curlun->file_length - file_offset);
                partial_page = file_offset & (PAGE_CACHE_SIZE - 1);
                if (partial_page > 0)
                        amount = min(amount, (unsigned int) PAGE_CACHE_SIZE -
                                        partial_page);

                /* Wait for the next buffer to become available */
                bh = fsg->next_buffhd_to_fill;
                while (bh->state != BUF_STATE_EMPTY) {
                        rc = sleep_thread(fsg);
                        if (rc)
                                return rc;
                }

                /* If we were asked to read past the end of file,
                 * end with an empty buffer. */
                if (amount == 0) {
                        curlun->sense_data =
                                        SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
                        curlun->sense_data_info = file_offset >> 9;
                        curlun->info_valid = 1;
                        bh->inreq->length = 0;
                        bh->state = BUF_STATE_FULL;
                        break;
                }

                /* Perform the read */
                file_offset_tmp = file_offset;
                nread = vfs_read(curlun->filp,
                                (char __user *) bh->buf,
                                amount, &file_offset_tmp);
                VLDBG(curlun, "file read %u @ %llu -> %d\n", amount,
                                (unsigned long long) file_offset,
                                (int) nread);
                if (signal_pending(current))
                        return -EINTR;

                if (nread < 0) {
                        LDBG(curlun, "error in file read: %d\n",
                                        (int) nread);
                        nread = 0;
                } else if (nread < amount) {
                        LDBG(curlun, "partial file read: %d/%u\n",
                                        (int) nread, amount);
                        nread -= (nread & 511); // Round down to a block
                }
                file_offset  += nread;
                amount_left  -= nread;
                fsg->residue -= nread;
                bh->inreq->length = nread;
                bh->state = BUF_STATE_FULL;

                /* If an error occurred, report it and its position */
                if (nread < amount) {
                        curlun->sense_data = SS_UNRECOVERED_READ_ERROR;
                        curlun->sense_data_info = file_offset >> 9;
                        curlun->info_valid = 1;
                        break;
                }

                if (amount_left == 0)
                        break;          // No more left to read

                /* Send this buffer and go read some more */
                bh->inreq->zero = 0;
                start_transfer(fsg, fsg->bulk_in, bh->inreq,
                                &bh->inreq_busy, &bh->state);
                fsg->next_buffhd_to_fill = bh->next;
        }

        return -EIO;            // No default reply
}


/*-------------------------------------------------------------------------*/

static int do_write(struct fsg_dev *fsg)
{
        struct lun              *curlun = fsg->curlun;
        u32                     lba;
        struct fsg_buffhd       *bh;
        int                     get_some_more;
        u32                     amount_left_to_req, amount_left_to_write;
        loff_t                  usb_offset, file_offset, file_offset_tmp;
        unsigned int            amount;
        unsigned int            partial_page;
        ssize_t                 nwritten;
        int                     rc;

        if (curlun->ro) {
                curlun->sense_data = SS_WRITE_PROTECTED;
                return -EINVAL;
        }
        curlun->filp->f_flags &= ~O_SYNC;       // Default is not to wait

        /* Get the starting Logical Block Address and check that it's
         * not too big */
        if (fsg->cmnd[0] == SC_WRITE_6)
                lba = (fsg->cmnd[1] << 16) | get_be16(&fsg->cmnd[2]);
        else {
                lba = get_be32(&fsg->cmnd[2]);

                /* We allow DPO (Disable Page Out = don't save data in the
                 * cache) and FUA (Force Unit Access = write directly to the
                 * medium).  We don't implement DPO; we implement FUA by
                 * performing synchronous output. */
                if ((fsg->cmnd[1] & ~0x18) != 0) {
                        curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                        return -EINVAL;
                }
                if (fsg->cmnd[1] & 0x08)        // FUA
                        curlun->filp->f_flags |= O_SYNC;
        }
        if (lba >= curlun->num_sectors) {
                curlun->sense_data = SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
                return -EINVAL;
        }

        /* Carry out the file writes */
        get_some_more = 1;
        file_offset = usb_offset = ((loff_t) lba) << 9;
        amount_left_to_req = amount_left_to_write = fsg->data_size_from_cmnd;

        while (amount_left_to_write > 0) {

                /* Queue a request for more data from the host */
                bh = fsg->next_buffhd_to_fill;
                if (bh->state == BUF_STATE_EMPTY && get_some_more) {

                        /* Figure out how much we want to get:
                         * Try to get the remaining amount.
                         * But don't get more than the buffer size.
                         * And don't try to go past the end of the file.
                         * If we're not at a page boundary,
                         *      don't go past the next page.
                         * If this means getting 0, then we were asked
                         *      to write past the end of file.
                         * Finally, round down to a block boundary. */
                        amount = min(amount_left_to_req, mod_data.buflen);
                        amount = min((loff_t) amount, curlun->file_length -
                                        usb_offset);
                        partial_page = usb_offset & (PAGE_CACHE_SIZE - 1);
                        if (partial_page > 0)
                                amount = min(amount,
        (unsigned int) PAGE_CACHE_SIZE - partial_page);

                        if (amount == 0) {
                                get_some_more = 0;
                                curlun->sense_data =
                                        SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
                                curlun->sense_data_info = usb_offset >> 9;
                                curlun->info_valid = 1;
                                continue;
                        }
                        amount -= (amount & 511);
                        if (amount == 0) {

                                /* Why were we were asked to transfer a
                                 * partial block? */
                                get_some_more = 0;
                                continue;
                        }

                        /* Get the next buffer */
                        usb_offset += amount;
                        fsg->usb_amount_left -= amount;
                        amount_left_to_req -= amount;
                        if (amount_left_to_req == 0)
                                get_some_more = 0;

                        /* amount is always divisible by 512, hence by
                         * the bulk-out maxpacket size */
                        bh->outreq->length = bh->bulk_out_intended_length =
                                        amount;
                        bh->outreq->short_not_ok = 1;
                        start_transfer(fsg, fsg->bulk_out, bh->outreq,
                                        &bh->outreq_busy, &bh->state);
                        fsg->next_buffhd_to_fill = bh->next;
                        continue;
                }

                /* Write the received data to the backing file */
                bh = fsg->next_buffhd_to_drain;
                if (bh->state == BUF_STATE_EMPTY && !get_some_more)
                        break;                  // We stopped early
                if (bh->state == BUF_STATE_FULL) {
                        smp_rmb();
                        fsg->next_buffhd_to_drain = bh->next;
                        bh->state = BUF_STATE_EMPTY;

                        /* Did something go wrong with the transfer? */
                        if (bh->outreq->status != 0) {
                                curlun->sense_data = SS_COMMUNICATION_FAILURE;
                                curlun->sense_data_info = file_offset >> 9;
                                curlun->info_valid = 1;
                                break;
                        }

                        amount = bh->outreq->actual;
                        if (curlun->file_length - file_offset < amount) {
                                LERROR(curlun,
        "write %u @ %llu beyond end %llu\n",
        amount, (unsigned long long) file_offset,
        (unsigned long long) curlun->file_length);
                                amount = curlun->file_length - file_offset;
                        }

                        /* Perform the write */
                        file_offset_tmp = file_offset;
                        nwritten = vfs_write(curlun->filp,
                                        (char __user *) bh->buf,
                                        amount, &file_offset_tmp);
                        VLDBG(curlun, "file write %u @ %llu -> %d\n", amount,
                                        (unsigned long long) file_offset,
                                        (int) nwritten);
                        if (signal_pending(current))
                                return -EINTR;          // Interrupted!

                        if (nwritten < 0) {
                                LDBG(curlun, "error in file write: %d\n",
                                                (int) nwritten);
                                nwritten = 0;
                        } else if (nwritten < amount) {
                                LDBG(curlun, "partial file write: %d/%u\n",
                                                (int) nwritten, amount);
                                nwritten -= (nwritten & 511);
                                                // Round down to a block
                        }
                        file_offset += nwritten;
                        amount_left_to_write -= nwritten;
                        fsg->residue -= nwritten;

                        /* If an error occurred, report it and its position */
                        if (nwritten < amount) {
                                curlun->sense_data = SS_WRITE_ERROR;
                                curlun->sense_data_info = file_offset >> 9;
                                curlun->info_valid = 1;
                                break;
                        }

                        /* Did the host decide to stop early? */
                        if (bh->outreq->actual != bh->outreq->length) {
                                fsg->short_packet_received = 1;
                                break;
                        }
                        continue;
                }

                /* Wait for something to happen */
                rc = sleep_thread(fsg);
                if (rc)
                        return rc;
        }

        return -EIO;            // No default reply
}


/*-------------------------------------------------------------------------*/

/* Sync the file data, don't bother with the metadata.
 * This code was copied from fs/buffer.c:sys_fdatasync(). */
static int fsync_sub(struct lun *curlun)
{
        struct file     *filp = curlun->filp;
        struct inode    *inode;
        int             rc, err;

        if (curlun->ro || !filp)
                return 0;
        if (!filp->f_op->fsync)
                return -EINVAL;

        inode = filp->f_path.dentry->d_inode;
        mutex_lock(&inode->i_mutex);
        rc = filemap_fdatawrite(inode->i_mapping);
        err = filp->f_op->fsync(filp, filp->f_path.dentry, 1);
        if (!rc)
                rc = err;
        err = filemap_fdatawait(inode->i_mapping);
        if (!rc)
                rc = err;
        mutex_unlock(&inode->i_mutex);
        VLDBG(curlun, "fdatasync -> %d\n", rc);
        return rc;
}

static void fsync_all(struct fsg_dev *fsg)
{
        int     i;

        for (i = 0; i < fsg->nluns; ++i)
                fsync_sub(&fsg->luns[i]);
}

static int do_synchronize_cache(struct fsg_dev *fsg)
{
        struct lun      *curlun = fsg->curlun;
        int             rc;

        /* We ignore the requested LBA and write out all file's
         * dirty data buffers. */
        rc = fsync_sub(curlun);
        if (rc)
                curlun->sense_data = SS_WRITE_ERROR;
        return 0;
}


/*-------------------------------------------------------------------------*/

static void invalidate_sub(struct lun *curlun)
{
        struct file     *filp = curlun->filp;
        struct inode    *inode = filp->f_path.dentry->d_inode;
        unsigned long   rc;

        rc = invalidate_mapping_pages(inode->i_mapping, 0, -1);
        VLDBG(curlun, "invalidate_inode_pages -> %ld\n", rc);
}

static int do_verify(struct fsg_dev *fsg)
{
        struct lun              *curlun = fsg->curlun;
        u32                     lba;
        u32                     verification_length;
        struct fsg_buffhd       *bh = fsg->next_buffhd_to_fill;
        loff_t                  file_offset, file_offset_tmp;
        u32                     amount_left;
        unsigned int            amount;
        ssize_t                 nread;

        /* Get the starting Logical Block Address and check that it's
         * not too big */
        lba = get_be32(&fsg->cmnd[2]);
        if (lba >= curlun->num_sectors) {
                curlun->sense_data = SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
                return -EINVAL;
        }

        /* We allow DPO (Disable Page Out = don't save data in the
         * cache) but we don't implement it. */
        if ((fsg->cmnd[1] & ~0x10) != 0) {
                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                return -EINVAL;
        }

        verification_length = get_be16(&fsg->cmnd[7]);
        if (unlikely(verification_length == 0))
                return -EIO;            // No default reply

        /* Prepare to carry out the file verify */
        amount_left = verification_length << 9;
        file_offset = ((loff_t) lba) << 9;

        /* Write out all the dirty buffers before invalidating them */
        fsync_sub(curlun);
        if (signal_pending(current))
                return -EINTR;

        invalidate_sub(curlun);
        if (signal_pending(current))
                return -EINTR;

        /* Just try to read the requested blocks */
        while (amount_left > 0) {

                /* Figure out how much we need to read:
                 * Try to read the remaining amount, but not more than
                 * the buffer size.
                 * And don't try to read past the end of the file.
                 * If this means reading 0 then we were asked to read
                 * past the end of file. */
                amount = min((unsigned int) amount_left, mod_data.buflen);
                amount = min((loff_t) amount,
                                curlun->file_length - file_offset);
                if (amount == 0) {
                        curlun->sense_data =
                                        SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
                        curlun->sense_data_info = file_offset >> 9;
                        curlun->info_valid = 1;
                        break;
                }

                /* Perform the read */
                file_offset_tmp = file_offset;
                nread = vfs_read(curlun->filp,
                                (char __user *) bh->buf,
                                amount, &file_offset_tmp);
                VLDBG(curlun, "file read %u @ %llu -> %d\n", amount,
                                (unsigned long long) file_offset,
                                (int) nread);
                if (signal_pending(current))
                        return -EINTR;

                if (nread < 0) {
                        LDBG(curlun, "error in file verify: %d\n",
                                        (int) nread);
                        nread = 0;
                } else if (nread < amount) {
                        LDBG(curlun, "partial file verify: %d/%u\n",
                                        (int) nread, amount);
                        nread -= (nread & 511); // Round down to a sector
                }
                if (nread == 0) {
                        curlun->sense_data = SS_UNRECOVERED_READ_ERROR;
                        curlun->sense_data_info = file_offset >> 9;
                        curlun->info_valid = 1;
                        break;
                }
                file_offset += nread;
                amount_left -= nread;
        }
        return 0;
}


/*-------------------------------------------------------------------------*/

static int do_inquiry(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{
        u8      *buf = (u8 *) bh->buf;

        static char vendor_id[] = "Linux   ";
        static char product_id[] = "File-Stor Gadget";

        if (!fsg->curlun) {             // Unsupported LUNs are okay
                fsg->bad_lun_okay = 1;
                memset(buf, 0, 36);
                buf[0] = 0x7f;          // Unsupported, no device-type
                return 36;
        }

        memset(buf, 0, 8);      // Non-removable, direct-access device
        if (mod_data.removable)
                buf[1] = 0x80;
        buf[2] = 2;             // ANSI SCSI level 2
        buf[3] = 2;             // SCSI-2 INQUIRY data format
        buf[4] = 31;            // Additional length
                                // No special options
        sprintf(buf + 8, "%-8s%-16s%04x", vendor_id, product_id,
                        mod_data.release);
        return 36;
}


static int do_request_sense(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{
        struct lun      *curlun = fsg->curlun;
        u8              *buf = (u8 *) bh->buf;
        u32             sd, sdinfo;
        int             valid;

        /*
         * From the SCSI-2 spec., section 7.9 (Unit attention condition):
         *
         * If a REQUEST SENSE command is received from an initiator
         * with a pending unit attention condition (before the target
         * generates the contingent allegiance condition), then the
         * target shall either:
         *   a) report any pending sense data and preserve the unit
         *      attention condition on the logical unit, or,
         *   b) report the unit attention condition, may discard any
         *      pending sense data, and clear the unit attention
         *      condition on the logical unit for that initiator.
         *
         * FSG normally uses option a); enable this code to use option b).
         */
#if 0
        if (curlun && curlun->unit_attention_data != SS_NO_SENSE) {
                curlun->sense_data = curlun->unit_attention_data;
                curlun->unit_attention_data = SS_NO_SENSE;
        }
#endif

        if (!curlun) {          // Unsupported LUNs are okay
                fsg->bad_lun_okay = 1;
                sd = SS_LOGICAL_UNIT_NOT_SUPPORTED;
                sdinfo = 0;
                valid = 0;
        } else {
                sd = curlun->sense_data;
                sdinfo = curlun->sense_data_info;
                valid = curlun->info_valid << 7;
                curlun->sense_data = SS_NO_SENSE;
                curlun->sense_data_info = 0;
                curlun->info_valid = 0;
        }

        memset(buf, 0, 18);
        buf[0] = valid | 0x70;                  // Valid, current error
        buf[2] = SK(sd);
        put_be32(&buf[3], sdinfo);              // Sense information
        buf[7] = 18 - 8;                        // Additional sense length
        buf[12] = ASC(sd);
        buf[13] = ASCQ(sd);
        return 18;
}


static int do_read_capacity(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{
        struct lun      *curlun = fsg->curlun;
        u32             lba = get_be32(&fsg->cmnd[2]);
        int             pmi = fsg->cmnd[8];
        u8              *buf = (u8 *) bh->buf;

        /* Check the PMI and LBA fields */
        if (pmi > 1 || (pmi == 0 && lba != 0)) {
                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                return -EINVAL;
        }

        put_be32(&buf[0], curlun->num_sectors - 1);     // Max logical block
        put_be32(&buf[4], 512);                         // Block length
        return 8;
}


static int do_mode_sense(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{
        struct lun      *curlun = fsg->curlun;
        int             mscmnd = fsg->cmnd[0];
        u8              *buf = (u8 *) bh->buf;
        u8              *buf0 = buf;
        int             pc, page_code;
        int             changeable_values, all_pages;
        int             valid_page = 0;
        int             len, limit;

        if ((fsg->cmnd[1] & ~0x08) != 0) {              // Mask away DBD
                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                return -EINVAL;
        }
        pc = fsg->cmnd[2] >> 6;
        page_code = fsg->cmnd[2] & 0x3f;
        if (pc == 3) {
                curlun->sense_data = SS_SAVING_PARAMETERS_NOT_SUPPORTED;
                return -EINVAL;
        }
        changeable_values = (pc == 1);
        all_pages = (page_code == 0x3f);

        /* Write the mode parameter header.  Fixed values are: default
         * medium type, no cache control (DPOFUA), and no block descriptors.
         * The only variable value is the WriteProtect bit.  We will fill in
         * the mode data length later. */
        memset(buf, 0, 8);
        if (mscmnd == SC_MODE_SENSE_6) {
                buf[2] = (curlun->ro ? 0x80 : 0x00);            // WP, DPOFUA
                buf += 4;
                limit = 255;
        } else {                        // SC_MODE_SENSE_10
                buf[3] = (curlun->ro ? 0x80 : 0x00);            // WP, DPOFUA
                buf += 8;
                limit = 65535;          // Should really be mod_data.buflen
        }

        /* No block descriptors */

        /* The mode pages, in numerical order.  The only page we support
         * is the Caching page. */
        if (page_code == 0x08 || all_pages) {
                valid_page = 1;
                buf[0] = 0x08;          // Page code
                buf[1] = 10;            // Page length
                memset(buf+2, 0, 10);   // None of the fields are changeable

                if (!changeable_values) {
                        buf[2] = 0x04;  // Write cache enable,
                                        // Read cache not disabled
                                        // No cache retention priorities
                        put_be16(&buf[4], 0xffff);  // Don't disable prefetch
                                        // Minimum prefetch = 0
                        put_be16(&buf[8], 0xffff);  // Maximum prefetch
                        put_be16(&buf[10], 0xffff); // Maximum prefetch ceiling
                }
                buf += 12;
        }

        /* Check that a valid page was requested and the mode data length
         * isn't too long. */
        len = buf - buf0;
        if (!valid_page || len > limit) {
                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                return -EINVAL;
        }

        /*  Store the mode data length */
        if (mscmnd == SC_MODE_SENSE_6)
                buf0[0] = len - 1;
        else
                put_be16(buf0, len - 2);
        return len;
}


static int do_start_stop(struct fsg_dev *fsg)
{
        struct lun      *curlun = fsg->curlun;
        int             loej, start;

        if (!mod_data.removable) {
                curlun->sense_data = SS_INVALID_COMMAND;
                return -EINVAL;
        }

        // int immed = fsg->cmnd[1] & 0x01;
        loej = fsg->cmnd[4] & 0x02;
        start = fsg->cmnd[4] & 0x01;

#ifdef CONFIG_USB_FILE_STORAGE_TEST
        if ((fsg->cmnd[1] & ~0x01) != 0 ||              // Mask away Immed
                        (fsg->cmnd[4] & ~0x03) != 0) {  // Mask LoEj, Start
                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                return -EINVAL;
        }

        if (!start) {

                /* Are we allowed to unload the media? */
                if (curlun->prevent_medium_removal) {
                        LDBG(curlun, "unload attempt prevented\n");
                        curlun->sense_data = SS_MEDIUM_REMOVAL_PREVENTED;
                        return -EINVAL;
                }
                if (loej) {             // Simulate an unload/eject
                        up_read(&fsg->filesem);
                        down_write(&fsg->filesem);
                        close_backing_file(curlun);
                        up_write(&fsg->filesem);
                        down_read(&fsg->filesem);
                }
        } else {

                /* Our emulation doesn't support mounting; the medium is
                 * available for use as soon as it is loaded. */
                if (!backing_file_is_open(curlun)) {
                        curlun->sense_data = SS_MEDIUM_NOT_PRESENT;
                        return -EINVAL;
                }
        }
#endif
        return 0;
}


static int do_prevent_allow(struct fsg_dev *fsg)
{
        struct lun      *curlun = fsg->curlun;
        int             prevent;

        if (!mod_data.removable) {
                curlun->sense_data = SS_INVALID_COMMAND;
                return -EINVAL;
        }

        prevent = fsg->cmnd[4] & 0x01;
        if ((fsg->cmnd[4] & ~0x01) != 0) {              // Mask away Prevent
                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                return -EINVAL;
        }

        if (curlun->prevent_medium_removal && !prevent)
                fsync_sub(curlun);
        curlun->prevent_medium_removal = prevent;
        return 0;
}


static int do_read_format_capacities(struct fsg_dev *fsg,
                        struct fsg_buffhd *bh)
{
        struct lun      *curlun = fsg->curlun;
        u8              *buf = (u8 *) bh->buf;

        buf[0] = buf[1] = buf[2] = 0;
        buf[3] = 8;             // Only the Current/Maximum Capacity Descriptor
        buf += 4;

        put_be32(&buf[0], curlun->num_sectors);         // Number of blocks
        put_be32(&buf[4], 512);                         // Block length
        buf[4] = 0x02;                                  // Current capacity
        return 12;
}


static int do_mode_select(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{
        struct lun      *curlun = fsg->curlun;

        /* We don't support MODE SELECT */
        curlun->sense_data = SS_INVALID_COMMAND;
        return -EINVAL;
}


/*-------------------------------------------------------------------------*/

static int halt_bulk_in_endpoint(struct fsg_dev *fsg)
{
        int     rc;

        rc = fsg_set_halt(fsg, fsg->bulk_in);
        if (rc == -EAGAIN)
                VDBG(fsg, "delayed bulk-in endpoint halt\n");
        while (rc != 0) {
                if (rc != -EAGAIN) {
                        WARN(fsg, "usb_ep_set_halt -> %d\n", rc);
                        rc = 0;
                        break;
                }

                /* Wait for a short time and then try again */
                if (msleep_interruptible(100) != 0)
                        return -EINTR;
                rc = usb_ep_set_halt(fsg->bulk_in);
        }
        return rc;
}

static int pad_with_zeros(struct fsg_dev *fsg)
{
        struct fsg_buffhd       *bh = fsg->next_buffhd_to_fill;
        u32                     nkeep = bh->inreq->length;
        u32                     nsend;
        int                     rc;

        bh->state = BUF_STATE_EMPTY;            // For the first iteration
        fsg->usb_amount_left = nkeep + fsg->residue;
        while (fsg->usb_amount_left > 0) {

                /* Wait for the next buffer to be free */
                while (bh->state != BUF_STATE_EMPTY) {
                        rc = sleep_thread(fsg);
                        if (rc)
                                return rc;
                }

                nsend = min(fsg->usb_amount_left, (u32) mod_data.buflen);
                memset(bh->buf + nkeep, 0, nsend - nkeep);
                bh->inreq->length = nsend;
                bh->inreq->zero = 0;
                start_transfer(fsg, fsg->bulk_in, bh->inreq,
                                &bh->inreq_busy, &bh->state);
                bh = fsg->next_buffhd_to_fill = bh->next;
                fsg->usb_amount_left -= nsend;
                nkeep = 0;
        }
        return 0;
}

static int throw_away_data(struct fsg_dev *fsg)
{
        struct fsg_buffhd       *bh;
        u32                     amount;
        int                     rc;

        while ((bh = fsg->next_buffhd_to_drain)->state != BUF_STATE_EMPTY ||
                        fsg->usb_amount_left > 0) {

                /* Throw away the data in a filled buffer */
                if (bh->state == BUF_STATE_FULL) {
                        smp_rmb();
                        bh->state = BUF_STATE_EMPTY;
                        fsg->next_buffhd_to_drain = bh->next;

                        /* A short packet or an error ends everything */
                        if (bh->outreq->actual != bh->outreq->length ||
                                        bh->outreq->status != 0) {
                                raise_exception(fsg, FSG_STATE_ABORT_BULK_OUT);
                                return -EINTR;
                        }
                        continue;
                }

                /* Try to submit another request if we need one */
                bh = fsg->next_buffhd_to_fill;
                if (bh->state == BUF_STATE_EMPTY && fsg->usb_amount_left > 0) {
                        amount = min(fsg->usb_amount_left,
                                        (u32) mod_data.buflen);

                        /* amount is always divisible by 512, hence by
                         * the bulk-out maxpacket size */
                        bh->outreq->length = bh->bulk_out_intended_length =
                                        amount;
                        bh->outreq->short_not_ok = 1;
                        start_transfer(fsg, fsg->bulk_out, bh->outreq,
                                        &bh->outreq_busy, &bh->state);
                        fsg->next_buffhd_to_fill = bh->next;
                        fsg->usb_amount_left -= amount;
                        continue;
                }

                /* Otherwise wait for something to happen */
                rc = sleep_thread(fsg);
                if (rc)
                        return rc;
        }
        return 0;
}


static int finish_reply(struct fsg_dev *fsg)
{
        struct fsg_buffhd       *bh = fsg->next_buffhd_to_fill;
        int                     rc = 0;

        switch (fsg->data_dir) {
        case DATA_DIR_NONE:
                break;                  // Nothing to send

        /* If we don't know whether the host wants to read or write,
         * this must be CB or CBI with an unknown command.  We mustn't
         * try to send or receive any data.  So stall both bulk pipes
         * if we can and wait for a reset. */
        case DATA_DIR_UNKNOWN:
                if (mod_data.can_stall) {
                        fsg_set_halt(fsg, fsg->bulk_out);
                        rc = halt_bulk_in_endpoint(fsg);
                }
                break;

        /* All but the last buffer of data must have already been sent */
        case DATA_DIR_TO_HOST:
                if (fsg->data_size == 0)
                        ;               // Nothing to send

                /* If there's no residue, simply send the last buffer */
                else if (fsg->residue == 0) {
                        bh->inreq->zero = 0;
                        start_transfer(fsg, fsg->bulk_in, bh->inreq,
                                        &bh->inreq_busy, &bh->state);
                        fsg->next_buffhd_to_fill = bh->next;
                }

                /* There is a residue.  For CB and CBI, simply mark the end
                 * of the data with a short packet.  However, if we are
                 * allowed to stall, there was no data at all (residue ==
                 * data_size), and the command failed (invalid LUN or
                 * sense data is set), then halt the bulk-in endpoint
                 * instead. */
                else if (!transport_is_bbb()) {
                        if (mod_data.can_stall &&
                                        fsg->residue == fsg->data_size &&
        (!fsg->curlun || fsg->curlun->sense_data != SS_NO_SENSE)) {
                                bh->state = BUF_STATE_EMPTY;
                                rc = halt_bulk_in_endpoint(fsg);
                        } else {
                                bh->inreq->zero = 1;
                                start_transfer(fsg, fsg->bulk_in, bh->inreq,
                                                &bh->inreq_busy, &bh->state);
                                fsg->next_buffhd_to_fill = bh->next;
                        }
                }

                /* For Bulk-only, if we're allowed to stall then send the
                 * short packet and halt the bulk-in endpoint.  If we can't
                 * stall, pad out the remaining data with 0's. */
                else {
                        if (mod_data.can_stall) {
                                bh->inreq->zero = 1;
                                start_transfer(fsg, fsg->bulk_in, bh->inreq,
                                                &bh->inreq_busy, &bh->state);
                                fsg->next_buffhd_to_fill = bh->next;
                                rc = halt_bulk_in_endpoint(fsg);
                        } else
                                rc = pad_with_zeros(fsg);
                }
                break;

        /* We have processed all we want from the data the host has sent.
         * There may still be outstanding bulk-out requests. */
        case DATA_DIR_FROM_HOST:
                if (fsg->residue == 0)
                        ;               // Nothing to receive

                /* Did the host stop sending unexpectedly early? */
                else if (fsg->short_packet_received) {
                        raise_exception(fsg, FSG_STATE_ABORT_BULK_OUT);
                        rc = -EINTR;
                }

                /* We haven't processed all the incoming data.  Even though
                 * we may be allowed to stall, doing so would cause a race.
                 * The controller may already have ACK'ed all the remaining
                 * bulk-out packets, in which case the host wouldn't see a
                 * STALL.  Not realizing the endpoint was halted, it wouldn't
                 * clear the halt -- leading to problems later on. */
#if 0
                else if (mod_data.can_stall) {
                        fsg_set_halt(fsg, fsg->bulk_out);
                        raise_exception(fsg, FSG_STATE_ABORT_BULK_OUT);
                        rc = -EINTR;
                }
#endif

                /* We can't stall.  Read in the excess data and throw it
                 * all away. */
                else
                        rc = throw_away_data(fsg);
                break;
        }
        return rc;
}


static int send_status(struct fsg_dev *fsg)
{
        struct lun              *curlun = fsg->curlun;
        struct fsg_buffhd       *bh;
        int                     rc;
        u8                      status = USB_STATUS_PASS;
        u32                     sd, sdinfo = 0;

        /* Wait for the next buffer to become available */
        bh = fsg->next_buffhd_to_fill;
        while (bh->state != BUF_STATE_EMPTY) {
                rc = sleep_thread(fsg);
                if (rc)
                        return rc;
        }

        if (curlun) {
                sd = curlun->sense_data;
                sdinfo = curlun->sense_data_info;
        } else if (fsg->bad_lun_okay)
                sd = SS_NO_SENSE;
        else
                sd = SS_LOGICAL_UNIT_NOT_SUPPORTED;

        if (fsg->phase_error) {
                DBG(fsg, "sending phase-error status\n");
                status = USB_STATUS_PHASE_ERROR;
                sd = SS_INVALID_COMMAND;
        } else if (sd != SS_NO_SENSE) {
                DBG(fsg, "sending command-failure status\n");
                status = USB_STATUS_FAIL;
                VDBG(fsg, "  sense data: SK x%02x, ASC x%02x, ASCQ x%02x;"
                                "  info x%x\n",
                                SK(sd), ASC(sd), ASCQ(sd), sdinfo);
        }

        if (transport_is_bbb()) {
                struct bulk_cs_wrap     *csw = bh->buf;

                /* Store and send the Bulk-only CSW */
                csw->Signature = __constant_cpu_to_le32(USB_BULK_CS_SIG);
                csw->Tag = fsg->tag;
                csw->Residue = cpu_to_le32(fsg->residue);
                csw->Status = status;

                bh->inreq->length = USB_BULK_CS_WRAP_LEN;
                bh->inreq->zero = 0;
                start_transfer(fsg, fsg->bulk_in, bh->inreq,
                                &bh->inreq_busy, &bh->state);

        } else if (mod_data.transport_type == USB_PR_CB) {

                /* Control-Bulk transport has no status phase! */
                return 0;

        } else {                        // USB_PR_CBI
                struct interrupt_data   *buf = bh->buf;

                /* Store and send the Interrupt data.  UFI sends the ASC
                 * and ASCQ bytes.  Everything else sends a Type (which
                 * is always 0) and the status Value. */
                if (mod_data.protocol_type == USB_SC_UFI) {
                        buf->bType = ASC(sd);
                        buf->bValue = ASCQ(sd);
                } else {
                        buf->bType = 0;
                        buf->bValue = status;
                }
                fsg->intreq->length = CBI_INTERRUPT_DATA_LEN;

                fsg->intr_buffhd = bh;          // Point to the right buffhd
                fsg->intreq->buf = bh->inreq->buf;
                fsg->intreq->context = bh;
                start_transfer(fsg, fsg->intr_in, fsg->intreq,
                                &fsg->intreq_busy, &bh->state);
        }

        fsg->next_buffhd_to_fill = bh->next;
        return 0;
}


/*-------------------------------------------------------------------------*/

/* Check whether the command is properly formed and whether its data size
 * and direction agree with the values we already have. */
static int check_command(struct fsg_dev *fsg, int cmnd_size,
                enum data_direction data_dir, unsigned int mask,
                int needs_medium, const char *name)
{
        int                     i;
        int                     lun = fsg->cmnd[1] >> 5;
        static const char       dirletter[4] = {'u', 'o', 'i', 'n'};
        char                    hdlen[20];
        struct lun              *curlun;

        /* Adjust the expected cmnd_size for protocol encapsulation padding.
         * Transparent SCSI doesn't pad. */
        if (protocol_is_scsi())
                ;

        /* There's some disagreement as to whether RBC pads commands or not.
         * We'll play it safe and accept either form. */
        else if (mod_data.protocol_type == USB_SC_RBC) {
                if (fsg->cmnd_size == 12)
                        cmnd_size = 12;

        /* All the other protocols pad to 12 bytes */
        } else
                cmnd_size = 12;

        hdlen[0] = 0;
        if (fsg->data_dir != DATA_DIR_UNKNOWN)
                sprintf(hdlen, ", H%c=%u", dirletter[(int) fsg->data_dir],
                                fsg->data_size);
        VDBG(fsg, "SCSI command: %s;  Dc=%d, D%c=%u;  Hc=%d%s\n",
                        name, cmnd_size, dirletter[(int) data_dir],
                        fsg->data_size_from_cmnd, fsg->cmnd_size, hdlen);

        /* We can't reply at all until we know the correct data direction
         * and size. */
        if (fsg->data_size_from_cmnd == 0)
                data_dir = DATA_DIR_NONE;
        if (fsg->data_dir == DATA_DIR_UNKNOWN) {        // CB or CBI
                fsg->data_dir = data_dir;
                fsg->data_size = fsg->data_size_from_cmnd;

        } else {                                        // Bulk-only
                if (fsg->data_size < fsg->data_size_from_cmnd) {

                        /* Host data size < Device data size is a phase error.
                         * Carry out the command, but only transfer as much
                         * as we are allowed. */
                        fsg->data_size_from_cmnd = fsg->data_size;
                        fsg->phase_error = 1;
                }
        }
        fsg->residue = fsg->usb_amount_left = fsg->data_size;

        /* Conflicting data directions is a phase error */
        if (fsg->data_dir != data_dir && fsg->data_size_from_cmnd > 0) {
                fsg->phase_error = 1;
                return -EINVAL;
        }

        /* Verify the length of the command itself */
        if (cmnd_size != fsg->cmnd_size) {

                /* Special case workaround: MS-Windows issues REQUEST SENSE
                 * with cbw->Length == 12 (it should be 6). */
                if (fsg->cmnd[0] == SC_REQUEST_SENSE && fsg->cmnd_size == 12)
                        cmnd_size = fsg->cmnd_size;
                else {
                        fsg->phase_error = 1;
                        return -EINVAL;
                }
        }

        /* Check that the LUN values are consistent */
        if (transport_is_bbb()) {
                if (fsg->lun != lun)
                        DBG(fsg, "using LUN %d from CBW, "
                                        "not LUN %d from CDB\n",
                                        fsg->lun, lun);
        } else
                fsg->lun = lun;         // Use LUN from the command

        /* Check the LUN */
        if (fsg->lun >= 0 && fsg->lun < fsg->nluns) {
                fsg->curlun = curlun = &fsg->luns[fsg->lun];
                if (fsg->cmnd[0] != SC_REQUEST_SENSE) {
                        curlun->sense_data = SS_NO_SENSE;
                        curlun->sense_data_info = 0;
                        curlun->info_valid = 0;
                }
        } else {
                fsg->curlun = curlun = NULL;
                fsg->bad_lun_okay = 0;

                /* INQUIRY and REQUEST SENSE commands are explicitly allowed
                 * to use unsupported LUNs; all others may not. */
                if (fsg->cmnd[0] != SC_INQUIRY &&
                                fsg->cmnd[0] != SC_REQUEST_SENSE) {
                        DBG(fsg, "unsupported LUN %d\n", fsg->lun);
                        return -EINVAL;
                }
        }

        /* If a unit attention condition exists, only INQUIRY and
         * REQUEST SENSE commands are allowed; anything else must fail. */
        if (curlun && curlun->unit_attention_data != SS_NO_SENSE &&
                        fsg->cmnd[0] != SC_INQUIRY &&
                        fsg->cmnd[0] != SC_REQUEST_SENSE) {
                curlun->sense_data = curlun->unit_attention_data;
                curlun->unit_attention_data = SS_NO_SENSE;
                return -EINVAL;
        }

        /* Check that only command bytes listed in the mask are non-zero */
        fsg->cmnd[1] &= 0x1f;                   // Mask away the LUN
        for (i = 1; i < cmnd_size; ++i) {
                if (fsg->cmnd[i] && !(mask & (1 << i))) {
                        if (curlun)
                                curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
                        return -EINVAL;
                }
        }

        /* If the medium isn't mounted and the command needs to access
         * it, return an error. */
        if (curlun && !backing_file_is_open(curlun) && needs_medium) {
                curlun->sense_data = SS_MEDIUM_NOT_PRESENT;
                return -EINVAL;
        }

        return 0;
}


static int do_scsi_command(struct fsg_dev *fsg)
{
        struct fsg_buffhd       *bh;
        int                     rc;
        int                     reply = -EINVAL;
        int                     i;
        static char             unknown[16];

        dump_cdb(fsg);

        /* Wait for the next buffer to become available for data or status */
        bh = fsg->next_buffhd_to_drain = fsg->next_buffhd_to_fill;
        while (bh->state != BUF_STATE_EMPTY) {
                rc = sleep_thread(fsg);
                if (rc)
                        return rc;
        }
        fsg->phase_error = 0;
        fsg->short_packet_received = 0;

        down_read(&fsg->filesem);       // We're using the backing file
        switch (fsg->cmnd[0]) {

        case SC_INQUIRY:
                fsg->data_size_from_cmnd = fsg->cmnd[4];
                if ((reply = check_command(fsg, 6, DATA_DIR_TO_HOST,
                                (1<<4), 0,
                                "INQUIRY")) == 0)
                        reply = do_inquiry(fsg, bh);
                break;

        case SC_MODE_SELECT_6:
                fsg->data_size_from_cmnd = fsg->cmnd[4];
                if ((reply = check_command(fsg, 6, DATA_DIR_FROM_HOST,
                                (1<<1) | (1<<4), 0,
                                "MODE SELECT(6)")) == 0)
                        reply = do_mode_select(fsg, bh);
                break;

        case SC_MODE_SELECT_10:
                fsg->data_size_from_cmnd = get_be16(&fsg->cmnd[7]);
                if ((reply = check_command(fsg, 10, DATA_DIR_FROM_HOST,
                                (1<<1) | (3<<7), 0,
                                "MODE SELECT(10)")) == 0)
                        reply = do_mode_select(fsg, bh);
                break;

        case SC_MODE_SENSE_6:
                fsg->data_size_from_cmnd = fsg->cmnd[4];
                if ((reply = check_command(fsg, 6, DATA_DIR_TO_HOST,
                                (1<<1) | (1<<2) | (1<<4), 0,
                                "MODE SENSE(6)")) == 0)
                        reply = do_mode_sense(fsg, bh);
                break;

        case SC_MODE_SENSE_10:
                fsg->data_size_from_cmnd = get_be16(&fsg->cmnd[7]);
                if ((reply = check_command(fsg, 10, DATA_DIR_TO_HOST,
                                (1<<1) | (1<<2) | (3<<7), 0,
                                "MODE SENSE(10)")) == 0)
                        reply = do_mode_sense(fsg, bh);
                break;

        case SC_PREVENT_ALLOW_MEDIUM_REMOVAL:
                fsg->data_size_from_cmnd = 0;
                if ((reply = check_command(fsg, 6, DATA_DIR_NONE,
                                (1<<4), 0,
                                "PREVENT-ALLOW MEDIUM REMOVAL")) == 0)
                        reply = do_prevent_allow(fsg);
                break;

        case SC_READ_6:
                i = fsg->cmnd[4];
                fsg->data_size_from_cmnd = (i == 0 ? 256 : i) << 9;
                if ((reply = check_command(fsg, 6, DATA_DIR_TO_HOST,
                                (7<<1) | (1<<4), 1,
                                "READ(6)")) == 0)
                        reply = do_read(fsg);
                break;

        case SC_READ_10:
                fsg->data_size_from_cmnd = get_be16(&fsg->cmnd[7]) << 9;
                if ((reply = check_command(fsg, 10, DATA_DIR_TO_HOST,
                                (1<<1) | (0xf<<2) | (3<<7), 1,
                                "READ(10)")) == 0)
                        reply = do_read(fsg);
                break;

        case SC_READ_12:
                fsg->data_size_from_cmnd = get_be32(&fsg->cmnd[6]) << 9;
                if ((reply = check_command(fsg, 12, DATA_DIR_TO_HOST,
                                (1<<1) | (0xf<<2) | (0xf<<6), 1,
                                "READ(12)")) == 0)
                        reply = do_read(fsg);
                break;

        case SC_READ_CAPACITY:
                fsg->data_size_from_cmnd = 8;
                if ((reply = check_command(fsg, 10, DATA_DIR_TO_HOST,
                                (0xf<<2) | (1<<8), 1,
                                "READ CAPACITY")) == 0)
                        reply = do_read_capacity(fsg, bh);
                break;

        case SC_READ_FORMAT_CAPACITIES:
                fsg->data_size_from_cmnd = get_be16(&fsg->cmnd[7]);
                if ((reply = check_command(fsg, 10, DATA_DIR_TO_HOST,
                                (3<<7), 1,
                                "READ FORMAT CAPACITIES")) == 0)
                        reply = do_read_format_capacities(fsg, bh);
                break;

        case SC_REQUEST_SENSE:
                fsg->data_size_from_cmnd = fsg->cmnd[4];
                if ((reply = check_command(fsg, 6, DATA_DIR_TO_HOST,
                                (1<<4), 0,
                                "REQUEST SENSE")) == 0)
                        reply = do_request_sense(fsg, bh);
                break;

        case SC_START_STOP_UNIT:
                fsg->data_size_from_cmnd = 0;
                if ((reply = check_command(fsg, 6, DATA_DIR_NONE,
                                (1<<1) | (1<<4), 0,
                                "START-STOP UNIT")) == 0)
                        reply = do_start_stop(fsg);
                break;

        case SC_SYNCHRONIZE_CACHE:
                fsg->data_size_from_cmnd = 0;
                if ((reply = check_command(fsg, 10, DATA_DIR_NONE,
                                (0xf<<2) | (3<<7), 1,
                                "SYNCHRONIZE CACHE")) == 0)
                        reply = do_synchronize_cache(fsg);
                break;

        case SC_TEST_UNIT_READY:
                fsg->data_size_from_cmnd = 0;
                reply = check_command(fsg, 6, DATA_DIR_NONE,
                                0, 1,
                                "TEST UNIT READY");
                break;

        /* Although optional, this command is used by MS-Windows.  We
         * support a minimal version: BytChk must be 0. */
        case SC_VERIFY:
                fsg->data_size_from_cmnd = 0;
                if ((reply = check_command(fsg, 10, DATA_DIR_NONE,
                                (1<<1) | (0xf<<2) | (3<<7), 1,
                                "VERIFY")) == 0)
                        reply = do_verify(fsg);
                break;

        case SC_WRITE_6:
                i = fsg->cmnd[4];
                fsg->data_size_from_cmnd = (i == 0 ? 256 : i) << 9;
                if ((reply = check_command(fsg, 6, DATA_DIR_FROM_HOST,
                                (7<<1) | (1<<4), 1,
                                "WRITE(6)")) == 0)
                        reply = do_write(fsg);
                break;

        case SC_WRITE_10:
                fsg->data_size_from_cmnd = get_be16(&fsg->cmnd[7]) << 9;
                if ((reply = check_command(fsg, 10, DATA_DIR_FROM_HOST,
                                (1<<1) | (0xf<<2) | (3<<7), 1,
                                "WRITE(10)")) == 0)
                        reply = do_write(fsg);
                break;

        case SC_WRITE_12:
                fsg->data_size_from_cmnd = get_be32(&fsg->cmnd[6]) << 9;
                if ((reply = check_command(fsg, 12, DATA_DIR_FROM_HOST,
                                (1<<1) | (0xf<<2) | (0xf<<6), 1,
                                "WRITE(12)")) == 0)
                        reply = do_write(fsg);
                break;

        /* Some mandatory commands that we recognize but don't implement.
         * They don't mean much in this setting.  It's left as an exercise
         * for anyone interested to implement RESERVE and RELEASE in terms
         * of Posix locks. */
        case SC_FORMAT_UNIT:
        case SC_RELEASE:
        case SC_RESERVE:
        case SC_SEND_DIAGNOSTIC:
                // Fall through

        default:
                fsg->data_size_from_cmnd = 0;
                sprintf(unknown, "Unknown x%02x", fsg->cmnd[0]);
                if ((reply = check_command(fsg, fsg->cmnd_size,
                                DATA_DIR_UNKNOWN, 0xff, 0, unknown)) == 0) {
                        fsg->curlun->sense_data = SS_INVALID_COMMAND;
                        reply = -EINVAL;
                }
                break;
        }
        up_read(&fsg->filesem);

        if (reply == -EINTR || signal_pending(current))
                return -EINTR;

        /* Set up the single reply buffer for finish_reply() */
        if (reply == -EINVAL)
                reply = 0;              // Error reply length
        if (reply >= 0 && fsg->data_dir == DATA_DIR_TO_HOST) {
                reply = min((u32) reply, fsg->data_size_from_cmnd);
                bh->inreq->length = reply;
                bh->state = BUF_STATE_FULL;
                fsg->residue -= reply;
        }                               // Otherwise it's already set

        return 0;
}


/*-------------------------------------------------------------------------*/

static int received_cbw(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{
        struct usb_request      *req = bh->outreq;
        struct bulk_cb_wrap     *cbw = req->buf;

        /* Was this a real packet? */
        if (req->status)
                return -EINVAL;

        /* Is the CBW valid? */
        if (req->actual != USB_BULK_CB_WRAP_LEN ||
                        cbw->Signature != __constant_cpu_to_le32(
                                USB_BULK_CB_SIG)) {
                DBG(fsg, "invalid CBW: len %u sig 0x%x\n",
                                req->actual,
                                le32_to_cpu(cbw->Signature));

                /* The Bulk-only spec says we MUST stall the bulk pipes!
                 * If we want to avoid stalls, set a flag so that we will
                 * clear the endpoint halts at the next reset. */
                if (!mod_data.can_stall)
                        set_bit(CLEAR_BULK_HALTS, &fsg->atomic_bitflags);
                fsg_set_halt(fsg, fsg->bulk_out);
                halt_bulk_in_endpoint(fsg);
                return -EINVAL;
        }

        /* Is the CBW meaningful? */
        if (cbw->Lun >= MAX_LUNS || cbw->Flags & ~USB_BULK_IN_FLAG ||
                        cbw->Length <= 0 || cbw->Length > MAX_COMMAND_SIZE) {
                DBG(fsg, "non-meaningful CBW: lun = %u, flags = 0x%x, "
                                "cmdlen %u\n",
                                cbw->Lun, cbw->Flags, cbw->Length);

                /* We can do anything we want here, so let's stall the
                 * bulk pipes if we are allowed to. */
                if (mod_data.can_stall) {
                        fsg_set_halt(fsg, fsg->bulk_out);
                        halt_bulk_in_endpoint(fsg);
                }
                return -EINVAL;
        }

        /* Save the command for later */
        fsg->cmnd_size = cbw->Length;
        memcpy(fsg->cmnd, cbw->CDB, fsg->cmnd_size);
        if (cbw->Flags & USB_BULK_IN_FLAG)
                fsg->data_dir = DATA_DIR_TO_HOST;
        else
                fsg->data_dir = DATA_DIR_FROM_HOST;
        fsg->data_size = le32_to_cpu(cbw->DataTransferLength);
        if (fsg->data_size == 0)
                fsg->data_dir = DATA_DIR_NONE;
        fsg->lun = cbw->Lun;
        fsg->tag = cbw->Tag;
        return 0;
}


static int get_next_command(struct fsg_dev *fsg)
{
        struct fsg_buffhd       *bh;
        int                     rc = 0;

        if (transport_is_bbb()) {

                /* Wait for the next buffer to become available */
                bh = fsg->next_buffhd_to_fill;
                while (bh->state != BUF_STATE_EMPTY) {
                        rc = sleep_thread(fsg);
                        if (rc)
                                return rc;
                }

                /* Queue a request to read a Bulk-only CBW */
                set_bulk_out_req_length(fsg, bh, USB_BULK_CB_WRAP_LEN);
                bh->outreq->short_not_ok = 1;
                start_transfer(fsg, fsg->bulk_out, bh->outreq,
                                &bh->outreq_busy, &bh->state);

                /* We will drain the buffer in software, which means we
                 * can reuse it for the next filling.  No need to advance
                 * next_buffhd_to_fill. */

                /* Wait for the CBW to arrive */
                while (bh->state != BUF_STATE_FULL) {
                        rc = sleep_thread(fsg);
                        if (rc)
                                return rc;
                }
                smp_rmb();
                rc = received_cbw(fsg, bh);
                bh->state = BUF_STATE_EMPTY;

        } else {                // USB_PR_CB or USB_PR_CBI

                /* Wait for the next command to arrive */
                while (fsg->cbbuf_cmnd_size == 0) {
                        rc = sleep_thread(fsg);
                        if (rc)
                                return rc;
                }

                /* Is the previous status interrupt request still busy?
                 * The host is allowed to skip reading the status,
                 * so we must cancel it. */
                if (fsg->intreq_busy)
                        usb_ep_dequeue(fsg->intr_in, fsg->intreq);

                /* Copy the command and mark the buffer empty */
                fsg->data_dir = DATA_DIR_UNKNOWN;
                spin_lock_irq(&fsg->lock);
                fsg->cmnd_size = fsg->cbbuf_cmnd_size;
                memcpy(fsg->cmnd, fsg->cbbuf_cmnd, fsg->cmnd_size);
                fsg->cbbuf_cmnd_size = 0;
                spin_unlock_irq(&fsg->lock);
        }
        return rc;
}


/*-------------------------------------------------------------------------*/

static int enable_endpoint(struct fsg_dev *fsg, struct usb_ep *ep,
                const struct usb_endpoint_descriptor *d)
{
        int     rc;

        ep->driver_data = fsg;
        rc = usb_ep_enable(ep, d);
        if (rc)
                ERROR(fsg, "can't enable %s, result %d\n", ep->name, rc);
        return rc;
}

static int alloc_request(struct fsg_dev *fsg, struct usb_ep *ep,
                struct usb_request **preq)
{
        *preq = usb_ep_alloc_request(ep, GFP_ATOMIC);
        if (*preq)
                return 0;
        ERROR(fsg, "can't allocate request for %s\n", ep->name);
        return -ENOMEM;
}

/*
 * Reset interface setting and re-init endpoint state (toggle etc).
 * Call with altsetting < 0 to disable the interface.  The only other
 * available altsetting is 0, which enables the interface.
 */
static int do_set_interface(struct fsg_dev *fsg, int altsetting)
{
        int     rc = 0;
        int     i;
        const struct usb_endpoint_descriptor    *d;

        if (fsg->running)
                DBG(fsg, "reset interface\n");

reset:
        /* Deallocate the requests */
        for (i = 0; i < NUM_BUFFERS; ++i) {
                struct fsg_buffhd *bh = &fsg->buffhds[i];

                if (bh->inreq) {
                        usb_ep_free_request(fsg->bulk_in, bh->inreq);
                        bh->inreq = NULL;
                }
                if (bh->outreq) {
                        usb_ep_free_request(fsg->bulk_out, bh->outreq);
                        bh->outreq = NULL;
                }
        }
        if (fsg->intreq) {
                usb_ep_free_request(fsg->intr_in, fsg->intreq);
                fsg->intreq = NULL;
        }

        /* Disable the endpoints */
        if (fsg->bulk_in_enabled) {
                usb_ep_disable(fsg->bulk_in);
                fsg->bulk_in_enabled = 0;
        }
        if (fsg->bulk_out_enabled) {
                usb_ep_disable(fsg->bulk_out);
                fsg->bulk_out_enabled = 0;
        }
        if (fsg->intr_in_enabled) {
                usb_ep_disable(fsg->intr_in);
                fsg->intr_in_enabled = 0;
        }

        fsg->running = 0;
        if (altsetting < 0 || rc != 0)
                return rc;

        DBG(fsg, "set interface %d\n", altsetting);

        /* Enable the endpoints */
        d = ep_desc(fsg->gadget, &fs_bulk_in_desc, &hs_bulk_in_desc);
        if ((rc = enable_endpoint(fsg, fsg->bulk_in, d)) != 0)
                goto reset;
        fsg->bulk_in_enabled = 1;

        d = ep_desc(fsg->gadget, &fs_bulk_out_desc, &hs_bulk_out_desc);
        if ((rc = enable_endpoint(fsg, fsg->bulk_out, d)) != 0)
                goto reset;
        fsg->bulk_out_enabled = 1;
        fsg->bulk_out_maxpacket = le16_to_cpu(d->wMaxPacketSize);

        if (transport_is_cbi()) {
                d = ep_desc(fsg->gadget, &fs_intr_in_desc, &hs_intr_in_desc);
                if ((rc = enable_endpoint(fsg, fsg->intr_in, d)) != 0)
                        goto reset;
                fsg->intr_in_enabled = 1;
        }

        /* Allocate the requests */
        for (i = 0; i < NUM_BUFFERS; ++i) {
                struct fsg_buffhd       *bh = &fsg->buffhds[i];

                if ((rc = alloc_request(fsg, fsg->bulk_in, &bh->inreq)) != 0)
                        goto reset;
                if ((rc = alloc_request(fsg, fsg->bulk_out, &bh->outreq)) != 0)
                        goto reset;
                bh->inreq->buf = bh->outreq->buf = bh->buf;
                bh->inreq->context = bh->outreq->context = bh;
                bh->inreq->complete = bulk_in_complete;
                bh->outreq->complete = bulk_out_complete;
        }
        if (transport_is_cbi()) {
                if ((rc = alloc_request(fsg, fsg->intr_in, &fsg->intreq)) != 0)
                        goto reset;
                fsg->intreq->complete = intr_in_complete;
        }

        fsg->running = 1;
        for (i = 0; i < fsg->nluns; ++i)
                fsg->luns[i].unit_attention_data = SS_RESET_OCCURRED;
        return rc;
}


/*
 * Change our operational configuration.  This code must agree with the code
 * that returns config descriptors, and with interface altsetting code.
 *
 * It's also responsible for power management interactions.  Some
 * configurations might not work with our current power sources.
 * For now we just assume the gadget is always self-powered.
 */
static int do_set_config(struct fsg_dev *fsg, u8 new_config)
{
        int     rc = 0;

        /* Disable the single interface */
        if (fsg->config != 0) {
                DBG(fsg, "reset config\n");
                fsg->config = 0;
                rc = do_set_interface(fsg, -1);
        }

        /* Enable the interface */
        if (new_config != 0) {
                fsg->config = new_config;
                if ((rc = do_set_interface(fsg, 0)) != 0)
                        fsg->config = 0;        // Reset on errors
                else {
                        char *speed;

                        switch (fsg->gadget->speed) {
                        case USB_SPEED_LOW:     speed = "low";  break;
                        case USB_SPEED_FULL:    speed = "full"; break;
                        case USB_SPEED_HIGH:    speed = "high"; break;
                        default:                speed = "?";    break;
                        }
                        INFO(fsg, "%s speed config #%d\n", speed, fsg->config);
                }
        }
        return rc;
}


/*-------------------------------------------------------------------------*/

static void handle_exception(struct fsg_dev *fsg)
{
        siginfo_t               info;
        int                     sig;
        int                     i;
        int                     num_active;
        struct fsg_buffhd       *bh;
        enum fsg_state          old_state;
        u8                      new_config;
        struct lun              *curlun;
        unsigned int            exception_req_tag;
        int                     rc;

        /* Clear the existing signals.  Anything but SIGUSR1 is converted
         * into a high-priority EXIT exception. */
        for (;;) {
                sig = dequeue_signal_lock(current, &current->blocked, &info);
                if (!sig)
                        break;
                if (sig != SIGUSR1) {
                        if (fsg->state < FSG_STATE_EXIT)
                                DBG(fsg, "Main thread exiting on signal\n");
                        raise_exception(fsg, FSG_STATE_EXIT);
                }
        }

        /* Cancel all the pending transfers */
        if (fsg->intreq_busy)
                usb_ep_dequeue(fsg->intr_in, fsg->intreq);
        for (i = 0; i < NUM_BUFFERS; ++i) {
                bh = &fsg->buffhds[i];
                if (bh->inreq_busy)
                        usb_ep_dequeue(fsg->bulk_in, bh->inreq);
                if (bh->outreq_busy)
                        usb_ep_dequeue(fsg->bulk_out, bh->outreq);
        }

        /* Wait until everything is idle */
        for (;;) {
                num_active = fsg->intreq_busy;
                for (i = 0; i < NUM_BUFFERS; ++i) {
                        bh = &fsg->buffhds[i];
                        num_active += bh->inreq_busy + bh->outreq_busy;
                }
                if (num_active == 0)
                        break;
                if (sleep_thread(fsg))
                        return;
        }

        /* Clear out the controller's fifos */
        if (fsg->bulk_in_enabled)
                usb_ep_fifo_flush(fsg->bulk_in);
        if (fsg->bulk_out_enabled)
                usb_ep_fifo_flush(fsg->bulk_out);
        if (fsg->intr_in_enabled)
                usb_ep_fifo_flush(fsg->intr_in);

        /* Reset the I/O buffer states and pointers, the SCSI
         * state, and the exception.  Then invoke the handler. */
        spin_lock_irq(&fsg->lock);

        for (i = 0; i < NUM_BUFFERS; ++i) {
                bh = &fsg->buffhds[i];
                bh->state = BUF_STATE_EMPTY;
        }
        fsg->next_buffhd_to_fill = fsg->next_buffhd_to_drain =
                        &fsg->buffhds[0];

        exception_req_tag = fsg->exception_req_tag;
        new_config = fsg->new_config;
        old_state = fsg->state;

        if (old_state == FSG_STATE_ABORT_BULK_OUT)
                fsg->state = FSG_STATE_STATUS_PHASE;
        else {
                for (i = 0; i < fsg->nluns; ++i) {
                        curlun = &fsg->luns[i];
                        curlun->prevent_medium_removal = 0;
                        curlun->sense_data = curlun->unit_attention_data =
                                        SS_NO_SENSE;
                        curlun->sense_data_info = 0;
                        curlun->info_valid = 0;
                }
                fsg->state = FSG_STATE_IDLE;
        }
        spin_unlock_irq(&fsg->lock);

        /* Carry out any extra actions required for the exception */
        switch (old_state) {
        default:
                break;

        case FSG_STATE_ABORT_BULK_OUT:
                send_status(fsg);
                spin_lock_irq(&fsg->lock);
                if (fsg->state == FSG_STATE_STATUS_PHASE)
                        fsg->state = FSG_STATE_IDLE;
                spin_unlock_irq(&fsg->lock);
                break;

        case FSG_STATE_RESET:
                /* In case we were forced against our will to halt a
                 * bulk endpoint, clear the halt now.  (The SuperH UDC
                 * requires this.) */
                if (test_and_clear_bit(CLEAR_BULK_HALTS,
                                &fsg->atomic_bitflags)) {
                        usb_ep_clear_halt(fsg->bulk_in);
                        usb_ep_clear_halt(fsg->bulk_out);
                }

                if (transport_is_bbb()) {
                        if (fsg->ep0_req_tag == exception_req_tag)
                                ep0_queue(fsg); // Complete the status stage

                } else if (transport_is_cbi())
                        send_status(fsg);       // Status by interrupt pipe

                /* Technically this should go here, but it would only be
                 * a waste of time.  Ditto for the INTERFACE_CHANGE and
                 * CONFIG_CHANGE cases. */
                // for (i = 0; i < fsg->nluns; ++i)
                //      fsg->luns[i].unit_attention_data = SS_RESET_OCCURRED;
                break;

        case FSG_STATE_INTERFACE_CHANGE:
                rc = do_set_interface(fsg, 0);
                if (fsg->ep0_req_tag != exception_req_tag)
                        break;
                if (rc != 0)                    // STALL on errors
                        fsg_set_halt(fsg, fsg->ep0);
                else                            // Complete the status stage
                        ep0_queue(fsg);
                break;

        case FSG_STATE_CONFIG_CHANGE:
                rc = do_set_config(fsg, new_config);
                if (fsg->ep0_req_tag != exception_req_tag)
                        break;
                if (rc != 0)                    // STALL on errors
                        fsg_set_halt(fsg, fsg->ep0);
                else                            // Complete the status stage
                        ep0_queue(fsg);
                break;

        case FSG_STATE_DISCONNECT:
                fsync_all(fsg);
                do_set_config(fsg, 0);          // Unconfigured state
                break;

        case FSG_STATE_EXIT:
        case FSG_STATE_TERMINATED:
                do_set_config(fsg, 0);                  // Free resources
                spin_lock_irq(&fsg->lock);
                fsg->state = FSG_STATE_TERMINATED;      // Stop the thread
                spin_unlock_irq(&fsg->lock);
                break;
        }
}


/*-------------------------------------------------------------------------*/

static int fsg_main_thread(void *fsg_)
{
        struct fsg_dev          *fsg = fsg_;

        /* Allow the thread to be killed by a signal, but set the signal mask
         * to block everything but INT, TERM, KILL, and USR1. */
        allow_signal(SIGINT);
        allow_signal(SIGTERM);
        allow_signal(SIGKILL);
        allow_signal(SIGUSR1);

        /* Allow the thread to be frozen */
        set_freezable();

        /* Arrange for userspace references to be interpreted as kernel
         * pointers.  That way we can pass a kernel pointer to a routine
         * that expects a __user pointer and it will work okay. */
        set_fs(get_ds());

        /* The main loop */
        while (fsg->state != FSG_STATE_TERMINATED) {
                if (exception_in_progress(fsg) || signal_pending(current)) {
                        handle_exception(fsg);
                        continue;
                }

                if (!fsg->running) {
                        sleep_thread(fsg);
                        continue;
                }

                if (get_next_command(fsg))
                        continue;

                spin_lock_irq(&fsg->lock);
                if (!exception_in_progress(fsg))
                        fsg->state = FSG_STATE_DATA_PHASE;
                spin_unlock_irq(&fsg->lock);

                if (do_scsi_command(fsg) || finish_reply(fsg))
                        continue;

                spin_lock_irq(&fsg->lock);
                if (!exception_in_progress(fsg))
                        fsg->state = FSG_STATE_STATUS_PHASE;
                spin_unlock_irq(&fsg->lock);

                if (send_status(fsg))
                        continue;

                spin_lock_irq(&fsg->lock);
                if (!exception_in_progress(fsg))
                        fsg->state = FSG_STATE_IDLE;
                spin_unlock_irq(&fsg->lock);
                }

        spin_lock_irq(&fsg->lock);
        fsg->thread_task = NULL;
        spin_unlock_irq(&fsg->lock);

        /* In case we are exiting because of a signal, unregister the
         * gadget driver and close the backing file. */
        if (test_and_clear_bit(REGISTERED, &fsg->atomic_bitflags)) {
                usb_gadget_unregister_driver(&fsg_driver);
                close_all_backing_files(fsg);
        }

        /* Let the unbind and cleanup routines know the thread has exited */
        complete_and_exit(&fsg->thread_notifier, 0);
}


/*-------------------------------------------------------------------------*/

/* If the next two routines are called while the gadget is registered,
 * the caller must own fsg->filesem for writing. */

static int open_backing_file(struct lun *curlun, const char *filename)
{
        int                             ro;
        struct file                     *filp = NULL;
        int                             rc = -EINVAL;
        struct inode                    *inode = NULL;
        loff_t                          size;
        loff_t                          num_sectors;

        /* R/W if we can, R/O if we must */
        ro = curlun->ro;
        if (!ro) {
                filp = filp_open(filename, O_RDWR | O_LARGEFILE, 0);
                if (-EROFS == PTR_ERR(filp))
                        ro = 1;
        }
        if (ro)
                filp = filp_open(filename, O_RDONLY | O_LARGEFILE, 0);
        if (IS_ERR(filp)) {
                LINFO(curlun, "unable to open backing file: %s\n", filename);
                return PTR_ERR(filp);
        }

        if (!(filp->f_mode & FMODE_WRITE))
                ro = 1;

        if (filp->f_path.dentry)
                inode = filp->f_path.dentry->d_inode;
        if (inode && S_ISBLK(inode->i_mode)) {
                if (bdev_read_only(inode->i_bdev))
                        ro = 1;
        } else if (!inode || !S_ISREG(inode->i_mode)) {
                LINFO(curlun, "invalid file type: %s\n", filename);
                goto out;
        }

        /* If we can't read the file, it's no good.
         * If we can't write the file, use it read-only. */
        if (!filp->f_op || !(filp->f_op->read || filp->f_op->aio_read)) {
                LINFO(curlun, "file not readable: %s\n", filename);
                goto out;
        }
        if (!(filp->f_op->write || filp->f_op->aio_write))
                ro = 1;

        size = i_size_read(inode->i_mapping->host);
        if (size < 0) {
                LINFO(curlun, "unable to find file size: %s\n", filename);
                rc = (int) size;
                goto out;
        }
        num_sectors = size >> 9;        // File size in 512-byte sectors
        if (num_sectors == 0) {
                LINFO(curlun, "file too small: %s\n", filename);
                rc = -ETOOSMALL;
                goto out;
        }

        get_file(filp);
        curlun->ro = ro;
        curlun->filp = filp;
        curlun->file_length = size;
        curlun->num_sectors = num_sectors;
        LDBG(curlun, "open backing file: %s\n", filename);
        rc = 0;

out:
        filp_close(filp, current->files);
        return rc;
}


static void close_backing_file(struct lun *curlun)
{
        if (curlun->filp) {
                LDBG(curlun, "close backing file\n");
                fput(curlun->filp);
                curlun->filp = NULL;
        }
}

static void close_all_backing_files(struct fsg_dev *fsg)
{
        int     i;

        for (i = 0; i < fsg->nluns; ++i)
                close_backing_file(&fsg->luns[i]);
}


static ssize_t show_ro(struct device *dev, struct device_attribute *attr, char *buf)
{
        struct lun      *curlun = dev_to_lun(dev);

        return sprintf(buf, "%d\n", curlun->ro);
}

static ssize_t show_file(struct device *dev, struct device_attribute *attr,
                char *buf)
{
        struct lun      *curlun = dev_to_lun(dev);
        struct fsg_dev  *fsg = dev_get_drvdata(dev);
        char            *p;
        ssize_t         rc;

        down_read(&fsg->filesem);
        if (backing_file_is_open(curlun)) {     // Get the complete pathname
                p = d_path(&curlun->filp->f_path, buf, PAGE_SIZE - 1);
                if (IS_ERR(p))
                        rc = PTR_ERR(p);
                else {
                        rc = strlen(p);
                        memmove(buf, p, rc);
                        buf[rc] = '\n';         // Add a newline
                        buf[++rc] = 0;
                }
        } else {                                // No file, return 0 bytes
                *buf = 0;
                rc = 0;
        }
        up_read(&fsg->filesem);
        return rc;
}


static ssize_t store_ro(struct device *dev, struct device_attribute *attr,
                const char *buf, size_t count)
{
        ssize_t         rc = count;
        struct lun      *curlun = dev_to_lun(dev);
        struct fsg_dev  *fsg = dev_get_drvdata(dev);
        int             i;

        if (sscanf(buf, "%d", &i) != 1)
                return -EINVAL;

        /* Allow the write-enable status to change only while the backing file
         * is closed. */
        down_read(&fsg->filesem);
        if (backing_file_is_open(curlun)) {
                LDBG(curlun, "read-only status change prevented\n");
                rc = -EBUSY;
        } else {
                curlun->ro = !!i;
                LDBG(curlun, "read-only status set to %d\n", curlun->ro);
        }
        up_read(&fsg->filesem);
        return rc;
}

static ssize_t store_file(struct device *dev, struct device_attribute *attr,
                const char *buf, size_t count)
{
        struct lun      *curlun = dev_to_lun(dev);
        struct fsg_dev  *fsg = dev_get_drvdata(dev);
        int             rc = 0;

        if (curlun->prevent_medium_removal && backing_file_is_open(curlun)) {
                LDBG(curlun, "eject attempt prevented\n");
                return -EBUSY;                          // "Door is locked"
        }

        /* Remove a trailing newline */
        if (count > 0 && buf[count-1] == '\n')
                ((char *) buf)[count-1] = 0;            // Ugh!

        /* Eject current medium */
        down_write(&fsg->filesem);
        if (backing_file_is_open(curlun)) {
                close_backing_file(curlun);
                curlun->unit_attention_data = SS_MEDIUM_NOT_PRESENT;
        }

        /* Load new medium */
        if (count > 0 && buf[0]) {
                rc = open_backing_file(curlun, buf);
                if (rc == 0)
                        curlun->unit_attention_data =
                                        SS_NOT_READY_TO_READY_TRANSITION;
        }
        up_write(&fsg->filesem);
        return (rc < 0 ? rc : count);
}


/* The write permissions and store_xxx pointers are set in fsg_bind() */
static DEVICE_ATTR(ro, 0444, show_ro, NULL);
static DEVICE_ATTR(file, 0444, show_file, NULL);


/*-------------------------------------------------------------------------*/

static void fsg_release(struct kref *ref)
{
        struct fsg_dev  *fsg = container_of(ref, struct fsg_dev, ref);

        kfree(fsg->luns);
        kfree(fsg);
}

static void lun_release(struct device *dev)
{
        struct fsg_dev  *fsg = dev_get_drvdata(dev);

        kref_put(&fsg->ref, fsg_release);
}

static void /* __init_or_exit */ fsg_unbind(struct usb_gadget *gadget)
{
        struct fsg_dev          *fsg = get_gadget_data(gadget);
        int                     i;
        struct lun              *curlun;
        struct usb_request      *req = fsg->ep0req;

        DBG(fsg, "unbind\n");
        clear_bit(REGISTERED, &fsg->atomic_bitflags);

        /* Unregister the sysfs attribute files and the LUNs */
        for (i = 0; i < fsg->nluns; ++i) {
                curlun = &fsg->luns[i];
                if (curlun->registered) {
                        device_remove_file(&curlun->dev, &dev_attr_ro);
                        device_remove_file(&curlun->dev, &dev_attr_file);
                        device_unregister(&curlun->dev);
                        curlun->registered = 0;
                }
        }

        /* If the thread isn't already dead, tell it to exit now */
        if (fsg->state != FSG_STATE_TERMINATED) {
                raise_exception(fsg, FSG_STATE_EXIT);
                wait_for_completion(&fsg->thread_notifier);

                /* The cleanup routine waits for this completion also */
                complete(&fsg->thread_notifier);
        }

        /* Free the data buffers */
        for (i = 0; i < NUM_BUFFERS; ++i)
                kfree(fsg->buffhds[i].buf);

        /* Free the request and buffer for endpoint 0 */
        if (req) {
                kfree(req->buf);
                usb_ep_free_request(fsg->ep0, req);
        }

        set_gadget_data(gadget, NULL);
}


static int __init check_parameters(struct fsg_dev *fsg)
{
        int     prot;
        int     gcnum;

        /* Store the default values */
        mod_data.transport_type = USB_PR_BULK;
        mod_data.transport_name = "Bulk-only";
        mod_data.protocol_type = USB_SC_SCSI;
        mod_data.protocol_name = "Transparent SCSI";

        if (gadget_is_sh(fsg->gadget))
                mod_data.can_stall = 0;

        if (mod_data.release == 0xffff) {       // Parameter wasn't set
                /* The sa1100 controller is not supported */
                if (gadget_is_sa1100(fsg->gadget))
                        gcnum = -1;
                else
                        gcnum = usb_gadget_controller_number(fsg->gadget);
                if (gcnum >= 0)
                        mod_data.release = 0x0300 + gcnum;
                else {
                        WARN(fsg, "controller '%s' not recognized\n",
                                fsg->gadget->name);
                        mod_data.release = 0x0399;
                }
        }

        prot = simple_strtol(mod_data.protocol_parm, NULL, 0);

#ifdef CONFIG_USB_FILE_STORAGE_TEST
        if (strnicmp(mod_data.transport_parm, "BBB", 10) == 0) {
                ;               // Use default setting
        } else if (strnicmp(mod_data.transport_parm, "CB", 10) == 0) {
                mod_data.transport_type = USB_PR_CB;
                mod_data.transport_name = "Control-Bulk";
        } else if (strnicmp(mod_data.transport_parm, "CBI", 10) == 0) {
                mod_data.transport_type = USB_PR_CBI;
                mod_data.transport_name = "Control-Bulk-Interrupt";
        } else {
                ERROR(fsg, "invalid transport: %s\n", mod_data.transport_parm);
                return -EINVAL;
        }

        if (strnicmp(mod_data.protocol_parm, "SCSI", 10) == 0 ||
                        prot == USB_SC_SCSI) {
                ;               // Use default setting
        } else if (strnicmp(mod_data.protocol_parm, "RBC", 10) == 0 ||
                        prot == USB_SC_RBC) {
                mod_data.protocol_type = USB_SC_RBC;
                mod_data.protocol_name = "RBC";
        } else if (strnicmp(mod_data.protocol_parm, "8020", 4) == 0 ||
                        strnicmp(mod_data.protocol_parm, "ATAPI", 10) == 0 ||
                        prot == USB_SC_8020) {
                mod_data.protocol_type = USB_SC_8020;
                mod_data.protocol_name = "8020i (ATAPI)";
        } else if (strnicmp(mod_data.protocol_parm, "QIC", 3) == 0 ||
                        prot == USB_SC_QIC) {
                mod_data.protocol_type = USB_SC_QIC;
                mod_data.protocol_name = "QIC-157";
        } else if (strnicmp(mod_data.protocol_parm, "UFI", 10) == 0 ||
                        prot == USB_SC_UFI) {
                mod_data.protocol_type = USB_SC_UFI;
                mod_data.protocol_name = "UFI";
        } else if (strnicmp(mod_data.protocol_parm, "8070", 4) == 0 ||
                        prot == USB_SC_8070) {
                mod_data.protocol_type = USB_SC_8070;
                mod_data.protocol_name = "8070i";
        } else {
                ERROR(fsg, "invalid protocol: %s\n", mod_data.protocol_parm);
                return -EINVAL;
        }

        mod_data.buflen &= PAGE_CACHE_MASK;
        if (mod_data.buflen <= 0) {
                ERROR(fsg, "invalid buflen\n");
                return -ETOOSMALL;
        }
#endif /* CONFIG_USB_FILE_STORAGE_TEST */

        return 0;
}


static int __init fsg_bind(struct usb_gadget *gadget)
{
        struct fsg_dev          *fsg = the_fsg;
        int                     rc;
        int                     i;
        struct lun              *curlun;
        struct usb_ep           *ep;
        struct usb_request      *req;
        char                    *pathbuf, *p;

        fsg->gadget = gadget;
        set_gadget_data(gadget, fsg);
        fsg->ep0 = gadget->ep0;
        fsg->ep0->driver_data = fsg;

        if ((rc = check_parameters(fsg)) != 0)
                goto out;

        if (mod_data.removable) {       // Enable the store_xxx attributes
                dev_attr_ro.attr.mode = dev_attr_file.attr.mode = 0644;
                dev_attr_ro.store = store_ro;
                dev_attr_file.store = store_file;
        }

        /* Find out how many LUNs there should be */
        i = mod_data.nluns;
        if (i == 0)
                i = max(mod_data.num_filenames, 1u);
        if (i > MAX_LUNS) {
                ERROR(fsg, "invalid number of LUNs: %d\n", i);
                rc = -EINVAL;
                goto out;
        }

        /* Create the LUNs, open their backing files, and register the
         * LUN devices in sysfs. */
        fsg->luns = kzalloc(i * sizeof(struct lun), GFP_KERNEL);
        if (!fsg->luns) {
                rc = -ENOMEM;
                goto out;
        }
        fsg->nluns = i;

        for (i = 0; i < fsg->nluns; ++i) {
                curlun = &fsg->luns[i];
                curlun->ro = mod_data.ro[i];
                curlun->dev.release = lun_release;
                curlun->dev.parent = &gadget->dev;
                curlun->dev.driver = &fsg_driver.driver;
                dev_set_drvdata(&curlun->dev, fsg);
                snprintf(curlun->dev.bus_id, BUS_ID_SIZE,
                                "%s-lun%d", gadget->dev.bus_id, i);

                if ((rc = device_register(&curlun->dev)) != 0) {
                        INFO(fsg, "failed to register LUN%d: %d\n", i, rc);
                        goto out;
                }
                if ((rc = device_create_file(&curlun->dev,
                                        &dev_attr_ro)) != 0 ||
                                (rc = device_create_file(&curlun->dev,
                                        &dev_attr_file)) != 0) {
                        device_unregister(&curlun->dev);
                        goto out;
                }
                curlun->registered = 1;
                kref_get(&fsg->ref);

                if (mod_data.file[i] && *mod_data.file[i]) {
                        if ((rc = open_backing_file(curlun,
                                        mod_data.file[i])) != 0)
                                goto out;
                } else if (!mod_data.removable) {
                        ERROR(fsg, "no file given for LUN%d\n", i);
                        rc = -EINVAL;
                        goto out;
                }
        }

        /* Find all the endpoints we will use */
        usb_ep_autoconfig_reset(gadget);
        ep = usb_ep_autoconfig(gadget, &fs_bulk_in_desc);
        if (!ep)
                goto autoconf_fail;
        ep->driver_data = fsg;          // claim the endpoint
        fsg->bulk_in = ep;

        ep = usb_ep_autoconfig(gadget, &fs_bulk_out_desc);
        if (!ep)
                goto autoconf_fail;
        ep->driver_data = fsg;          // claim the endpoint
        fsg->bulk_out = ep;

        if (transport_is_cbi()) {
                ep = usb_ep_autoconfig(gadget, &fs_intr_in_desc);
                if (!ep)
                        goto autoconf_fail;
                ep->driver_data = fsg;          // claim the endpoint
                fsg->intr_in = ep;
        }

        /* Fix up the descriptors */
        device_desc.bMaxPacketSize0 = fsg->ep0->maxpacket;
        device_desc.idVendor = cpu_to_le16(mod_data.vendor);
        device_desc.idProduct = cpu_to_le16(mod_data.product);
        device_desc.bcdDevice = cpu_to_le16(mod_data.release);

        i = (transport_is_cbi() ? 3 : 2);       // Number of endpoints
        intf_desc.bNumEndpoints = i;
        intf_desc.bInterfaceSubClass = mod_data.protocol_type;
        intf_desc.bInterfaceProtocol = mod_data.transport_type;
        fs_function[i + FS_FUNCTION_PRE_EP_ENTRIES] = NULL;

        if (gadget_is_dualspeed(gadget)) {
                hs_function[i + HS_FUNCTION_PRE_EP_ENTRIES] = NULL;

                /* Assume ep0 uses the same maxpacket value for both speeds */
                dev_qualifier.bMaxPacketSize0 = fsg->ep0->maxpacket;

                /* Assume endpoint addresses are the same for both speeds */
                hs_bulk_in_desc.bEndpointAddress =
                                fs_bulk_in_desc.bEndpointAddress;
                hs_bulk_out_desc.bEndpointAddress =
                                fs_bulk_out_desc.bEndpointAddress;
                hs_intr_in_desc.bEndpointAddress =
                                fs_intr_in_desc.bEndpointAddress;
        }

        if (gadget_is_otg(gadget))
                otg_desc.bmAttributes |= USB_OTG_HNP;

        rc = -ENOMEM;

        /* Allocate the request and buffer for endpoint 0 */
        fsg->ep0req = req = usb_ep_alloc_request(fsg->ep0, GFP_KERNEL);
        if (!req)
                goto out;
        req->buf = kmalloc(EP0_BUFSIZE, GFP_KERNEL);
        if (!req->buf)
                goto out;
        req->complete = ep0_complete;

        /* Allocate the data buffers */
        for (i = 0; i < NUM_BUFFERS; ++i) {
                struct fsg_buffhd       *bh = &fsg->buffhds[i];

                /* Allocate for the bulk-in endpoint.  We assume that
                 * the buffer will also work with the bulk-out (and
                 * interrupt-in) endpoint. */
                bh->buf = kmalloc(mod_data.buflen, GFP_KERNEL);
                if (!bh->buf)
                        goto out;
                bh->next = bh + 1;
        }
        fsg->buffhds[NUM_BUFFERS - 1].next = &fsg->buffhds[0];

        /* This should reflect the actual gadget power source */
        usb_gadget_set_selfpowered(gadget);

        snprintf(manufacturer, sizeof manufacturer, "%s %s with %s",
                        init_utsname()->sysname, init_utsname()->release,
                        gadget->name);

        /* On a real device, serial[] would be loaded from permanent
         * storage.  We just encode it from the driver version string. */
        for (i = 0; i < sizeof(serial) - 2; i += 2) {
                unsigned char           c = DRIVER_VERSION[i / 2];

                if (!c)
                        break;
                sprintf(&serial[i], "%02X", c);
        }

        fsg->thread_task = kthread_create(fsg_main_thread, fsg,
                        "file-storage-gadget");
        if (IS_ERR(fsg->thread_task)) {
                rc = PTR_ERR(fsg->thread_task);
                goto out;
        }

        INFO(fsg, DRIVER_DESC ", version: " DRIVER_VERSION "\n");
        INFO(fsg, "Number of LUNs=%d\n", fsg->nluns);

        pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
        for (i = 0; i < fsg->nluns; ++i) {
                curlun = &fsg->luns[i];
                if (backing_file_is_open(curlun)) {
                        p = NULL;
                        if (pathbuf) {
                                p = d_path(&curlun->filp->f_path,
                                           pathbuf, PATH_MAX);
                                if (IS_ERR(p))
                                        p = NULL;
                        }
                        LINFO(curlun, "ro=%d, file: %s\n",
                                        curlun->ro, (p ? p : "(error)"));
                }
        }
        kfree(pathbuf);

        DBG(fsg, "transport=%s (x%02x)\n",
                        mod_data.transport_name, mod_data.transport_type);
        DBG(fsg, "protocol=%s (x%02x)\n",
                        mod_data.protocol_name, mod_data.protocol_type);
        DBG(fsg, "VendorID=x%04x, ProductID=x%04x, Release=x%04x\n",
                        mod_data.vendor, mod_data.product, mod_data.release);
        DBG(fsg, "removable=%d, stall=%d, buflen=%u\n",
                        mod_data.removable, mod_data.can_stall,
                        mod_data.buflen);
        DBG(fsg, "I/O thread pid: %d\n", task_pid_nr(fsg->thread_task));

        set_bit(REGISTERED, &fsg->atomic_bitflags);

        /* Tell the thread to start working */
        wake_up_process(fsg->thread_task);
        return 0;

autoconf_fail:
        ERROR(fsg, "unable to autoconfigure all endpoints\n");
        rc = -ENOTSUPP;

out:
        fsg->state = FSG_STATE_TERMINATED;      // The thread is dead
        fsg_unbind(gadget);
        close_all_backing_files(fsg);
        return rc;
}


/*-------------------------------------------------------------------------*/

static void fsg_suspend(struct usb_gadget *gadget)
{
        struct fsg_dev          *fsg = get_gadget_data(gadget);

        DBG(fsg, "suspend\n");
        set_bit(SUSPENDED, &fsg->atomic_bitflags);
}

static void fsg_resume(struct usb_gadget *gadget)
{
        struct fsg_dev          *fsg = get_gadget_data(gadget);

        DBG(fsg, "resume\n");
        clear_bit(SUSPENDED, &fsg->atomic_bitflags);
}


/*-------------------------------------------------------------------------*/

static struct usb_gadget_driver         fsg_driver = {
#ifdef CONFIG_USB_GADGET_DUALSPEED
        .speed          = USB_SPEED_HIGH,
#else
        .speed          = USB_SPEED_FULL,
#endif
        .function       = (char *) longname,
        .bind           = fsg_bind,
        .unbind         = fsg_unbind,
        .disconnect     = fsg_disconnect,
        .setup          = fsg_setup,
        .suspend        = fsg_suspend,
        .resume         = fsg_resume,

        .driver         = {
                .name           = (char *) shortname,
                .owner          = THIS_MODULE,
                // .release = ...
                // .suspend = ...
                // .resume = ...
        },
};


static int __init fsg_alloc(void)
{
        struct fsg_dev          *fsg;

        fsg = kzalloc(sizeof *fsg, GFP_KERNEL);
        if (!fsg)
                return -ENOMEM;
        spin_lock_init(&fsg->lock);
        init_rwsem(&fsg->filesem);
        kref_init(&fsg->ref);
        init_completion(&fsg->thread_notifier);

        the_fsg = fsg;
        return 0;
}


static int __init fsg_init(void)
{
        int             rc;
        struct fsg_dev  *fsg;

        if ((rc = fsg_alloc()) != 0)
                return rc;
        fsg = the_fsg;
        if ((rc = usb_gadget_register_driver(&fsg_driver)) != 0)
                kref_put(&fsg->ref, fsg_release);
        return rc;
}
module_init(fsg_init);


static void __exit fsg_cleanup(void)
{
        struct fsg_dev  *fsg = the_fsg;

        /* Unregister the driver iff the thread hasn't already done so */
        if (test_and_clear_bit(REGISTERED, &fsg->atomic_bitflags))
                usb_gadget_unregister_driver(&fsg_driver);

        /* Wait for the thread to finish up */
        wait_for_completion(&fsg->thread_notifier);

        close_all_backing_files(fsg);
        kref_put(&fsg->ref, fsg_release);
}
module_exit(fsg_cleanup);