[SCSI] IBM VSCSI Client: sending client info to server

[linux-2.6] / drivers / scsi / ibmvscsi / ibmvscsi.c

/* ------------------------------------------------------------
 * ibmvscsi.c
 * (C) Copyright IBM Corporation 1994, 2004
 * Authors: Colin DeVilbiss (devilbis@us.ibm.com)
 *          Santiago Leon (santil@us.ibm.com)
 *          Dave Boutcher (sleddog@us.ibm.com)
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
 * USA
 *
 * ------------------------------------------------------------
 * Emulation of a SCSI host adapter for Virtual I/O devices
 *
 * This driver supports the SCSI adapter implemented by the IBM
 * Power5 firmware.  That SCSI adapter is not a physical adapter,
 * but allows Linux SCSI peripheral drivers to directly
 * access devices in another logical partition on the physical system.
 *
 * The virtual adapter(s) are present in the open firmware device
 * tree just like real adapters.
 *
 * One of the capabilities provided on these systems is the ability
 * to DMA between partitions.  The architecture states that for VSCSI,
 * the server side is allowed to DMA to and from the client.  The client
 * is never trusted to DMA to or from the server directly.
 *
 * Messages are sent between partitions on a "Command/Response Queue" 
 * (CRQ), which is just a buffer of 16 byte entries in the receiver's 
 * Senders cannot access the buffer directly, but send messages by
 * making a hypervisor call and passing in the 16 bytes.  The hypervisor
 * puts the message in the next 16 byte space in round-robbin fashion,
 * turns on the high order bit of the message (the valid bit), and 
 * generates an interrupt to the receiver (if interrupts are turned on.) 
 * The receiver just turns off the valid bit when they have copied out
 * the message.
 *
 * The VSCSI client builds a SCSI Remote Protocol (SRP) Information Unit
 * (IU) (as defined in the T10 standard available at www.t10.org), gets 
 * a DMA address for the message, and sends it to the server as the
 * payload of a CRQ message.  The server DMAs the SRP IU and processes it,
 * including doing any additional data transfers.  When it is done, it
 * DMAs the SRP response back to the same address as the request came from,
 * and sends a CRQ message back to inform the client that the request has
 * completed.
 *
 * Note that some of the underlying infrastructure is different between
 * machines conforming to the "RS/6000 Platform Architecture" (RPA) and
 * the older iSeries hypervisor models.  To support both, some low level
 * routines have been broken out into rpa_vscsi.c and iseries_vscsi.c.
 * The Makefile should pick one, not two, not zero, of these.
 *
 * TODO: This is currently pretty tied to the IBM i/pSeries hypervisor
 * interfaces.  It would be really nice to abstract this above an RDMA
 * layer.
 */

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/dma-mapping.h>
#include <linux/delay.h>
#include <asm/vio.h>
#include <scsi/scsi.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/scsi_host.h>
#include <scsi/scsi_device.h>
#include "ibmvscsi.h"

/* The values below are somewhat arbitrary default values, but 
 * OS/400 will use 3 busses (disks, CDs, tapes, I think.)
 * Note that there are 3 bits of channel value, 6 bits of id, and
 * 5 bits of LUN.
 */
static int max_id = 64;
static int max_channel = 3;
static int init_timeout = 5;
static int max_requests = 50;

#define IBMVSCSI_VERSION "1.5.6"

MODULE_DESCRIPTION("IBM Virtual SCSI");
MODULE_AUTHOR("Dave Boutcher");
MODULE_LICENSE("GPL");
MODULE_VERSION(IBMVSCSI_VERSION);

module_param_named(max_id, max_id, int, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(max_id, "Largest ID value for each channel");
module_param_named(max_channel, max_channel, int, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(max_channel, "Largest channel value");
module_param_named(init_timeout, init_timeout, int, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(init_timeout, "Initialization timeout in seconds");
module_param_named(max_requests, max_requests, int, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(max_requests, "Maximum requests for this adapter");

/* ------------------------------------------------------------
 * Routines for the event pool and event structs
 */
/**
 * initialize_event_pool: - Allocates and initializes the event pool for a host
 * @pool:       event_pool to be initialized
 * @size:       Number of events in pool
 * @hostdata:   ibmvscsi_host_data who owns the event pool
 *
 * Returns zero on success.
*/
static int initialize_event_pool(struct event_pool *pool,
                                 int size, struct ibmvscsi_host_data *hostdata)
{
        int i;

        pool->size = size;
        pool->next = 0;
        pool->events = kmalloc(pool->size * sizeof(*pool->events), GFP_KERNEL);
        if (!pool->events)
                return -ENOMEM;
        memset(pool->events, 0x00, pool->size * sizeof(*pool->events));

        pool->iu_storage =
            dma_alloc_coherent(hostdata->dev,
                               pool->size * sizeof(*pool->iu_storage),
                               &pool->iu_token, 0);
        if (!pool->iu_storage) {
                kfree(pool->events);
                return -ENOMEM;
        }

        for (i = 0; i < pool->size; ++i) {
                struct srp_event_struct *evt = &pool->events[i];
                memset(&evt->crq, 0x00, sizeof(evt->crq));
                atomic_set(&evt->free, 1);
                evt->crq.valid = 0x80;
                evt->crq.IU_length = sizeof(*evt->xfer_iu);
                evt->crq.IU_data_ptr = pool->iu_token + 
                        sizeof(*evt->xfer_iu) * i;
                evt->xfer_iu = pool->iu_storage + i;
                evt->hostdata = hostdata;
        }

        return 0;
}

/**
 * release_event_pool: - Frees memory of an event pool of a host
 * @pool:       event_pool to be released
 * @hostdata:   ibmvscsi_host_data who owns the even pool
 *
 * Returns zero on success.
*/
static void release_event_pool(struct event_pool *pool,
                               struct ibmvscsi_host_data *hostdata)
{
        int i, in_use = 0;
        for (i = 0; i < pool->size; ++i)
                if (atomic_read(&pool->events[i].free) != 1)
                        ++in_use;
        if (in_use)
                printk(KERN_WARNING
                       "ibmvscsi: releasing event pool with %d "
                       "events still in use?\n", in_use);
        kfree(pool->events);
        dma_free_coherent(hostdata->dev,
                          pool->size * sizeof(*pool->iu_storage),
                          pool->iu_storage, pool->iu_token);
}

/**
 * valid_event_struct: - Determines if event is valid.
 * @pool:       event_pool that contains the event
 * @evt:        srp_event_struct to be checked for validity
 *
 * Returns zero if event is invalid, one otherwise.
*/
static int valid_event_struct(struct event_pool *pool,
                                struct srp_event_struct *evt)
{
        int index = evt - pool->events;
        if (index < 0 || index >= pool->size)   /* outside of bounds */
                return 0;
        if (evt != pool->events + index)        /* unaligned */
                return 0;
        return 1;
}

/**
 * ibmvscsi_free-event_struct: - Changes status of event to "free"
 * @pool:       event_pool that contains the event
 * @evt:        srp_event_struct to be modified
 *
*/
static void free_event_struct(struct event_pool *pool,
                                       struct srp_event_struct *evt)
{
        if (!valid_event_struct(pool, evt)) {
                printk(KERN_ERR
                       "ibmvscsi: Freeing invalid event_struct %p "
                       "(not in pool %p)\n", evt, pool->events);
                return;
        }
        if (atomic_inc_return(&evt->free) != 1) {
                printk(KERN_ERR
                       "ibmvscsi: Freeing event_struct %p "
                       "which is not in use!\n", evt);
                return;
        }
}

/**
 * get_evt_struct: - Gets the next free event in pool
 * @pool:       event_pool that contains the events to be searched
 *
 * Returns the next event in "free" state, and NULL if none are free.
 * Note that no synchronization is done here, we assume the host_lock
 * will syncrhonze things.
*/
static struct srp_event_struct *get_event_struct(struct event_pool *pool)
{
        int i;
        int poolsize = pool->size;
        int offset = pool->next;

        for (i = 0; i < poolsize; i++) {
                offset = (offset + 1) % poolsize;
                if (!atomic_dec_if_positive(&pool->events[offset].free)) {
                        pool->next = offset;
                        return &pool->events[offset];
                }
        }

        printk(KERN_ERR "ibmvscsi: found no event struct in pool!\n");
        return NULL;
}

/**
 * init_event_struct: Initialize fields in an event struct that are always 
 *                    required.
 * @evt:        The event
 * @done:       Routine to call when the event is responded to
 * @format:     SRP or MAD format
 * @timeout:    timeout value set in the CRQ
 */
static void init_event_struct(struct srp_event_struct *evt_struct,
                              void (*done) (struct srp_event_struct *),
                              u8 format,
                              int timeout)
{
        evt_struct->cmnd = NULL;
        evt_struct->cmnd_done = NULL;
        evt_struct->sync_srp = NULL;
        evt_struct->crq.format = format;
        evt_struct->crq.timeout = timeout;
        evt_struct->done = done;
}

/* ------------------------------------------------------------
 * Routines for receiving SCSI responses from the hosting partition
 */

/**
 * set_srp_direction: Set the fields in the srp related to data
 *     direction and number of buffers based on the direction in
 *     the scsi_cmnd and the number of buffers
 */
static void set_srp_direction(struct scsi_cmnd *cmd,
                              struct srp_cmd *srp_cmd, 
                              int numbuf)
{
        if (numbuf == 0)
                return;
        
        if (numbuf == 1) {
                if (cmd->sc_data_direction == DMA_TO_DEVICE)
                        srp_cmd->data_out_format = SRP_DIRECT_BUFFER;
                else 
                        srp_cmd->data_in_format = SRP_DIRECT_BUFFER;
        } else {
                if (cmd->sc_data_direction == DMA_TO_DEVICE) {
                        srp_cmd->data_out_format = SRP_INDIRECT_BUFFER;
                        srp_cmd->data_out_count = numbuf;
                } else {
                        srp_cmd->data_in_format = SRP_INDIRECT_BUFFER;
                        srp_cmd->data_in_count = numbuf;
                }
        }
}

/**
 * unmap_cmd_data: - Unmap data pointed in srp_cmd based on the format
 * @cmd:        srp_cmd whose additional_data member will be unmapped
 * @dev:        device for which the memory is mapped
 *
*/
static void unmap_cmd_data(struct srp_cmd *cmd, struct device *dev)
{
        int i;

        if ((cmd->data_out_format == SRP_NO_BUFFER) &&
            (cmd->data_in_format == SRP_NO_BUFFER))
                return;
        else if ((cmd->data_out_format == SRP_DIRECT_BUFFER) ||
                 (cmd->data_in_format == SRP_DIRECT_BUFFER)) {
                struct memory_descriptor *data =
                        (struct memory_descriptor *)cmd->additional_data;
                dma_unmap_single(dev, data->virtual_address, data->length,
                                 DMA_BIDIRECTIONAL);
        } else {
                struct indirect_descriptor *indirect =
                        (struct indirect_descriptor *)cmd->additional_data;
                int num_mapped = indirect->head.length / 
                        sizeof(indirect->list[0]);
                for (i = 0; i < num_mapped; ++i) {
                        struct memory_descriptor *data = &indirect->list[i];
                        dma_unmap_single(dev,
                                         data->virtual_address,
                                         data->length, DMA_BIDIRECTIONAL);
                }
        }
}

/**
 * map_sg_data: - Maps dma for a scatterlist and initializes decriptor fields
 * @cmd:        Scsi_Cmnd with the scatterlist
 * @srp_cmd:    srp_cmd that contains the memory descriptor
 * @dev:        device for which to map dma memory
 *
 * Called by map_data_for_srp_cmd() when building srp cmd from scsi cmd.
 * Returns 1 on success.
*/
static int map_sg_data(struct scsi_cmnd *cmd,
                       struct srp_cmd *srp_cmd, struct device *dev)
{

        int i, sg_mapped;
        u64 total_length = 0;
        struct scatterlist *sg = cmd->request_buffer;
        struct memory_descriptor *data =
            (struct memory_descriptor *)srp_cmd->additional_data;
        struct indirect_descriptor *indirect =
            (struct indirect_descriptor *)data;

        sg_mapped = dma_map_sg(dev, sg, cmd->use_sg, DMA_BIDIRECTIONAL);

        if (sg_mapped == 0)
                return 0;

        set_srp_direction(cmd, srp_cmd, sg_mapped);

        /* special case; we can use a single direct descriptor */
        if (sg_mapped == 1) {
                data->virtual_address = sg_dma_address(&sg[0]);
                data->length = sg_dma_len(&sg[0]);
                data->memory_handle = 0;
                return 1;
        }

        if (sg_mapped > MAX_INDIRECT_BUFS) {
                printk(KERN_ERR
                       "ibmvscsi: More than %d mapped sg entries, got %d\n",
                       MAX_INDIRECT_BUFS, sg_mapped);
                return 0;
        }

        indirect->head.virtual_address = 0;
        indirect->head.length = sg_mapped * sizeof(indirect->list[0]);
        indirect->head.memory_handle = 0;
        for (i = 0; i < sg_mapped; ++i) {
                struct memory_descriptor *descr = &indirect->list[i];
                struct scatterlist *sg_entry = &sg[i];
                descr->virtual_address = sg_dma_address(sg_entry);
                descr->length = sg_dma_len(sg_entry);
                descr->memory_handle = 0;
                total_length += sg_dma_len(sg_entry);
        }
        indirect->total_length = total_length;

        return 1;
}

/**
 * map_single_data: - Maps memory and initializes memory decriptor fields
 * @cmd:        struct scsi_cmnd with the memory to be mapped
 * @srp_cmd:    srp_cmd that contains the memory descriptor
 * @dev:        device for which to map dma memory
 *
 * Called by map_data_for_srp_cmd() when building srp cmd from scsi cmd.
 * Returns 1 on success.
*/
static int map_single_data(struct scsi_cmnd *cmd,
                           struct srp_cmd *srp_cmd, struct device *dev)
{
        struct memory_descriptor *data =
            (struct memory_descriptor *)srp_cmd->additional_data;

        data->virtual_address =
                dma_map_single(dev, cmd->request_buffer,
                               cmd->request_bufflen,
                               DMA_BIDIRECTIONAL);
        if (dma_mapping_error(data->virtual_address)) {
                printk(KERN_ERR
                       "ibmvscsi: Unable to map request_buffer for command!\n");
                return 0;
        }
        data->length = cmd->request_bufflen;
        data->memory_handle = 0;

        set_srp_direction(cmd, srp_cmd, 1);

        return 1;
}

/**
 * map_data_for_srp_cmd: - Calls functions to map data for srp cmds
 * @cmd:        struct scsi_cmnd with the memory to be mapped
 * @srp_cmd:    srp_cmd that contains the memory descriptor
 * @dev:        dma device for which to map dma memory
 *
 * Called by scsi_cmd_to_srp_cmd() when converting scsi cmds to srp cmds 
 * Returns 1 on success.
*/
static int map_data_for_srp_cmd(struct scsi_cmnd *cmd,
                                struct srp_cmd *srp_cmd, struct device *dev)
{
        switch (cmd->sc_data_direction) {
        case DMA_FROM_DEVICE:
        case DMA_TO_DEVICE:
                break;
        case DMA_NONE:
                return 1;
        case DMA_BIDIRECTIONAL:
                printk(KERN_ERR
                       "ibmvscsi: Can't map DMA_BIDIRECTIONAL to read/write\n");
                return 0;
        default:
                printk(KERN_ERR
                       "ibmvscsi: Unknown data direction 0x%02x; can't map!\n",
                       cmd->sc_data_direction);
                return 0;
        }

        if (!cmd->request_buffer)
                return 1;
        if (cmd->use_sg)
                return map_sg_data(cmd, srp_cmd, dev);
        return map_single_data(cmd, srp_cmd, dev);
}

/* ------------------------------------------------------------
 * Routines for sending and receiving SRPs
 */
/**
 * ibmvscsi_send_srp_event: - Transforms event to u64 array and calls send_crq()
 * @evt_struct: evt_struct to be sent
 * @hostdata:   ibmvscsi_host_data of host
 *
 * Returns the value returned from ibmvscsi_send_crq(). (Zero for success)
 * Note that this routine assumes that host_lock is held for synchronization
*/
static int ibmvscsi_send_srp_event(struct srp_event_struct *evt_struct,
                                   struct ibmvscsi_host_data *hostdata)
{
        struct scsi_cmnd *cmnd;
        u64 *crq_as_u64 = (u64 *) &evt_struct->crq;
        int rc;

        /* If we have exhausted our request limit, just fail this request.
         * Note that there are rare cases involving driver generated requests 
         * (such as task management requests) that the mid layer may think we
         * can handle more requests (can_queue) when we actually can't
         */
        if ((evt_struct->crq.format == VIOSRP_SRP_FORMAT) &&
            (atomic_dec_if_positive(&hostdata->request_limit) < 0)) {
                /* See if the adapter is disabled */
                if (atomic_read(&hostdata->request_limit) < 0)
                        goto send_error;
        
                printk(KERN_WARNING 
                       "ibmvscsi: Warning, request_limit exceeded\n");
                unmap_cmd_data(&evt_struct->iu.srp.cmd,
                               hostdata->dev);
                free_event_struct(&hostdata->pool, evt_struct);
                return SCSI_MLQUEUE_HOST_BUSY;
        }

        /* Copy the IU into the transfer area */
        *evt_struct->xfer_iu = evt_struct->iu;
        evt_struct->xfer_iu->srp.generic.tag = (u64)evt_struct;

        /* Add this to the sent list.  We need to do this 
         * before we actually send 
         * in case it comes back REALLY fast
         */
        list_add_tail(&evt_struct->list, &hostdata->sent);

        if ((rc =
             ibmvscsi_send_crq(hostdata, crq_as_u64[0], crq_as_u64[1])) != 0) {
                list_del(&evt_struct->list);

                printk(KERN_ERR "ibmvscsi: failed to send event struct rc %d\n",
                       rc);
                goto send_error;
        }

        return 0;

 send_error:
        unmap_cmd_data(&evt_struct->iu.srp.cmd, hostdata->dev);

        if ((cmnd = evt_struct->cmnd) != NULL) {
                cmnd->result = DID_ERROR << 16;
                evt_struct->cmnd_done(cmnd);
        } else if (evt_struct->done)
                evt_struct->done(evt_struct);
        
        free_event_struct(&hostdata->pool, evt_struct);
        return 0;
}

/**
 * handle_cmd_rsp: -  Handle responses from commands
 * @evt_struct: srp_event_struct to be handled
 *
 * Used as a callback by when sending scsi cmds.
 * Gets called by ibmvscsi_handle_crq()
*/
static void handle_cmd_rsp(struct srp_event_struct *evt_struct)
{
        struct srp_rsp *rsp = &evt_struct->xfer_iu->srp.rsp;
        struct scsi_cmnd *cmnd = evt_struct->cmnd;

        if (unlikely(rsp->type != SRP_RSP_TYPE)) {
                if (printk_ratelimit())
                        printk(KERN_WARNING 
                               "ibmvscsi: bad SRP RSP type %d\n",
                               rsp->type);
        }
        
        if (cmnd) {
                cmnd->result = rsp->status;
                if (((cmnd->result >> 1) & 0x1f) == CHECK_CONDITION)
                        memcpy(cmnd->sense_buffer,
                               rsp->sense_and_response_data,
                               rsp->sense_data_list_length);
                unmap_cmd_data(&evt_struct->iu.srp.cmd, 
                               evt_struct->hostdata->dev);

                if (rsp->doover)
                        cmnd->resid = rsp->data_out_residual_count;
                else if (rsp->diover)
                        cmnd->resid = rsp->data_in_residual_count;
        }

        if (evt_struct->cmnd_done)
                evt_struct->cmnd_done(cmnd);
}

/**
 * lun_from_dev: - Returns the lun of the scsi device
 * @dev:        struct scsi_device
 *
*/
static inline u16 lun_from_dev(struct scsi_device *dev)
{
        return (0x2 << 14) | (dev->id << 8) | (dev->channel << 5) | dev->lun;
}

/**
 * ibmvscsi_queue: - The queuecommand function of the scsi template 
 * @cmd:        struct scsi_cmnd to be executed
 * @done:       Callback function to be called when cmd is completed
*/
static int ibmvscsi_queuecommand(struct scsi_cmnd *cmnd,
                                 void (*done) (struct scsi_cmnd *))
{
        struct srp_cmd *srp_cmd;
        struct srp_event_struct *evt_struct;
        struct ibmvscsi_host_data *hostdata =
                (struct ibmvscsi_host_data *)&cmnd->device->host->hostdata;
        u16 lun = lun_from_dev(cmnd->device);

        evt_struct = get_event_struct(&hostdata->pool);
        if (!evt_struct)
                return SCSI_MLQUEUE_HOST_BUSY;

        init_event_struct(evt_struct,
                          handle_cmd_rsp,
                          VIOSRP_SRP_FORMAT,
                          cmnd->timeout);

        evt_struct->cmnd = cmnd;
        evt_struct->cmnd_done = done;

        /* Set up the actual SRP IU */
        srp_cmd = &evt_struct->iu.srp.cmd;
        memset(srp_cmd, 0x00, sizeof(*srp_cmd));
        srp_cmd->type = SRP_CMD_TYPE;
        memcpy(srp_cmd->cdb, cmnd->cmnd, sizeof(cmnd->cmnd));
        srp_cmd->lun = ((u64) lun) << 48;

        if (!map_data_for_srp_cmd(cmnd, srp_cmd, hostdata->dev)) {
                printk(KERN_ERR "ibmvscsi: couldn't convert cmd to srp_cmd\n");
                free_event_struct(&hostdata->pool, evt_struct);
                return SCSI_MLQUEUE_HOST_BUSY;
        }

        /* Fix up dma address of the buffer itself */
        if ((srp_cmd->data_out_format == SRP_INDIRECT_BUFFER) ||
            (srp_cmd->data_in_format == SRP_INDIRECT_BUFFER)) {
                struct indirect_descriptor *indirect =
                    (struct indirect_descriptor *)srp_cmd->additional_data;
                indirect->head.virtual_address = evt_struct->crq.IU_data_ptr +
                    offsetof(struct srp_cmd, additional_data) +
                    offsetof(struct indirect_descriptor, list);
        }

        return ibmvscsi_send_srp_event(evt_struct, hostdata);
}

/* ------------------------------------------------------------
 * Routines for driver initialization
 */
/**
 * adapter_info_rsp: - Handle response to MAD adapter info request
 * @evt_struct: srp_event_struct with the response
 *
 * Used as a "done" callback by when sending adapter_info. Gets called
 * by ibmvscsi_handle_crq()
*/
static void adapter_info_rsp(struct srp_event_struct *evt_struct)
{
        struct ibmvscsi_host_data *hostdata = evt_struct->hostdata;
        dma_unmap_single(hostdata->dev,
                         evt_struct->iu.mad.adapter_info.buffer,
                         evt_struct->iu.mad.adapter_info.common.length,
                         DMA_BIDIRECTIONAL);

        if (evt_struct->xfer_iu->mad.adapter_info.common.status) {
                printk("ibmvscsi: error %d getting adapter info\n",
                       evt_struct->xfer_iu->mad.adapter_info.common.status);
        } else {
                printk("ibmvscsi: host srp version: %s, "
                       "host partition %s (%d), OS %d, max io %u\n",
                       hostdata->madapter_info.srp_version,
                       hostdata->madapter_info.partition_name,
                       hostdata->madapter_info.partition_number,
                       hostdata->madapter_info.os_type,
                       hostdata->madapter_info.port_max_txu[0]);
                
                if (hostdata->madapter_info.port_max_txu[0]) 
                        hostdata->host->max_sectors = 
                                hostdata->madapter_info.port_max_txu[0] >> 9;
        }
}

/**
 * send_mad_adapter_info: - Sends the mad adapter info request
 *      and stores the result so it can be retrieved with
 *      sysfs.  We COULD consider causing a failure if the
 *      returned SRP version doesn't match ours.
 * @hostdata:   ibmvscsi_host_data of host
 * 
 * Returns zero if successful.
*/
static void send_mad_adapter_info(struct ibmvscsi_host_data *hostdata)
{
        struct viosrp_adapter_info *req;
        struct srp_event_struct *evt_struct;
        
        evt_struct = get_event_struct(&hostdata->pool);
        if (!evt_struct) {
                printk(KERN_ERR "ibmvscsi: couldn't allocate an event "
                       "for ADAPTER_INFO_REQ!\n");
                return;
        }

        init_event_struct(evt_struct,
                          adapter_info_rsp,
                          VIOSRP_MAD_FORMAT,
                          init_timeout * HZ);
        
        req = &evt_struct->iu.mad.adapter_info;
        memset(req, 0x00, sizeof(*req));
        
        req->common.type = VIOSRP_ADAPTER_INFO_TYPE;
        req->common.length = sizeof(hostdata->madapter_info);
        req->buffer = dma_map_single(hostdata->dev,
                                     &hostdata->madapter_info,
                                     sizeof(hostdata->madapter_info),
                                     DMA_BIDIRECTIONAL);

        if (dma_mapping_error(req->buffer)) {
                printk(KERN_ERR
                       "ibmvscsi: Unable to map request_buffer "
                       "for adapter_info!\n");
                free_event_struct(&hostdata->pool, evt_struct);
                return;
        }
        
        if (ibmvscsi_send_srp_event(evt_struct, hostdata))
                printk(KERN_ERR "ibmvscsi: couldn't send ADAPTER_INFO_REQ!\n");
};

/**
 * login_rsp: - Handle response to SRP login request
 * @evt_struct: srp_event_struct with the response
 *
 * Used as a "done" callback by when sending srp_login. Gets called
 * by ibmvscsi_handle_crq()
*/
static void login_rsp(struct srp_event_struct *evt_struct)
{
        struct ibmvscsi_host_data *hostdata = evt_struct->hostdata;
        switch (evt_struct->xfer_iu->srp.generic.type) {
        case SRP_LOGIN_RSP_TYPE:        /* it worked! */
                break;
        case SRP_LOGIN_REJ_TYPE:        /* refused! */
                printk(KERN_INFO "ibmvscsi: SRP_LOGIN_REQ rejected\n");
                /* Login failed.  */
                atomic_set(&hostdata->request_limit, -1);
                return;
        default:
                printk(KERN_ERR
                       "ibmvscsi: Invalid login response typecode 0x%02x!\n",
                       evt_struct->xfer_iu->srp.generic.type);
                /* Login failed.  */
                atomic_set(&hostdata->request_limit, -1);
                return;
        }

        printk(KERN_INFO "ibmvscsi: SRP_LOGIN succeeded\n");

        if (evt_struct->xfer_iu->srp.login_rsp.request_limit_delta >
            (max_requests - 2))
                evt_struct->xfer_iu->srp.login_rsp.request_limit_delta =
                    max_requests - 2;

        /* Now we know what the real request-limit is */
        atomic_set(&hostdata->request_limit,
                   evt_struct->xfer_iu->srp.login_rsp.request_limit_delta);

        hostdata->host->can_queue =
            evt_struct->xfer_iu->srp.login_rsp.request_limit_delta - 2;

        if (hostdata->host->can_queue < 1) {
                printk(KERN_ERR "ibmvscsi: Invalid request_limit_delta\n");
                return;
        }

        send_mad_adapter_info(hostdata);
        return;
}

/**
 * send_srp_login: - Sends the srp login
 * @hostdata:   ibmvscsi_host_data of host
 * 
 * Returns zero if successful.
*/
static int send_srp_login(struct ibmvscsi_host_data *hostdata)
{
        int rc;
        unsigned long flags;
        struct srp_login_req *login;
        struct srp_event_struct *evt_struct = get_event_struct(&hostdata->pool);
        if (!evt_struct) {
                printk(KERN_ERR
                       "ibmvscsi: couldn't allocate an event for login req!\n");
                return FAILED;
        }

        init_event_struct(evt_struct,
                          login_rsp,
                          VIOSRP_SRP_FORMAT,
                          init_timeout * HZ);

        login = &evt_struct->iu.srp.login_req;
        login->type = SRP_LOGIN_REQ_TYPE;
        login->max_requested_initiator_to_target_iulen = sizeof(union srp_iu);
        login->required_buffer_formats = 0x0006;
        
        /* Start out with a request limit of 1, since this is negotiated in
         * the login request we are just sending
         */
        atomic_set(&hostdata->request_limit, 1);

        spin_lock_irqsave(hostdata->host->host_lock, flags);
        rc = ibmvscsi_send_srp_event(evt_struct, hostdata);
        spin_unlock_irqrestore(hostdata->host->host_lock, flags);
        return rc;
};

/**
 * sync_completion: Signal that a synchronous command has completed
 * Note that after returning from this call, the evt_struct is freed.
 * the caller waiting on this completion shouldn't touch the evt_struct
 * again.
 */
static void sync_completion(struct srp_event_struct *evt_struct)
{
        /* copy the response back */
        if (evt_struct->sync_srp)
                *evt_struct->sync_srp = *evt_struct->xfer_iu;
        
        complete(&evt_struct->comp);
}

/**
 * ibmvscsi_abort: Abort a command...from scsi host template
 * send this over to the server and wait synchronously for the response
 */
static int ibmvscsi_eh_abort_handler(struct scsi_cmnd *cmd)
{
        struct ibmvscsi_host_data *hostdata =
            (struct ibmvscsi_host_data *)cmd->device->host->hostdata;
        struct srp_tsk_mgmt *tsk_mgmt;
        struct srp_event_struct *evt;
        struct srp_event_struct *tmp_evt, *found_evt;
        union viosrp_iu srp_rsp;
        int rsp_rc;
        u16 lun = lun_from_dev(cmd->device);

        /* First, find this command in our sent list so we can figure
         * out the correct tag
         */
        found_evt = NULL;
        list_for_each_entry(tmp_evt, &hostdata->sent, list) {
                if (tmp_evt->cmnd == cmd) {
                        found_evt = tmp_evt;
                        break;
                }
        }

        if (!found_evt) 
                return FAILED;

        evt = get_event_struct(&hostdata->pool);
        if (evt == NULL) {
                printk(KERN_ERR "ibmvscsi: failed to allocate abort event\n");
                return FAILED;
        }
        
        init_event_struct(evt,
                          sync_completion,
                          VIOSRP_SRP_FORMAT,
                          init_timeout * HZ);

        tsk_mgmt = &evt->iu.srp.tsk_mgmt;
        
        /* Set up an abort SRP command */
        memset(tsk_mgmt, 0x00, sizeof(*tsk_mgmt));
        tsk_mgmt->type = SRP_TSK_MGMT_TYPE;
        tsk_mgmt->lun = ((u64) lun) << 48;
        tsk_mgmt->task_mgmt_flags = 0x01;       /* ABORT TASK */
        tsk_mgmt->managed_task_tag = (u64) found_evt;

        printk(KERN_INFO "ibmvscsi: aborting command. lun 0x%lx, tag 0x%lx\n",
               tsk_mgmt->lun, tsk_mgmt->managed_task_tag);

        evt->sync_srp = &srp_rsp;
        init_completion(&evt->comp);
        if (ibmvscsi_send_srp_event(evt, hostdata) != 0) {
                printk(KERN_ERR "ibmvscsi: failed to send abort() event\n");
                return FAILED;
        }

        wait_for_completion(&evt->comp);

        /* make sure we got a good response */
        if (unlikely(srp_rsp.srp.generic.type != SRP_RSP_TYPE)) {
                if (printk_ratelimit())
                        printk(KERN_WARNING 
                               "ibmvscsi: abort bad SRP RSP type %d\n",
                               srp_rsp.srp.generic.type);
                return FAILED;
        }

        if (srp_rsp.srp.rsp.rspvalid)
                rsp_rc = *((int *)srp_rsp.srp.rsp.sense_and_response_data);
        else
                rsp_rc = srp_rsp.srp.rsp.status;

        if (rsp_rc) {
                if (printk_ratelimit())
                        printk(KERN_WARNING 
                       "ibmvscsi: abort code %d for task tag 0x%lx\n",
                               rsp_rc,
                               tsk_mgmt->managed_task_tag);
                return FAILED;
        }

        /* Because we dropped the spinlock above, it's possible
         * The event is no longer in our list.  Make sure it didn't
         * complete while we were aborting
         */
        found_evt = NULL;
        list_for_each_entry(tmp_evt, &hostdata->sent, list) {
                if (tmp_evt->cmnd == cmd) {
                        found_evt = tmp_evt;
                        break;
                }
        }

        if (found_evt == NULL) {
                printk(KERN_INFO
                       "ibmvscsi: aborted task tag 0x%lx completed\n",
                       tsk_mgmt->managed_task_tag);
                return SUCCESS;
        }

        printk(KERN_INFO
               "ibmvscsi: successfully aborted task tag 0x%lx\n",
               tsk_mgmt->managed_task_tag);

        cmd->result = (DID_ABORT << 16);
        list_del(&found_evt->list);
        unmap_cmd_data(&found_evt->iu.srp.cmd, found_evt->hostdata->dev);
        free_event_struct(&found_evt->hostdata->pool, found_evt);
        atomic_inc(&hostdata->request_limit);
        return SUCCESS;
}

/**
 * ibmvscsi_eh_device_reset_handler: Reset a single LUN...from scsi host 
 * template send this over to the server and wait synchronously for the 
 * response
 */
static int ibmvscsi_eh_device_reset_handler(struct scsi_cmnd *cmd)
{
        struct ibmvscsi_host_data *hostdata =
            (struct ibmvscsi_host_data *)cmd->device->host->hostdata;

        struct srp_tsk_mgmt *tsk_mgmt;
        struct srp_event_struct *evt;
        struct srp_event_struct *tmp_evt, *pos;
        union viosrp_iu srp_rsp;
        int rsp_rc;
        u16 lun = lun_from_dev(cmd->device);

        evt = get_event_struct(&hostdata->pool);
        if (evt == NULL) {
                printk(KERN_ERR "ibmvscsi: failed to allocate reset event\n");
                return FAILED;
        }
        
        init_event_struct(evt,
                          sync_completion,
                          VIOSRP_SRP_FORMAT,
                          init_timeout * HZ);

        tsk_mgmt = &evt->iu.srp.tsk_mgmt;

        /* Set up a lun reset SRP command */
        memset(tsk_mgmt, 0x00, sizeof(*tsk_mgmt));
        tsk_mgmt->type = SRP_TSK_MGMT_TYPE;
        tsk_mgmt->lun = ((u64) lun) << 48;
        tsk_mgmt->task_mgmt_flags = 0x08;       /* LUN RESET */

        printk(KERN_INFO "ibmvscsi: resetting device. lun 0x%lx\n",
               tsk_mgmt->lun);

        evt->sync_srp = &srp_rsp;
        init_completion(&evt->comp);
        if (ibmvscsi_send_srp_event(evt, hostdata) != 0) {
                printk(KERN_ERR "ibmvscsi: failed to send reset event\n");
                return FAILED;
        }

        wait_for_completion(&evt->comp);

        /* make sure we got a good response */
        if (unlikely(srp_rsp.srp.generic.type != SRP_RSP_TYPE)) {
                if (printk_ratelimit())
                        printk(KERN_WARNING 
                               "ibmvscsi: reset bad SRP RSP type %d\n",
                               srp_rsp.srp.generic.type);
                return FAILED;
        }

        if (srp_rsp.srp.rsp.rspvalid)
                rsp_rc = *((int *)srp_rsp.srp.rsp.sense_and_response_data);
        else
                rsp_rc = srp_rsp.srp.rsp.status;

        if (rsp_rc) {
                if (printk_ratelimit())
                        printk(KERN_WARNING 
                               "ibmvscsi: reset code %d for task tag 0x%lx\n",
                       rsp_rc,
                               tsk_mgmt->managed_task_tag);
                return FAILED;
        }

        /* We need to find all commands for this LUN that have not yet been
         * responded to, and fail them with DID_RESET
         */
        list_for_each_entry_safe(tmp_evt, pos, &hostdata->sent, list) {
                if ((tmp_evt->cmnd) && (tmp_evt->cmnd->device == cmd->device)) {
                        if (tmp_evt->cmnd)
                                tmp_evt->cmnd->result = (DID_RESET << 16);
                        list_del(&tmp_evt->list);
                        unmap_cmd_data(&tmp_evt->iu.srp.cmd, tmp_evt->hostdata->dev);
                        free_event_struct(&tmp_evt->hostdata->pool,
                                                   tmp_evt);
                        atomic_inc(&hostdata->request_limit);
                        if (tmp_evt->cmnd_done)
                                tmp_evt->cmnd_done(tmp_evt->cmnd);
                        else if (tmp_evt->done)
                                tmp_evt->done(tmp_evt);
                }
        }
        return SUCCESS;
}

/**
 * purge_requests: Our virtual adapter just shut down.  purge any sent requests
 * @hostdata:    the adapter
 */
static void purge_requests(struct ibmvscsi_host_data *hostdata)
{
        struct srp_event_struct *tmp_evt, *pos;
        unsigned long flags;

        spin_lock_irqsave(hostdata->host->host_lock, flags);
        list_for_each_entry_safe(tmp_evt, pos, &hostdata->sent, list) {
                list_del(&tmp_evt->list);
                if (tmp_evt->cmnd) {
                        tmp_evt->cmnd->result = (DID_ERROR << 16);
                        unmap_cmd_data(&tmp_evt->iu.srp.cmd, 
                                       tmp_evt->hostdata->dev);
                        if (tmp_evt->cmnd_done)
                                tmp_evt->cmnd_done(tmp_evt->cmnd);
                } else {
                        if (tmp_evt->done) {
                                tmp_evt->done(tmp_evt);
                        }
                }
                free_event_struct(&tmp_evt->hostdata->pool, tmp_evt);
        }
        spin_unlock_irqrestore(hostdata->host->host_lock, flags);
}

/**
 * ibmvscsi_handle_crq: - Handles and frees received events in the CRQ
 * @crq:        Command/Response queue
 * @hostdata:   ibmvscsi_host_data of host
 *
*/
void ibmvscsi_handle_crq(struct viosrp_crq *crq,
                         struct ibmvscsi_host_data *hostdata)
{
        unsigned long flags;
        struct srp_event_struct *evt_struct =
            (struct srp_event_struct *)crq->IU_data_ptr;
        switch (crq->valid) {
        case 0xC0:              /* initialization */
                switch (crq->format) {
                case 0x01:      /* Initialization message */
                        printk(KERN_INFO "ibmvscsi: partner initialized\n");
                        /* Send back a response */
                        if (ibmvscsi_send_crq(hostdata,
                                              0xC002000000000000LL, 0) == 0) {
                                /* Now login */
                                send_srp_login(hostdata);
                        } else {
                                printk(KERN_ERR
                                       "ibmvscsi: Unable to send init rsp\n");
                        }

                        break;
                case 0x02:      /* Initialization response */
                        printk(KERN_INFO
                               "ibmvscsi: partner initialization complete\n");

                        /* Now login */
                        send_srp_login(hostdata);
                        break;
                default:
                        printk(KERN_ERR "ibmvscsi: unknown crq message type\n");
                }
                return;
        case 0xFF:              /* Hypervisor telling us the connection is closed */
                printk(KERN_INFO "ibmvscsi: Virtual adapter failed!\n");

                atomic_set(&hostdata->request_limit, -1);
                purge_requests(hostdata);
                ibmvscsi_reset_crq_queue(&hostdata->queue, hostdata);
                return;
        case 0x80:              /* real payload */
                break;
        default:
                printk(KERN_ERR
                       "ibmvscsi: got an invalid message type 0x%02x\n",
                       crq->valid);
                return;
        }

        /* The only kind of payload CRQs we should get are responses to
         * things we send. Make sure this response is to something we
         * actually sent
         */
        if (!valid_event_struct(&hostdata->pool, evt_struct)) {
                printk(KERN_ERR
                       "ibmvscsi: returned correlation_token 0x%p is invalid!\n",
                       (void *)crq->IU_data_ptr);
                return;
        }

        if (atomic_read(&evt_struct->free)) {
                printk(KERN_ERR
                       "ibmvscsi: received duplicate  correlation_token 0x%p!\n",
                       (void *)crq->IU_data_ptr);
                return;
        }

        if (crq->format == VIOSRP_SRP_FORMAT)
                atomic_add(evt_struct->xfer_iu->srp.rsp.request_limit_delta,
                           &hostdata->request_limit);

        if (evt_struct->done)
                evt_struct->done(evt_struct);
        else
                printk(KERN_ERR
                       "ibmvscsi: returned done() is NULL; not running it!\n");

        /*
         * Lock the host_lock before messing with these structures, since we
         * are running in a task context
         */
        spin_lock_irqsave(evt_struct->hostdata->host->host_lock, flags);
        list_del(&evt_struct->list);
        free_event_struct(&evt_struct->hostdata->pool, evt_struct);
        spin_unlock_irqrestore(evt_struct->hostdata->host->host_lock, flags);
}

/**
 * ibmvscsi_get_host_config: Send the command to the server to get host
 * configuration data.  The data is opaque to us.
 */
static int ibmvscsi_do_host_config(struct ibmvscsi_host_data *hostdata,
                                   unsigned char *buffer, int length)
{
        struct viosrp_host_config *host_config;
        struct srp_event_struct *evt_struct;
        int rc;

        evt_struct = get_event_struct(&hostdata->pool);
        if (!evt_struct) {
                printk(KERN_ERR
                       "ibmvscsi: could't allocate event for HOST_CONFIG!\n");
                return -1;
        }

        init_event_struct(evt_struct,
                          sync_completion,
                          VIOSRP_MAD_FORMAT,
                          init_timeout * HZ);

        host_config = &evt_struct->iu.mad.host_config;

        /* Set up a lun reset SRP command */
        memset(host_config, 0x00, sizeof(*host_config));
        host_config->common.type = VIOSRP_HOST_CONFIG_TYPE;
        host_config->common.length = length;
        host_config->buffer = dma_map_single(hostdata->dev, buffer, length,
                                            DMA_BIDIRECTIONAL);

        if (dma_mapping_error(host_config->buffer)) {
                printk(KERN_ERR
                       "ibmvscsi: dma_mapping error " "getting host config\n");
                free_event_struct(&hostdata->pool, evt_struct);
                return -1;
        }

        init_completion(&evt_struct->comp);
        rc = ibmvscsi_send_srp_event(evt_struct, hostdata);
        if (rc == 0) {
                wait_for_completion(&evt_struct->comp);
                dma_unmap_single(hostdata->dev, host_config->buffer,
                                 length, DMA_BIDIRECTIONAL);
        }

        return rc;
}

/* ------------------------------------------------------------
 * sysfs attributes
 */
static ssize_t show_host_srp_version(struct class_device *class_dev, char *buf)
{
        struct Scsi_Host *shost = class_to_shost(class_dev);
        struct ibmvscsi_host_data *hostdata =
            (struct ibmvscsi_host_data *)shost->hostdata;
        int len;

        len = snprintf(buf, PAGE_SIZE, "%s\n",
                       hostdata->madapter_info.srp_version);
        return len;
}

static struct class_device_attribute ibmvscsi_host_srp_version = {
        .attr = {
                 .name = "srp_version",
                 .mode = S_IRUGO,
                 },
        .show = show_host_srp_version,
};

static ssize_t show_host_partition_name(struct class_device *class_dev,
                                        char *buf)
{
        struct Scsi_Host *shost = class_to_shost(class_dev);
        struct ibmvscsi_host_data *hostdata =
            (struct ibmvscsi_host_data *)shost->hostdata;
        int len;

        len = snprintf(buf, PAGE_SIZE, "%s\n",
                       hostdata->madapter_info.partition_name);
        return len;
}

static struct class_device_attribute ibmvscsi_host_partition_name = {
        .attr = {
                 .name = "partition_name",
                 .mode = S_IRUGO,
                 },
        .show = show_host_partition_name,
};

static ssize_t show_host_partition_number(struct class_device *class_dev,
                                          char *buf)
{
        struct Scsi_Host *shost = class_to_shost(class_dev);
        struct ibmvscsi_host_data *hostdata =
            (struct ibmvscsi_host_data *)shost->hostdata;
        int len;

        len = snprintf(buf, PAGE_SIZE, "%d\n",
                       hostdata->madapter_info.partition_number);
        return len;
}

static struct class_device_attribute ibmvscsi_host_partition_number = {
        .attr = {
                 .name = "partition_number",
                 .mode = S_IRUGO,
                 },
        .show = show_host_partition_number,
};

static ssize_t show_host_mad_version(struct class_device *class_dev, char *buf)
{
        struct Scsi_Host *shost = class_to_shost(class_dev);
        struct ibmvscsi_host_data *hostdata =
            (struct ibmvscsi_host_data *)shost->hostdata;
        int len;

        len = snprintf(buf, PAGE_SIZE, "%d\n",
                       hostdata->madapter_info.mad_version);
        return len;
}

static struct class_device_attribute ibmvscsi_host_mad_version = {
        .attr = {
                 .name = "mad_version",
                 .mode = S_IRUGO,
                 },
        .show = show_host_mad_version,
};

static ssize_t show_host_os_type(struct class_device *class_dev, char *buf)
{
        struct Scsi_Host *shost = class_to_shost(class_dev);
        struct ibmvscsi_host_data *hostdata =
            (struct ibmvscsi_host_data *)shost->hostdata;
        int len;

        len = snprintf(buf, PAGE_SIZE, "%d\n", hostdata->madapter_info.os_type);
        return len;
}

static struct class_device_attribute ibmvscsi_host_os_type = {
        .attr = {
                 .name = "os_type",
                 .mode = S_IRUGO,
                 },
        .show = show_host_os_type,
};

static ssize_t show_host_config(struct class_device *class_dev, char *buf)
{
        struct Scsi_Host *shost = class_to_shost(class_dev);
        struct ibmvscsi_host_data *hostdata =
            (struct ibmvscsi_host_data *)shost->hostdata;

        /* returns null-terminated host config data */
        if (ibmvscsi_do_host_config(hostdata, buf, PAGE_SIZE) == 0)
                return strlen(buf);
        else
                return 0;
}

static struct class_device_attribute ibmvscsi_host_config = {
        .attr = {
                 .name = "config",
                 .mode = S_IRUGO,
                 },
        .show = show_host_config,
};

static struct class_device_attribute *ibmvscsi_attrs[] = {
        &ibmvscsi_host_srp_version,
        &ibmvscsi_host_partition_name,
        &ibmvscsi_host_partition_number,
        &ibmvscsi_host_mad_version,
        &ibmvscsi_host_os_type,
        &ibmvscsi_host_config,
        NULL
};

/* ------------------------------------------------------------
 * SCSI driver registration
 */
static struct scsi_host_template driver_template = {
        .module = THIS_MODULE,
        .name = "IBM POWER Virtual SCSI Adapter " IBMVSCSI_VERSION,
        .proc_name = "ibmvscsi",
        .queuecommand = ibmvscsi_queuecommand,
        .eh_abort_handler = ibmvscsi_eh_abort_handler,
        .eh_device_reset_handler = ibmvscsi_eh_device_reset_handler,
        .cmd_per_lun = 16,
        .can_queue = 1,         /* Updated after SRP_LOGIN */
        .this_id = -1,
        .sg_tablesize = MAX_INDIRECT_BUFS,
        .use_clustering = ENABLE_CLUSTERING,
        .shost_attrs = ibmvscsi_attrs,
};

/**
 * Called by bus code for each adapter
 */
static int ibmvscsi_probe(struct vio_dev *vdev, const struct vio_device_id *id)
{
        struct ibmvscsi_host_data *hostdata;
        struct Scsi_Host *host;
        struct device *dev = &vdev->dev;
        unsigned long wait_switch = 0;

        vdev->dev.driver_data = NULL;

        host = scsi_host_alloc(&driver_template, sizeof(*hostdata));
        if (!host) {
                printk(KERN_ERR "ibmvscsi: couldn't allocate host data\n");
                goto scsi_host_alloc_failed;
        }

        hostdata = (struct ibmvscsi_host_data *)host->hostdata;
        memset(hostdata, 0x00, sizeof(*hostdata));
        INIT_LIST_HEAD(&hostdata->sent);
        hostdata->host = host;
        hostdata->dev = dev;
        atomic_set(&hostdata->request_limit, -1);
        hostdata->host->max_sectors = 32 * 8; /* default max I/O 32 pages */

        if (ibmvscsi_init_crq_queue(&hostdata->queue, hostdata,
                                    max_requests) != 0) {
                printk(KERN_ERR "ibmvscsi: couldn't initialize crq\n");
                goto init_crq_failed;
        }
        if (initialize_event_pool(&hostdata->pool, max_requests, hostdata) != 0) {
                printk(KERN_ERR "ibmvscsi: couldn't initialize event pool\n");
                goto init_pool_failed;
        }

        host->max_lun = 8;
        host->max_id = max_id;
        host->max_channel = max_channel;

        if (scsi_add_host(hostdata->host, hostdata->dev))
                goto add_host_failed;

        /* Try to send an initialization message.  Note that this is allowed
         * to fail if the other end is not acive.  In that case we don't
         * want to scan
         */
        if (ibmvscsi_send_crq(hostdata, 0xC001000000000000LL, 0) == 0) {
                /*
                 * Wait around max init_timeout secs for the adapter to finish
                 * initializing. When we are done initializing, we will have a
                 * valid request_limit.  We don't want Linux scanning before
                 * we are ready.
                 */
                for (wait_switch = jiffies + (init_timeout * HZ);
                     time_before(jiffies, wait_switch) &&
                     atomic_read(&hostdata->request_limit) < 2;) {

                        msleep(10);
                }

                /* if we now have a valid request_limit, initiate a scan */
                if (atomic_read(&hostdata->request_limit) > 0)
                        scsi_scan_host(host);
        }

        vdev->dev.driver_data = hostdata;
        return 0;

      add_host_failed:
        release_event_pool(&hostdata->pool, hostdata);
      init_pool_failed:
        ibmvscsi_release_crq_queue(&hostdata->queue, hostdata, max_requests);
      init_crq_failed:
        scsi_host_put(host);
      scsi_host_alloc_failed:
        return -1;
}

static int ibmvscsi_remove(struct vio_dev *vdev)
{
        struct ibmvscsi_host_data *hostdata = vdev->dev.driver_data;
        release_event_pool(&hostdata->pool, hostdata);
        ibmvscsi_release_crq_queue(&hostdata->queue, hostdata,
                                   max_requests);
        
        scsi_remove_host(hostdata->host);
        scsi_host_put(hostdata->host);

        return 0;
}

/**
 * ibmvscsi_device_table: Used by vio.c to match devices in the device tree we 
 * support.
 */
static struct vio_device_id ibmvscsi_device_table[] __devinitdata = {
        {"vscsi", "IBM,v-scsi"},
        {0,}
};

MODULE_DEVICE_TABLE(vio, ibmvscsi_device_table);
static struct vio_driver ibmvscsi_driver = {
        .name = "ibmvscsi",
        .id_table = ibmvscsi_device_table,
        .probe = ibmvscsi_probe,
        .remove = ibmvscsi_remove
};

int __init ibmvscsi_module_init(void)
{
        return vio_register_driver(&ibmvscsi_driver);
}

void __exit ibmvscsi_module_exit(void)
{
        vio_unregister_driver(&ibmvscsi_driver);
}

module_init(ibmvscsi_module_init);
module_exit(ibmvscsi_module_exit);