Merge branch 'linus' into x86/core

[linux-2.6] / sound / oss / vwsnd.c

/*
 * Sound driver for Silicon Graphics 320 and 540 Visual Workstations'
 * onboard audio.  See notes in Documentation/sound/oss/vwsnd .
 *
 * Copyright 1999 Silicon Graphics, Inc.  All rights reserved.
 *
 * 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., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#undef VWSND_DEBUG                      /* define for debugging */

/*
 * XXX to do -
 *
 *      External sync.
 *      Rename swbuf, hwbuf, u&i, hwptr&swptr to something rational.
 *      Bug - if select() called before read(), pcm_setup() not called.
 *      Bug - output doesn't stop soon enough if process killed.
 */

/*
 * Things to test -
 *
 *      Will readv/writev work?  Write a test.
 *
 *      insmod/rmmod 100 million times.
 *
 *      Run I/O until int ptrs wrap around (roughly 6.2 hours @ DAT
 *      rate).
 *
 *      Concurrent threads banging on mixer simultaneously, both UP
 *      and SMP kernels.  Especially, watch for thread A changing
 *      OUTSRC while thread B changes gain -- both write to the same
 *      ad1843 register.
 *
 *      What happens if a client opens /dev/audio then forks?
 *      Do two procs have /dev/audio open?  Test.
 *
 *      Pump audio through the CD, MIC and line inputs and verify that
 *      they mix/mute into the output.
 *
 *      Apps:
 *              amp
 *              mpg123
 *              x11amp
 *              mxv
 *              kmedia
 *              esound
 *              need more input apps
 *
 *      Run tests while bombarding with signals.  setitimer(2) will do it...  */

/*
 * This driver is organized in nine sections.
 * The nine sections are:
 *
 *      debug stuff
 *      low level lithium access
 *      high level lithium access
 *      AD1843 access
 *      PCM I/O
 *      audio driver
 *      mixer driver
 *      probe/attach/unload
 *      initialization and loadable kernel module interface
 *
 * That is roughly the order of increasing abstraction, so forward
 * dependencies are minimal.
 */

/*
 * Locking Notes
 *
 *      INC_USE_COUNT and DEC_USE_COUNT keep track of the number of
 *      open descriptors to this driver. They store it in vwsnd_use_count.
 *      The global device list, vwsnd_dev_list, is immutable when the IN_USE
 *      is true.
 *
 *      devc->open_lock is a semaphore that is used to enforce the
 *      single reader/single writer rule for /dev/audio.  The rule is
 *      that each device may have at most one reader and one writer.
 *      Open will block until the previous client has closed the
 *      device, unless O_NONBLOCK is specified.
 *
 *      The semaphore devc->io_mutex serializes PCM I/O syscalls.  This
 *      is unnecessary in Linux 2.2, because the kernel lock
 *      serializes read, write, and ioctl globally, but it's there,
 *      ready for the brave, new post-kernel-lock world.
 *
 *      Locking between interrupt and baselevel is handled by the
 *      "lock" spinlock in vwsnd_port (one lock each for read and
 *      write).  Each half holds the lock just long enough to see what
 *      area it owns and update its pointers.  See pcm_output() and
 *      pcm_input() for most of the gory stuff.
 *
 *      devc->mix_mutex serializes all mixer ioctls.  This is also
 *      redundant because of the kernel lock.
 *
 *      The lowest level lock is lith->lithium_lock.  It is a
 *      spinlock which is held during the two-register tango of
 *      reading/writing an AD1843 register.  See
 *      li_{read,write}_ad1843_reg().
 */

/*
 * Sample Format Notes
 *
 *      Lithium's DMA engine has two formats: 16-bit 2's complement
 *      and 8-bit unsigned .  16-bit transfers the data unmodified, 2
 *      bytes per sample.  8-bit unsigned transfers 1 byte per sample
 *      and XORs each byte with 0x80.  Lithium can input or output
 *      either mono or stereo in either format.
 *
 *      The AD1843 has four formats: 16-bit 2's complement, 8-bit
 *      unsigned, 8-bit mu-Law and 8-bit A-Law.
 *
 *      This driver supports five formats: AFMT_S8, AFMT_U8,
 *      AFMT_MU_LAW, AFMT_A_LAW, and AFMT_S16_LE.
 *
 *      For AFMT_U8 output, we keep the AD1843 in 16-bit mode, and
 *      rely on Lithium's XOR to translate between U8 and S8.
 *
 *      For AFMT_S8, AFMT_MU_LAW and AFMT_A_LAW output, we have to XOR
 *      the 0x80 bit in software to compensate for Lithium's XOR.
 *      This happens in pcm_copy_{in,out}().
 *
 * Changes:
 * 11-10-2000   Bartlomiej Zolnierkiewicz <bkz@linux-ide.org>
 *              Added some __init/__exit
 */

#include <linux/module.h>
#include <linux/init.h>

#include <linux/spinlock.h>
#include <linux/smp_lock.h>
#include <linux/wait.h>
#include <linux/interrupt.h>
#include <linux/mutex.h>

#include <asm/visws/cobalt.h>

#include "sound_config.h"

/*****************************************************************************/
/* debug stuff */

#ifdef VWSND_DEBUG

static int shut_up = 1;

/*
 * dbgassert - called when an assertion fails.
 */

static void dbgassert(const char *fcn, int line, const char *expr)
{
        if (in_interrupt())
                panic("ASSERTION FAILED IN INTERRUPT, %s:%s:%d %s\n",
                      __FILE__, fcn, line, expr);
        else {
                int x;
                printk(KERN_ERR "ASSERTION FAILED, %s:%s:%d %s\n",
                       __FILE__, fcn, line, expr);
                x = * (volatile int *) 0; /* force proc to exit */
        }
}

/*
 * Bunch of useful debug macros:
 *
 *      ASSERT  - print unless e nonzero (panic if in interrupt)
 *      DBGDO   - include arbitrary code if debugging
 *      DBGX    - debug print raw (w/o function name)
 *      DBGP    - debug print w/ function name
 *      DBGE    - debug print function entry
 *      DBGC    - debug print function call
 *      DBGR    - debug print function return
 *      DBGXV   - debug print raw when verbose
 *      DBGPV   - debug print when verbose
 *      DBGEV   - debug print function entry when verbose
 *      DBGRV   - debug print function return when verbose
 */

#define ASSERT(e)      ((e) ? (void) 0 : dbgassert(__func__, __LINE__, #e))
#define DBGDO(x)            x
#define DBGX(fmt, args...)  (in_interrupt() ? 0 : printk(KERN_ERR fmt, ##args))
#define DBGP(fmt, args...)  (DBGX("%s: " fmt, __func__ , ##args))
#define DBGE(fmt, args...)  (DBGX("%s" fmt, __func__ , ##args))
#define DBGC(rtn)           (DBGP("calling %s\n", rtn))
#define DBGR()              (DBGP("returning\n"))
#define DBGXV(fmt, args...) (shut_up ? 0 : DBGX(fmt, ##args))
#define DBGPV(fmt, args...) (shut_up ? 0 : DBGP(fmt, ##args))
#define DBGEV(fmt, args...) (shut_up ? 0 : DBGE(fmt, ##args))
#define DBGCV(rtn)          (shut_up ? 0 : DBGC(rtn))
#define DBGRV()             (shut_up ? 0 : DBGR())

#else /* !VWSND_DEBUG */

#define ASSERT(e)           ((void) 0)
#define DBGDO(x)            /* don't */
#define DBGX(fmt, args...)  ((void) 0)
#define DBGP(fmt, args...)  ((void) 0)
#define DBGE(fmt, args...)  ((void) 0)
#define DBGC(rtn)           ((void) 0)
#define DBGR()              ((void) 0)
#define DBGPV(fmt, args...) ((void) 0)
#define DBGXV(fmt, args...) ((void) 0)
#define DBGEV(fmt, args...) ((void) 0)
#define DBGCV(rtn)          ((void) 0)
#define DBGRV()             ((void) 0)

#endif /* !VWSND_DEBUG */

/*****************************************************************************/
/* low level lithium access */

/*
 * We need to talk to Lithium registers on three pages.  Here are
 * the pages' offsets from the base address (0xFF001000).
 */

enum {
        LI_PAGE0_OFFSET = 0x01000 - 0x1000, /* FF001000 */
        LI_PAGE1_OFFSET = 0x0F000 - 0x1000, /* FF00F000 */
        LI_PAGE2_OFFSET = 0x10000 - 0x1000, /* FF010000 */
};

/* low-level lithium data */

typedef struct lithium {
        void *          page0;          /* virtual addresses */
        void *          page1;
        void *          page2;
        spinlock_t      lock;           /* protects codec and UST/MSC access */
} lithium_t;

/*
 * li_destroy destroys the lithium_t structure and vm mappings.
 */

static void li_destroy(lithium_t *lith)
{
        if (lith->page0) {
                iounmap(lith->page0);
                lith->page0 = NULL;
        }
        if (lith->page1) {
                iounmap(lith->page1);
                lith->page1 = NULL;
        }
        if (lith->page2) {
                iounmap(lith->page2);
                lith->page2 = NULL;
        }
}

/*
 * li_create initializes the lithium_t structure and sets up vm mappings
 * to access the registers.
 * Returns 0 on success, -errno on failure.
 */

static int __init li_create(lithium_t *lith, unsigned long baseaddr)
{
        spin_lock_init(&lith->lock);
        lith->page0 = ioremap_nocache(baseaddr + LI_PAGE0_OFFSET, PAGE_SIZE);
        lith->page1 = ioremap_nocache(baseaddr + LI_PAGE1_OFFSET, PAGE_SIZE);
        lith->page2 = ioremap_nocache(baseaddr + LI_PAGE2_OFFSET, PAGE_SIZE);
        if (!lith->page0 || !lith->page1 || !lith->page2) {
                li_destroy(lith);
                return -ENOMEM;
        }
        return 0;
}

/*
 * basic register accessors - read/write long/byte
 */

static __inline__ unsigned long li_readl(lithium_t *lith, int off)
{
        return * (volatile unsigned long *) (lith->page0 + off);
}

static __inline__ unsigned char li_readb(lithium_t *lith, int off)
{
        return * (volatile unsigned char *) (lith->page0 + off);
}

static __inline__ void li_writel(lithium_t *lith, int off, unsigned long val)
{
        * (volatile unsigned long *) (lith->page0 + off) = val;
}

static __inline__ void li_writeb(lithium_t *lith, int off, unsigned char val)
{
        * (volatile unsigned char *) (lith->page0 + off) = val;
}

/*****************************************************************************/
/* High Level Lithium Access */

/*
 * Lithium DMA Notes
 *
 * Lithium has two dedicated DMA channels for audio.  They are known
 * as comm1 and comm2 (communication areas 1 and 2).  Comm1 is for
 * input, and comm2 is for output.  Each is controlled by three
 * registers: BASE (base address), CFG (config) and CCTL
 * (config/control).
 *
 * Each DMA channel points to a physically contiguous ring buffer in
 * main memory of up to 8 Kbytes.  (This driver always uses 8 Kb.)
 * There are three pointers into the ring buffer: read, write, and
 * trigger.  The pointers are 8 bits each.  Each pointer points to
 * 32-byte "chunks" of data.  The DMA engine moves 32 bytes at a time,
 * so there is no finer-granularity control.
 *
 * In comm1, the hardware updates the write ptr, and software updates
 * the read ptr.  In comm2, it's the opposite: hardware updates the
 * read ptr, and software updates the write ptr.  I designate the
 * hardware-updated ptr as the hwptr, and the software-updated ptr as
 * the swptr.
 *
 * The trigger ptr and trigger mask are used to trigger interrupts.
 * From the Lithium spec, section 5.6.8, revision of 12/15/1998:
 *
 *      Trigger Mask Value
 *
 *      A three bit wide field that represents a power of two mask
 *      that is used whenever the trigger pointer is compared to its
 *      respective read or write pointer.  A value of zero here
 *      implies a mask of 0xFF and a value of seven implies a mask
 *      0x01.  This value can be used to sub-divide the ring buffer
 *      into pie sections so that interrupts monitor the progress of
 *      hardware from section to section.
 *
 * My interpretation of that is, whenever the hw ptr is updated, it is
 * compared with the trigger ptr, and the result is masked by the
 * trigger mask.  (Actually, by the complement of the trigger mask.)
 * If the result is zero, an interrupt is triggered.  I.e., interrupt
 * if ((hwptr & ~mask) == (trptr & ~mask)).  The mask is formed from
 * the trigger register value as mask = (1 << (8 - tmreg)) - 1.
 *
 * In yet different words, setting tmreg to 0 causes an interrupt after
 * every 256 DMA chunks (8192 bytes) or once per traversal of the
 * ring buffer.  Setting it to 7 caues an interrupt every 2 DMA chunks
 * (64 bytes) or 128 times per traversal of the ring buffer.
 */

/* Lithium register offsets and bit definitions */

#define LI_HOST_CONTROLLER      0x000
# define LI_HC_RESET             0x00008000
# define LI_HC_LINK_ENABLE       0x00004000
# define LI_HC_LINK_FAILURE      0x00000004
# define LI_HC_LINK_CODEC        0x00000002
# define LI_HC_LINK_READY        0x00000001

#define LI_INTR_STATUS          0x010
#define LI_INTR_MASK            0x014
# define LI_INTR_LINK_ERR        0x00008000
# define LI_INTR_COMM2_TRIG      0x00000008
# define LI_INTR_COMM2_UNDERFLOW 0x00000004
# define LI_INTR_COMM1_TRIG      0x00000002
# define LI_INTR_COMM1_OVERFLOW  0x00000001

#define LI_CODEC_COMMAND        0x018
# define LI_CC_BUSY              0x00008000
# define LI_CC_DIR               0x00000080
#  define LI_CC_DIR_RD            LI_CC_DIR
#  define LI_CC_DIR_WR          (!LI_CC_DIR)
# define LI_CC_ADDR_MASK         0x0000007F

#define LI_CODEC_DATA           0x01C

#define LI_COMM1_BASE           0x100
#define LI_COMM1_CTL            0x104
# define LI_CCTL_RESET           0x80000000
# define LI_CCTL_SIZE            0x70000000
# define LI_CCTL_DMA_ENABLE      0x08000000
# define LI_CCTL_TMASK           0x07000000 /* trigger mask */
# define LI_CCTL_TPTR            0x00FF0000 /* trigger pointer */
# define LI_CCTL_RPTR            0x0000FF00
# define LI_CCTL_WPTR            0x000000FF
#define LI_COMM1_CFG            0x108
# define LI_CCFG_LOCK            0x00008000
# define LI_CCFG_SLOT            0x00000070
# define LI_CCFG_DIRECTION       0x00000008
#  define LI_CCFG_DIR_IN        (!LI_CCFG_DIRECTION)
#  define LI_CCFG_DIR_OUT         LI_CCFG_DIRECTION
# define LI_CCFG_MODE            0x00000004
#  define LI_CCFG_MODE_MONO     (!LI_CCFG_MODE)
#  define LI_CCFG_MODE_STEREO     LI_CCFG_MODE
# define LI_CCFG_FORMAT          0x00000003
#  define LI_CCFG_FMT_8BIT        0x00000000
#  define LI_CCFG_FMT_16BIT       0x00000001
#define LI_COMM2_BASE           0x10C
#define LI_COMM2_CTL            0x110
 /* bit definitions are the same as LI_COMM1_CTL */
#define LI_COMM2_CFG            0x114
 /* bit definitions are the same as LI_COMM1_CFG */

#define LI_UST_LOW              0x200   /* 64-bit Unadjusted System Time is */
#define LI_UST_HIGH             0x204   /* microseconds since boot */

#define LI_AUDIO1_UST           0x300   /* UST-MSC pairs */
#define LI_AUDIO1_MSC           0x304   /* MSC (Media Stream Counter) */
#define LI_AUDIO2_UST           0x308   /* counts samples actually */
#define LI_AUDIO2_MSC           0x30C   /* processed as of time UST */

/* 
 * Lithium's DMA engine operates on chunks of 32 bytes.  We call that
 * a DMACHUNK.
 */

#define DMACHUNK_SHIFT 5
#define DMACHUNK_SIZE (1 << DMACHUNK_SHIFT)
#define BYTES_TO_CHUNKS(bytes) ((bytes) >> DMACHUNK_SHIFT)
#define CHUNKS_TO_BYTES(chunks) ((chunks) << DMACHUNK_SHIFT)

/*
 * Two convenient macros to shift bitfields into/out of position.
 *
 * Observe that (mask & -mask) is (1 << low_set_bit_of(mask)).
 * As long as mask is constant, we trust the compiler will change the
 * multipy and divide into shifts.
 */

#define SHIFT_FIELD(val, mask) (((val) * ((mask) & -(mask))) & (mask))
#define UNSHIFT_FIELD(val, mask) (((val) & (mask)) / ((mask) & -(mask)))

/*
 * dma_chan_desc is invariant information about a Lithium
 * DMA channel.  There are two instances, li_comm1 and li_comm2.
 *
 * Note that the CCTL register fields are write ptr and read ptr, but what
 * we care about are which pointer is updated by software and which by
 * hardware.
 */

typedef struct dma_chan_desc {
        int basereg;
        int cfgreg;
        int ctlreg;
        int hwptrreg;
        int swptrreg;
        int ustreg;
        int mscreg;
        unsigned long swptrmask;
        int ad1843_slot;
        int direction;                  /* LI_CCTL_DIR_IN/OUT */
} dma_chan_desc_t;

static const dma_chan_desc_t li_comm1 = {
        LI_COMM1_BASE,                  /* base register offset */
        LI_COMM1_CFG,                   /* config register offset */
        LI_COMM1_CTL,                   /* control register offset */
        LI_COMM1_CTL + 0,               /* hw ptr reg offset (write ptr) */
        LI_COMM1_CTL + 1,               /* sw ptr reg offset (read ptr) */
        LI_AUDIO1_UST,                  /* ust reg offset */
        LI_AUDIO1_MSC,                  /* msc reg offset */
        LI_CCTL_RPTR,                   /* sw ptr bitmask in ctlval */
        2,                              /* ad1843 serial slot */
        LI_CCFG_DIR_IN                  /* direction */
};

static const dma_chan_desc_t li_comm2 = {
        LI_COMM2_BASE,                  /* base register offset */
        LI_COMM2_CFG,                   /* config register offset */
        LI_COMM2_CTL,                   /* control register offset */
        LI_COMM2_CTL + 1,               /* hw ptr reg offset (read ptr) */
        LI_COMM2_CTL + 0,               /* sw ptr reg offset (writr ptr) */
        LI_AUDIO2_UST,                  /* ust reg offset */
        LI_AUDIO2_MSC,                  /* msc reg offset */
        LI_CCTL_WPTR,                   /* sw ptr bitmask in ctlval */
        2,                              /* ad1843 serial slot */
        LI_CCFG_DIR_OUT                 /* direction */
};

/*
 * dma_chan is variable information about a Lithium DMA channel.
 *
 * The desc field points to invariant information.
 * The lith field points to a lithium_t which is passed
 * to li_read* and li_write* to access the registers.
 * The *val fields shadow the lithium registers' contents.
 */

typedef struct dma_chan {
        const dma_chan_desc_t *desc;
        lithium_t      *lith;
        unsigned long   baseval;
        unsigned long   cfgval;
        unsigned long   ctlval;
} dma_chan_t;

/*
 * ustmsc is a UST/MSC pair (Unadjusted System Time/Media Stream Counter).
 * UST is time in microseconds since the system booted, and MSC is a
 * counter that increments with every audio sample.
 */

typedef struct ustmsc {
        unsigned long long ust;
        unsigned long msc;
} ustmsc_t;

/*
 * li_ad1843_wait waits until lithium says the AD1843 register
 * exchange is not busy.  Returns 0 on success, -EBUSY on timeout.
 *
 * Locking: must be called with lithium_lock held.
 */

static int li_ad1843_wait(lithium_t *lith)
{
        unsigned long later = jiffies + 2;
        while (li_readl(lith, LI_CODEC_COMMAND) & LI_CC_BUSY)
                if (time_after_eq(jiffies, later))
                        return -EBUSY;
        return 0;
}

/*
 * li_read_ad1843_reg returns the current contents of a 16 bit AD1843 register.
 *
 * Returns unsigned register value on success, -errno on failure.
 */

static int li_read_ad1843_reg(lithium_t *lith, int reg)
{
        int val;

        ASSERT(!in_interrupt());
        spin_lock(&lith->lock);
        {
                val = li_ad1843_wait(lith);
                if (val == 0) {
                        li_writel(lith, LI_CODEC_COMMAND, LI_CC_DIR_RD | reg);
                        val = li_ad1843_wait(lith);
                }
                if (val == 0)
                        val = li_readl(lith, LI_CODEC_DATA);
        }
        spin_unlock(&lith->lock);

        DBGXV("li_read_ad1843_reg(lith=0x%p, reg=%d) returns 0x%04x\n",
              lith, reg, val);

        return val;
}

/*
 * li_write_ad1843_reg writes the specified value to a 16 bit AD1843 register.
 */

static void li_write_ad1843_reg(lithium_t *lith, int reg, int newval)
{
        spin_lock(&lith->lock);
        {
                if (li_ad1843_wait(lith) == 0) {
                        li_writel(lith, LI_CODEC_DATA, newval);
                        li_writel(lith, LI_CODEC_COMMAND, LI_CC_DIR_WR | reg);
                }
        }
        spin_unlock(&lith->lock);
}

/*
 * li_setup_dma calculates all the register settings for DMA in a particular
 * mode.  It takes too many arguments.
 */

static void li_setup_dma(dma_chan_t *chan,
                         const dma_chan_desc_t *desc,
                         lithium_t *lith,
                         unsigned long buffer_paddr,
                         int bufshift,
                         int fragshift,
                         int channels,
                         int sampsize)
{
        unsigned long mode, format;
        unsigned long size, tmask;

        DBGEV("(chan=0x%p, desc=0x%p, lith=0x%p, buffer_paddr=0x%lx, "
             "bufshift=%d, fragshift=%d, channels=%d, sampsize=%d)\n",
             chan, desc, lith, buffer_paddr,
             bufshift, fragshift, channels, sampsize);

        /* Reset the channel first. */

        li_writel(lith, desc->ctlreg, LI_CCTL_RESET);

        ASSERT(channels == 1 || channels == 2);
        if (channels == 2)
                mode = LI_CCFG_MODE_STEREO;
        else
                mode = LI_CCFG_MODE_MONO;
        ASSERT(sampsize == 1 || sampsize == 2);
        if (sampsize == 2)
                format = LI_CCFG_FMT_16BIT;
        else
                format = LI_CCFG_FMT_8BIT;
        chan->desc = desc;
        chan->lith = lith;

        /*
         * Lithium DMA address register takes a 40-bit physical
         * address, right-shifted by 8 so it fits in 32 bits.  Bit 37
         * must be set -- it enables cache coherence.
         */

        ASSERT(!(buffer_paddr & 0xFF));
        chan->baseval = (buffer_paddr >> 8) | 1 << (37 - 8);

        chan->cfgval = (!LI_CCFG_LOCK |
                        SHIFT_FIELD(desc->ad1843_slot, LI_CCFG_SLOT) |
                        desc->direction |
                        mode |
                        format);

        size = bufshift - 6;
        tmask = 13 - fragshift;         /* See Lithium DMA Notes above. */
        ASSERT(size >= 2 && size <= 7);
        ASSERT(tmask >= 1 && tmask <= 7);
        chan->ctlval = (!LI_CCTL_RESET |
                        SHIFT_FIELD(size, LI_CCTL_SIZE) |
                        !LI_CCTL_DMA_ENABLE |
                        SHIFT_FIELD(tmask, LI_CCTL_TMASK) |
                        SHIFT_FIELD(0, LI_CCTL_TPTR));

        DBGPV("basereg 0x%x = 0x%lx\n", desc->basereg, chan->baseval);
        DBGPV("cfgreg 0x%x = 0x%lx\n", desc->cfgreg, chan->cfgval);
        DBGPV("ctlreg 0x%x = 0x%lx\n", desc->ctlreg, chan->ctlval);

        li_writel(lith, desc->basereg, chan->baseval);
        li_writel(lith, desc->cfgreg, chan->cfgval);
        li_writel(lith, desc->ctlreg, chan->ctlval);

        DBGRV();
}

static void li_shutdown_dma(dma_chan_t *chan)
{
        lithium_t *lith = chan->lith;
        void * lith1 = lith->page1;

        DBGEV("(chan=0x%p)\n", chan);
        
        chan->ctlval &= ~LI_CCTL_DMA_ENABLE;
        DBGPV("ctlreg 0x%x = 0x%lx\n", chan->desc->ctlreg, chan->ctlval);
        li_writel(lith, chan->desc->ctlreg, chan->ctlval);

        /*
         * Offset 0x500 on Lithium page 1 is an undocumented,
         * unsupported register that holds the zero sample value.
         * Lithium is supposed to output zero samples when DMA is
         * inactive, and repeat the last sample when DMA underflows.
         * But it has a bug, where, after underflow occurs, the zero
         * sample is not reset.
         *
         * I expect this to break in a future rev of Lithium.
         */

        if (lith1 && chan->desc->direction == LI_CCFG_DIR_OUT)
                * (volatile unsigned long *) (lith1 + 0x500) = 0;
}

/*
 * li_activate_dma always starts dma at the beginning of the buffer.
 *
 * N.B., these may be called from interrupt.
 */

static __inline__ void li_activate_dma(dma_chan_t *chan)
{
        chan->ctlval |= LI_CCTL_DMA_ENABLE;
        DBGPV("ctlval = 0x%lx\n", chan->ctlval);
        li_writel(chan->lith, chan->desc->ctlreg, chan->ctlval);
}

static void li_deactivate_dma(dma_chan_t *chan)
{
        lithium_t *lith = chan->lith;
        void * lith2 = lith->page2;

        chan->ctlval &= ~(LI_CCTL_DMA_ENABLE | LI_CCTL_RPTR | LI_CCTL_WPTR);
        DBGPV("ctlval = 0x%lx\n", chan->ctlval);
        DBGPV("ctlreg 0x%x = 0x%lx\n", chan->desc->ctlreg, chan->ctlval);
        li_writel(lith, chan->desc->ctlreg, chan->ctlval);

        /*
         * Offsets 0x98 and 0x9C on Lithium page 2 are undocumented,
         * unsupported registers that are internal copies of the DMA
         * read and write pointers.  Because of a Lithium bug, these
         * registers aren't zeroed correctly when DMA is shut off.  So
         * we whack them directly.
         *
         * I expect this to break in a future rev of Lithium.
         */

        if (lith2 && chan->desc->direction == LI_CCFG_DIR_OUT) {
                * (volatile unsigned long *) (lith2 + 0x98) = 0;
                * (volatile unsigned long *) (lith2 + 0x9C) = 0;
        }
}

/*
 * read/write the ring buffer pointers.  These routines' arguments and results
 * are byte offsets from the beginning of the ring buffer.
 */

static __inline__ int li_read_swptr(dma_chan_t *chan)
{
        const unsigned long mask = chan->desc->swptrmask;

        return CHUNKS_TO_BYTES(UNSHIFT_FIELD(chan->ctlval, mask));
}

static __inline__ int li_read_hwptr(dma_chan_t *chan)
{
        return CHUNKS_TO_BYTES(li_readb(chan->lith, chan->desc->hwptrreg));
}

static __inline__ void li_write_swptr(dma_chan_t *chan, int val)
{
        const unsigned long mask = chan->desc->swptrmask;

        ASSERT(!(val & ~CHUNKS_TO_BYTES(0xFF)));
        val = BYTES_TO_CHUNKS(val);
        chan->ctlval = (chan->ctlval & ~mask) | SHIFT_FIELD(val, mask);
        li_writeb(chan->lith, chan->desc->swptrreg, val);
}

/* li_read_USTMSC() returns a UST/MSC pair for the given channel. */

static void li_read_USTMSC(dma_chan_t *chan, ustmsc_t *ustmsc)
{
        lithium_t *lith = chan->lith;
        const dma_chan_desc_t *desc = chan->desc;
        unsigned long now_low, now_high0, now_high1, chan_ust;

        spin_lock(&lith->lock);
        {
                /*
                 * retry until we do all five reads without the
                 * high word changing.  (High word increments
                 * every 2^32 microseconds, i.e., not often)
                 */
                do {
                        now_high0 = li_readl(lith, LI_UST_HIGH);
                        now_low = li_readl(lith, LI_UST_LOW);

                        /*
                         * Lithium guarantees these two reads will be
                         * atomic -- ust will not increment after msc
                         * is read.
                         */

                        ustmsc->msc = li_readl(lith, desc->mscreg);
                        chan_ust = li_readl(lith, desc->ustreg);

                        now_high1 = li_readl(lith, LI_UST_HIGH);
                } while (now_high0 != now_high1);
        }       
        spin_unlock(&lith->lock);
        ustmsc->ust = ((unsigned long long) now_high0 << 32 | chan_ust);
}

static void li_enable_interrupts(lithium_t *lith, unsigned int mask)
{
        DBGEV("(lith=0x%p, mask=0x%x)\n", lith, mask);

        /* clear any already-pending interrupts. */

        li_writel(lith, LI_INTR_STATUS, mask);

        /* enable the interrupts. */

        mask |= li_readl(lith, LI_INTR_MASK);
        li_writel(lith, LI_INTR_MASK, mask);
}

static void li_disable_interrupts(lithium_t *lith, unsigned int mask)
{
        unsigned int keepmask;

        DBGEV("(lith=0x%p, mask=0x%x)\n", lith, mask);

        /* disable the interrupts */

        keepmask = li_readl(lith, LI_INTR_MASK) & ~mask;
        li_writel(lith, LI_INTR_MASK, keepmask);

        /* clear any pending interrupts. */

        li_writel(lith, LI_INTR_STATUS, mask);
}

/* Get the interrupt status and clear all pending interrupts. */

static unsigned int li_get_clear_intr_status(lithium_t *lith)
{
        unsigned int status;

        status = li_readl(lith, LI_INTR_STATUS);
        li_writel(lith, LI_INTR_STATUS, ~0);
        return status & li_readl(lith, LI_INTR_MASK);
}

static int li_init(lithium_t *lith)
{
        /* 1. System power supplies stabilize. */

        /* 2. Assert the ~RESET signal. */

        li_writel(lith, LI_HOST_CONTROLLER, LI_HC_RESET);
        udelay(1);

        /* 3. Deassert the ~RESET signal and enter a wait period to allow
           the AD1843 internal clocks and the external crystal oscillator
           to stabilize. */

        li_writel(lith, LI_HOST_CONTROLLER, LI_HC_LINK_ENABLE);
        udelay(1);

        return 0;
}

/*****************************************************************************/
/* AD1843 access */

/*
 * AD1843 bitfield definitions.  All are named as in the AD1843 data
 * sheet, with ad1843_ prepended and individual bit numbers removed.
 *
 * E.g., bits LSS0 through LSS2 become ad1843_LSS.
 *
 * Only the bitfields we need are defined.
 */

typedef struct ad1843_bitfield {
        char reg;
        char lo_bit;
        char nbits;
} ad1843_bitfield_t;

static const ad1843_bitfield_t
        ad1843_PDNO   = {  0, 14,  1 }, /* Converter Power-Down Flag */
        ad1843_INIT   = {  0, 15,  1 }, /* Clock Initialization Flag */
        ad1843_RIG    = {  2,  0,  4 }, /* Right ADC Input Gain */
        ad1843_RMGE   = {  2,  4,  1 }, /* Right ADC Mic Gain Enable */
        ad1843_RSS    = {  2,  5,  3 }, /* Right ADC Source Select */
        ad1843_LIG    = {  2,  8,  4 }, /* Left ADC Input Gain */
        ad1843_LMGE   = {  2, 12,  1 }, /* Left ADC Mic Gain Enable */
        ad1843_LSS    = {  2, 13,  3 }, /* Left ADC Source Select */
        ad1843_RX1M   = {  4,  0,  5 }, /* Right Aux 1 Mix Gain/Atten */
        ad1843_RX1MM  = {  4,  7,  1 }, /* Right Aux 1 Mix Mute */
        ad1843_LX1M   = {  4,  8,  5 }, /* Left Aux 1 Mix Gain/Atten */
        ad1843_LX1MM  = {  4, 15,  1 }, /* Left Aux 1 Mix Mute */
        ad1843_RX2M   = {  5,  0,  5 }, /* Right Aux 2 Mix Gain/Atten */
        ad1843_RX2MM  = {  5,  7,  1 }, /* Right Aux 2 Mix Mute */
        ad1843_LX2M   = {  5,  8,  5 }, /* Left Aux 2 Mix Gain/Atten */
        ad1843_LX2MM  = {  5, 15,  1 }, /* Left Aux 2 Mix Mute */
        ad1843_RMCM   = {  7,  0,  5 }, /* Right Mic Mix Gain/Atten */
        ad1843_RMCMM  = {  7,  7,  1 }, /* Right Mic Mix Mute */
        ad1843_LMCM   = {  7,  8,  5 }, /* Left Mic Mix Gain/Atten */
        ad1843_LMCMM  = {  7, 15,  1 }, /* Left Mic Mix Mute */
        ad1843_HPOS   = {  8,  4,  1 }, /* Headphone Output Voltage Swing */
        ad1843_HPOM   = {  8,  5,  1 }, /* Headphone Output Mute */
        ad1843_RDA1G  = {  9,  0,  6 }, /* Right DAC1 Analog/Digital Gain */
        ad1843_RDA1GM = {  9,  7,  1 }, /* Right DAC1 Analog Mute */
        ad1843_LDA1G  = {  9,  8,  6 }, /* Left DAC1 Analog/Digital Gain */
        ad1843_LDA1GM = {  9, 15,  1 }, /* Left DAC1 Analog Mute */
        ad1843_RDA1AM = { 11,  7,  1 }, /* Right DAC1 Digital Mute */
        ad1843_LDA1AM = { 11, 15,  1 }, /* Left DAC1 Digital Mute */
        ad1843_ADLC   = { 15,  0,  2 }, /* ADC Left Sample Rate Source */
        ad1843_ADRC   = { 15,  2,  2 }, /* ADC Right Sample Rate Source */
        ad1843_DA1C   = { 15,  8,  2 }, /* DAC1 Sample Rate Source */
        ad1843_C1C    = { 17,  0, 16 }, /* Clock 1 Sample Rate Select */
        ad1843_C2C    = { 20,  0, 16 }, /* Clock 1 Sample Rate Select */
        ad1843_DAADL  = { 25,  4,  2 }, /* Digital ADC Left Source Select */
        ad1843_DAADR  = { 25,  6,  2 }, /* Digital ADC Right Source Select */
        ad1843_DRSFLT = { 25, 15,  1 }, /* Digital Reampler Filter Mode */
        ad1843_ADLF   = { 26,  0,  2 }, /* ADC Left Channel Data Format */
        ad1843_ADRF   = { 26,  2,  2 }, /* ADC Right Channel Data Format */
        ad1843_ADTLK  = { 26,  4,  1 }, /* ADC Transmit Lock Mode Select */
        ad1843_SCF    = { 26,  7,  1 }, /* SCLK Frequency Select */
        ad1843_DA1F   = { 26,  8,  2 }, /* DAC1 Data Format Select */
        ad1843_DA1SM  = { 26, 14,  1 }, /* DAC1 Stereo/Mono Mode Select */
        ad1843_ADLEN  = { 27,  0,  1 }, /* ADC Left Channel Enable */
        ad1843_ADREN  = { 27,  1,  1 }, /* ADC Right Channel Enable */
        ad1843_AAMEN  = { 27,  4,  1 }, /* Analog to Analog Mix Enable */
        ad1843_ANAEN  = { 27,  7,  1 }, /* Analog Channel Enable */
        ad1843_DA1EN  = { 27,  8,  1 }, /* DAC1 Enable */
        ad1843_DA2EN  = { 27,  9,  1 }, /* DAC2 Enable */
        ad1843_C1EN   = { 28, 11,  1 }, /* Clock Generator 1 Enable */
        ad1843_C2EN   = { 28, 12,  1 }, /* Clock Generator 2 Enable */
        ad1843_PDNI   = { 28, 15,  1 }; /* Converter Power Down */

/*
 * The various registers of the AD1843 use three different formats for
 * specifying gain.  The ad1843_gain structure parameterizes the
 * formats.
 */

typedef struct ad1843_gain {

        int     negative;               /* nonzero if gain is negative. */
        const ad1843_bitfield_t *lfield;
        const ad1843_bitfield_t *rfield;

} ad1843_gain_t;

static const ad1843_gain_t ad1843_gain_RECLEV
                                = { 0, &ad1843_LIG,   &ad1843_RIG };
static const ad1843_gain_t ad1843_gain_LINE
                                = { 1, &ad1843_LX1M,  &ad1843_RX1M };
static const ad1843_gain_t ad1843_gain_CD
                                = { 1, &ad1843_LX2M,  &ad1843_RX2M };
static const ad1843_gain_t ad1843_gain_MIC
                                = { 1, &ad1843_LMCM,  &ad1843_RMCM };
static const ad1843_gain_t ad1843_gain_PCM
                                = { 1, &ad1843_LDA1G, &ad1843_RDA1G };

/* read the current value of an AD1843 bitfield. */

static int ad1843_read_bits(lithium_t *lith, const ad1843_bitfield_t *field)
{
        int w = li_read_ad1843_reg(lith, field->reg);
        int val = w >> field->lo_bit & ((1 << field->nbits) - 1);

        DBGXV("ad1843_read_bits(lith=0x%p, field->{%d %d %d}) returns 0x%x\n",
              lith, field->reg, field->lo_bit, field->nbits, val);

        return val;
}

/*
 * write a new value to an AD1843 bitfield and return the old value.
 */

static int ad1843_write_bits(lithium_t *lith,
                             const ad1843_bitfield_t *field,
                             int newval)
{
        int w = li_read_ad1843_reg(lith, field->reg);
        int mask = ((1 << field->nbits) - 1) << field->lo_bit;
        int oldval = (w & mask) >> field->lo_bit;
        int newbits = (newval << field->lo_bit) & mask;
        w = (w & ~mask) | newbits;
        (void) li_write_ad1843_reg(lith, field->reg, w);

        DBGXV("ad1843_write_bits(lith=0x%p, field->{%d %d %d}, val=0x%x) "
              "returns 0x%x\n",
              lith, field->reg, field->lo_bit, field->nbits, newval,
              oldval);

        return oldval;
}

/*
 * ad1843_read_multi reads multiple bitfields from the same AD1843
 * register.  It uses a single read cycle to do it.  (Reading the
 * ad1843 requires 256 bit times at 12.288 MHz, or nearly 20
 * microseconds.)
 *
 * Called ike this.
 *
 *  ad1843_read_multi(lith, nfields,
 *                    &ad1843_FIELD1, &val1,
 *                    &ad1843_FIELD2, &val2, ...);
 */

static void ad1843_read_multi(lithium_t *lith, int argcount, ...)
{
        va_list ap;
        const ad1843_bitfield_t *fp;
        int w = 0, mask, *value, reg = -1;

        va_start(ap, argcount);
        while (--argcount >= 0) {
                fp = va_arg(ap, const ad1843_bitfield_t *);
                value = va_arg(ap, int *);
                if (reg == -1) {
                        reg = fp->reg;
                        w = li_read_ad1843_reg(lith, reg);
                }
                ASSERT(reg == fp->reg);
                mask = (1 << fp->nbits) - 1;
                *value = w >> fp->lo_bit & mask;
        }
        va_end(ap);
}

/*
 * ad1843_write_multi stores multiple bitfields into the same AD1843
 * register.  It uses one read and one write cycle to do it.
 *
 * Called like this.
 *
 *  ad1843_write_multi(lith, nfields,
 *                     &ad1843_FIELD1, val1,
 *                     &ad1843_FIELF2, val2, ...);
 */

static void ad1843_write_multi(lithium_t *lith, int argcount, ...)
{
        va_list ap;
        int reg;
        const ad1843_bitfield_t *fp;
        int value;
        int w, m, mask, bits;

        mask = 0;
        bits = 0;
        reg = -1;

        va_start(ap, argcount);
        while (--argcount >= 0) {
                fp = va_arg(ap, const ad1843_bitfield_t *);
                value = va_arg(ap, int);
                if (reg == -1)
                        reg = fp->reg;
                ASSERT(fp->reg == reg);
                m = ((1 << fp->nbits) - 1) << fp->lo_bit;
                mask |= m;
                bits |= (value << fp->lo_bit) & m;
        }
        va_end(ap);
        ASSERT(!(bits & ~mask));
        if (~mask & 0xFFFF)
                w = li_read_ad1843_reg(lith, reg);
        else
                w = 0;
        w = (w & ~mask) | bits;
        (void) li_write_ad1843_reg(lith, reg, w);
}

/*
 * ad1843_get_gain reads the specified register and extracts the gain value
 * using the supplied gain type.  It returns the gain in OSS format.
 */

static int ad1843_get_gain(lithium_t *lith, const ad1843_gain_t *gp)
{
        int lg, rg;
        unsigned short mask = (1 << gp->lfield->nbits) - 1;

        ad1843_read_multi(lith, 2, gp->lfield, &lg, gp->rfield, &rg);
        if (gp->negative) {
                lg = mask - lg;
                rg = mask - rg;
        }
        lg = (lg * 100 + (mask >> 1)) / mask;
        rg = (rg * 100 + (mask >> 1)) / mask;
        return lg << 0 | rg << 8;
}

/*
 * Set an audio channel's gain. Converts from OSS format to AD1843's
 * format.
 *
 * Returns the new gain, which may be lower than the old gain.
 */

static int ad1843_set_gain(lithium_t *lith,
                           const ad1843_gain_t *gp,
                           int newval)
{
        unsigned short mask = (1 << gp->lfield->nbits) - 1;

        int lg = newval >> 0 & 0xFF;
        int rg = newval >> 8;
        if (lg < 0 || lg > 100 || rg < 0 || rg > 100)
                return -EINVAL;
        lg = (lg * mask + (mask >> 1)) / 100;
        rg = (rg * mask + (mask >> 1)) / 100;
        if (gp->negative) {
                lg = mask - lg;
                rg = mask - rg;
        }
        ad1843_write_multi(lith, 2, gp->lfield, lg, gp->rfield, rg);
        return ad1843_get_gain(lith, gp);
}

/* Returns the current recording source, in OSS format. */

static int ad1843_get_recsrc(lithium_t *lith)
{
        int ls = ad1843_read_bits(lith, &ad1843_LSS);

        switch (ls) {
        case 1:
                return SOUND_MASK_MIC;
        case 2:
                return SOUND_MASK_LINE;
        case 3:
                return SOUND_MASK_CD;
        case 6:
                return SOUND_MASK_PCM;
        default:
                ASSERT(0);
                return -1;
        }
}

/*
 * Enable/disable digital resample mode in the AD1843.
 *
 * The AD1843 requires that ADL, ADR, DA1 and DA2 be powered down
 * while switching modes.  So we save DA1's state (DA2's state is not
 * interesting), power them down, switch into/out of resample mode,
 * power them up, and restore state.
 *
 * This will cause audible glitches if D/A or A/D is going on, so the
 * driver disallows that (in mixer_write_ioctl()).
 *
 * The open question is, is this worth doing?  I'm leaving it in,
 * because it's written, but...
 */

static void ad1843_set_resample_mode(lithium_t *lith, int onoff)
{
        /* Save DA1 mute and gain (addr 9 is DA1 analog gain/attenuation) */
        int save_da1 = li_read_ad1843_reg(lith, 9);

        /* Power down A/D and D/A. */
        ad1843_write_multi(lith, 4,
                           &ad1843_DA1EN, 0,
                           &ad1843_DA2EN, 0,
                           &ad1843_ADLEN, 0,
                           &ad1843_ADREN, 0);

        /* Switch mode */
        ASSERT(onoff == 0 || onoff == 1);
        ad1843_write_bits(lith, &ad1843_DRSFLT, onoff);

        /* Power up A/D and D/A. */
        ad1843_write_multi(lith, 3,
                           &ad1843_DA1EN, 1,
                           &ad1843_ADLEN, 1,
                           &ad1843_ADREN, 1);

        /* Restore DA1 mute and gain. */
        li_write_ad1843_reg(lith, 9, save_da1);
}

/*
 * Set recording source.  Arg newsrc specifies an OSS channel mask.
 *
 * The complication is that when we switch into/out of loopback mode
 * (i.e., src = SOUND_MASK_PCM), we change the AD1843 into/out of
 * digital resampling mode.
 *
 * Returns newsrc on success, -errno on failure.
 */

static int ad1843_set_recsrc(lithium_t *lith, int newsrc)
{
        int bits;
        int oldbits;

        switch (newsrc) {
        case SOUND_MASK_PCM:
                bits = 6;
                break;

        case SOUND_MASK_MIC:
                bits = 1;
                break;

        case SOUND_MASK_LINE:
                bits = 2;
                break;

        case SOUND_MASK_CD:
                bits = 3;
                break;

        default:
                return -EINVAL;
        }
        oldbits = ad1843_read_bits(lith, &ad1843_LSS);
        if (newsrc == SOUND_MASK_PCM && oldbits != 6) {
                DBGP("enabling digital resample mode\n");
                ad1843_set_resample_mode(lith, 1);
                ad1843_write_multi(lith, 2,
                                   &ad1843_DAADL, 2,
                                   &ad1843_DAADR, 2);
        } else if (newsrc != SOUND_MASK_PCM && oldbits == 6) {
                DBGP("disabling digital resample mode\n");
                ad1843_set_resample_mode(lith, 0);
                ad1843_write_multi(lith, 2,
                                   &ad1843_DAADL, 0,
                                   &ad1843_DAADR, 0);
        }
        ad1843_write_multi(lith, 2, &ad1843_LSS, bits, &ad1843_RSS, bits);
        return newsrc;
}

/*
 * Return current output sources, in OSS format.
 */

static int ad1843_get_outsrc(lithium_t *lith)
{
        int pcm, line, mic, cd;

        pcm  = ad1843_read_bits(lith, &ad1843_LDA1GM) ? 0 : SOUND_MASK_PCM;
        line = ad1843_read_bits(lith, &ad1843_LX1MM)  ? 0 : SOUND_MASK_LINE;
        cd   = ad1843_read_bits(lith, &ad1843_LX2MM)  ? 0 : SOUND_MASK_CD;
        mic  = ad1843_read_bits(lith, &ad1843_LMCMM)  ? 0 : SOUND_MASK_MIC;

        return pcm | line | cd | mic;
}

/*
 * Set output sources.  Arg is a mask of active sources in OSS format.
 *
 * Returns source mask on success, -errno on failure.
 */

static int ad1843_set_outsrc(lithium_t *lith, int mask)
{
        int pcm, line, mic, cd;

        if (mask & ~(SOUND_MASK_PCM | SOUND_MASK_LINE |
                     SOUND_MASK_CD | SOUND_MASK_MIC))
                return -EINVAL;
        pcm  = (mask & SOUND_MASK_PCM)  ? 0 : 1;
        line = (mask & SOUND_MASK_LINE) ? 0 : 1;
        mic  = (mask & SOUND_MASK_MIC)  ? 0 : 1;
        cd   = (mask & SOUND_MASK_CD)   ? 0 : 1;

        ad1843_write_multi(lith, 2, &ad1843_LDA1GM, pcm, &ad1843_RDA1GM, pcm);
        ad1843_write_multi(lith, 2, &ad1843_LX1MM, line, &ad1843_RX1MM, line);
        ad1843_write_multi(lith, 2, &ad1843_LX2MM, cd,   &ad1843_RX2MM, cd);
        ad1843_write_multi(lith, 2, &ad1843_LMCMM, mic,  &ad1843_RMCMM, mic);

        return mask;
}

/* Setup ad1843 for D/A conversion. */

static void ad1843_setup_dac(lithium_t *lith,
                             int framerate,
                             int fmt,
                             int channels)
{
        int ad_fmt = 0, ad_mode = 0;

        DBGEV("(lith=0x%p, framerate=%d, fmt=%d, channels=%d)\n",
              lith, framerate, fmt, channels);

        switch (fmt) {
        case AFMT_S8:           ad_fmt = 1; break;
        case AFMT_U8:           ad_fmt = 1; break;
        case AFMT_S16_LE:       ad_fmt = 1; break;
        case AFMT_MU_LAW:       ad_fmt = 2; break;
        case AFMT_A_LAW:        ad_fmt = 3; break;
        default:                ASSERT(0);
        }

        switch (channels) {
        case 2:                 ad_mode = 0; break;
        case 1:                 ad_mode = 1; break;
        default:                ASSERT(0);
        }
                
        DBGPV("ad_mode = %d, ad_fmt = %d\n", ad_mode, ad_fmt);
        ASSERT(framerate >= 4000 && framerate <= 49000);
        ad1843_write_bits(lith, &ad1843_C1C, framerate);
        ad1843_write_multi(lith, 2,
                           &ad1843_DA1SM, ad_mode, &ad1843_DA1F, ad_fmt);
}

static void ad1843_shutdown_dac(lithium_t *lith)
{
        ad1843_write_bits(lith, &ad1843_DA1F, 1);
}

static void ad1843_setup_adc(lithium_t *lith, int framerate, int fmt, int channels)
{
        int da_fmt = 0;

        DBGEV("(lith=0x%p, framerate=%d, fmt=%d, channels=%d)\n",
              lith, framerate, fmt, channels);

        switch (fmt) {
        case AFMT_S8:           da_fmt = 1; break;
        case AFMT_U8:           da_fmt = 1; break;
        case AFMT_S16_LE:       da_fmt = 1; break;
        case AFMT_MU_LAW:       da_fmt = 2; break;
        case AFMT_A_LAW:        da_fmt = 3; break;
        default:                ASSERT(0);
        }

        DBGPV("da_fmt = %d\n", da_fmt);
        ASSERT(framerate >= 4000 && framerate <= 49000);
        ad1843_write_bits(lith, &ad1843_C2C, framerate);
        ad1843_write_multi(lith, 2,
                           &ad1843_ADLF, da_fmt, &ad1843_ADRF, da_fmt);
}

static void ad1843_shutdown_adc(lithium_t *lith)
{
        /* nothing to do */
}

/*
 * Fully initialize the ad1843.  As described in the AD1843 data
 * sheet, section "START-UP SEQUENCE".  The numbered comments are
 * subsection headings from the data sheet.  See the data sheet, pages
 * 52-54, for more info.
 *
 * return 0 on success, -errno on failure.  */

static int __init ad1843_init(lithium_t *lith)
{
        unsigned long later;
        int err;

        err = li_init(lith);
        if (err)
                return err;

        if (ad1843_read_bits(lith, &ad1843_INIT) != 0) {
                printk(KERN_ERR "vwsnd sound: AD1843 won't initialize\n");
                return -EIO;
        }

        ad1843_write_bits(lith, &ad1843_SCF, 1);

        /* 4. Put the conversion resources into standby. */

        ad1843_write_bits(lith, &ad1843_PDNI, 0);
        later = jiffies + HZ / 2;       /* roughly half a second */
        DBGDO(shut_up++);
        while (ad1843_read_bits(lith, &ad1843_PDNO)) {
                if (time_after(jiffies, later)) {
                        printk(KERN_ERR
                               "vwsnd audio: AD1843 won't power up\n");
                        return -EIO;
                }
                schedule();
        }
        DBGDO(shut_up--);

        /* 5. Power up the clock generators and enable clock output pins. */

        ad1843_write_multi(lith, 2, &ad1843_C1EN, 1, &ad1843_C2EN, 1);

        /* 6. Configure conversion resources while they are in standby. */

        /* DAC1 uses clock 1 as source, ADC uses clock 2.  Always. */

        ad1843_write_multi(lith, 3,
                           &ad1843_DA1C, 1,
                           &ad1843_ADLC, 2,
                           &ad1843_ADRC, 2);

        /* 7. Enable conversion resources. */

        ad1843_write_bits(lith, &ad1843_ADTLK, 1);
        ad1843_write_multi(lith, 5,
                           &ad1843_ANAEN, 1,
                           &ad1843_AAMEN, 1,
                           &ad1843_DA1EN, 1,
                           &ad1843_ADLEN, 1,
                           &ad1843_ADREN, 1);

        /* 8. Configure conversion resources while they are enabled. */

        ad1843_write_bits(lith, &ad1843_DA1C, 1);

        /* Unmute all channels. */

        ad1843_set_outsrc(lith,
                          (SOUND_MASK_PCM | SOUND_MASK_LINE |
                           SOUND_MASK_MIC | SOUND_MASK_CD));
        ad1843_write_multi(lith, 2, &ad1843_LDA1AM, 0, &ad1843_RDA1AM, 0);

        /* Set default recording source to Line In and set
         * mic gain to +20 dB.
         */

        ad1843_set_recsrc(lith, SOUND_MASK_LINE);
        ad1843_write_multi(lith, 2, &ad1843_LMGE, 1, &ad1843_RMGE, 1);

        /* Set Speaker Out level to +/- 4V and unmute it. */

        ad1843_write_multi(lith, 2, &ad1843_HPOS, 1, &ad1843_HPOM, 0);

        return 0;
}

/*****************************************************************************/
/* PCM I/O */

#define READ_INTR_MASK  (LI_INTR_COMM1_TRIG | LI_INTR_COMM1_OVERFLOW)
#define WRITE_INTR_MASK (LI_INTR_COMM2_TRIG | LI_INTR_COMM2_UNDERFLOW)

typedef enum vwsnd_port_swstate {       /* software state */
        SW_OFF,
        SW_INITIAL,
        SW_RUN,
        SW_DRAIN,
} vwsnd_port_swstate_t;

typedef enum vwsnd_port_hwstate {       /* hardware state */
        HW_STOPPED,
        HW_RUNNING,
} vwsnd_port_hwstate_t;

/*
 * These flags are read by ISR, but only written at baseline.
 */

typedef enum vwsnd_port_flags {
        DISABLED = 1 << 0,
        ERFLOWN  = 1 << 1,              /* overflown or underflown */
        HW_BUSY  = 1 << 2,
} vwsnd_port_flags_t;

/*
 * vwsnd_port is the per-port data structure.  Each device has two
 * ports, one for input and one for output.
 *
 * Locking:
 *
 *      port->lock protects: hwstate, flags, swb_[iu]_avail.
 *
 *      devc->io_mutex protects: swstate, sw_*, swb_[iu]_idx.
 *
 *      everything else is only written by open/release or
 *      pcm_{setup,shutdown}(), which are serialized by a
 *      combination of devc->open_mutex and devc->io_mutex.
 */

typedef struct vwsnd_port {

        spinlock_t      lock;
        wait_queue_head_t queue;
        vwsnd_port_swstate_t swstate;
        vwsnd_port_hwstate_t hwstate;
        vwsnd_port_flags_t flags;

        int             sw_channels;
        int             sw_samplefmt;
        int             sw_framerate;
        int             sample_size;
        int             frame_size;
        unsigned int    zero_word;      /* zero for the sample format */

        int             sw_fragshift;
        int             sw_fragcount;
        int             sw_subdivshift;

        unsigned int    hw_fragshift;
        unsigned int    hw_fragsize;
        unsigned int    hw_fragcount;

        int             hwbuf_size;
        unsigned long   hwbuf_paddr;
        unsigned long   hwbuf_vaddr;
        void *          hwbuf;          /* hwbuf == hwbuf_vaddr */
        int             hwbuf_max;      /* max bytes to preload */

        void *          swbuf;
        unsigned int    swbuf_size;     /* size in bytes */
        unsigned int    swb_u_idx;      /* index of next user byte */
        unsigned int    swb_i_idx;      /* index of next intr byte */
        unsigned int    swb_u_avail;    /* # bytes avail to user */
        unsigned int    swb_i_avail;    /* # bytes avail to intr */

        dma_chan_t      chan;

        /* Accounting */

        int             byte_count;
        int             frag_count;
        int             MSC_offset;

} vwsnd_port_t;

/* vwsnd_dev is the per-device data structure. */

typedef struct vwsnd_dev {
        struct vwsnd_dev *next_dev;
        int             audio_minor;    /* minor number of audio device */
        int             mixer_minor;    /* minor number of mixer device */

        struct mutex open_mutex;
        struct mutex io_mutex;
        struct mutex mix_mutex;
        mode_t          open_mode;
        wait_queue_head_t open_wait;

        lithium_t       lith;

        vwsnd_port_t    rport;
        vwsnd_port_t    wport;
} vwsnd_dev_t;

static vwsnd_dev_t *vwsnd_dev_list;     /* linked list of all devices */

static atomic_t vwsnd_use_count = ATOMIC_INIT(0);

# define INC_USE_COUNT (atomic_inc(&vwsnd_use_count))
# define DEC_USE_COUNT (atomic_dec(&vwsnd_use_count))
# define IN_USE        (atomic_read(&vwsnd_use_count) != 0)

/*
 * Lithium can only DMA multiples of 32 bytes.  Its DMA buffer may
 * be up to 8 Kb.  This driver always uses 8 Kb.
 *
 * Memory bug workaround -- I'm not sure what's going on here, but
 * somehow pcm_copy_out() was triggering segv's going on to the next
 * page of the hw buffer.  So, I make the hw buffer one size bigger
 * than we actually use.  That way, the following page is allocated
 * and mapped, and no error.  I suspect that something is broken
 * in Cobalt, but haven't really investigated.  HBO is the actual
 * size of the buffer, and HWBUF_ORDER is what we allocate.
 */

#define HWBUF_SHIFT 13
#define HWBUF_SIZE (1 << HWBUF_SHIFT)
# define HBO         (HWBUF_SHIFT > PAGE_SHIFT ? HWBUF_SHIFT - PAGE_SHIFT : 0)
# define HWBUF_ORDER (HBO + 1)          /* next size bigger */
#define MIN_SPEED 4000
#define MAX_SPEED 49000

#define MIN_FRAGSHIFT                   (DMACHUNK_SHIFT + 1)
#define MAX_FRAGSHIFT                   (PAGE_SHIFT)
#define MIN_FRAGSIZE                    (1 << MIN_FRAGSHIFT)
#define MAX_FRAGSIZE                    (1 << MAX_FRAGSHIFT)
#define MIN_FRAGCOUNT(fragsize)         3
#define MAX_FRAGCOUNT(fragsize)         (32 * PAGE_SIZE / (fragsize))
#define DEFAULT_FRAGSHIFT               12
#define DEFAULT_FRAGCOUNT               16
#define DEFAULT_SUBDIVSHIFT             0

/*
 * The software buffer (swbuf) is a ring buffer shared between user
 * level and interrupt level.  Each level owns some of the bytes in
 * the buffer, and may give bytes away by calling swb_inc_{u,i}().
 * User level calls _u for user, and interrupt level calls _i for
 * interrupt.
 *
 * port->swb_{u,i}_avail is the number of bytes available to that level.
 *
 * port->swb_{u,i}_idx is the index of the first available byte in the
 * buffer.
 *
 * Each level calls swb_inc_{u,i}() to atomically increment its index,
 * recalculate the number of bytes available for both sides, and
 * return the number of bytes available.  Since each side can only
 * give away bytes, the other side can only increase the number of
 * bytes available to this side.  Each side updates its own index
 * variable, swb_{u,i}_idx, so no lock is needed to read it.
 *
 * To query the number of bytes available, call swb_inc_{u,i} with an
 * increment of zero.
 */

static __inline__ unsigned int __swb_inc_u(vwsnd_port_t *port, int inc)
{
        if (inc) {
                port->swb_u_idx += inc;
                port->swb_u_idx %= port->swbuf_size;
                port->swb_u_avail -= inc;
                port->swb_i_avail += inc;
        }
        return port->swb_u_avail;
}

static __inline__ unsigned int swb_inc_u(vwsnd_port_t *port, int inc)
{
        unsigned long flags;
        unsigned int ret;

        spin_lock_irqsave(&port->lock, flags);
        {
                ret = __swb_inc_u(port, inc);
        }
        spin_unlock_irqrestore(&port->lock, flags);
        return ret;
}

static __inline__ unsigned int __swb_inc_i(vwsnd_port_t *port, int inc)
{
        if (inc) {
                port->swb_i_idx += inc;
                port->swb_i_idx %= port->swbuf_size;
                port->swb_i_avail -= inc;
                port->swb_u_avail += inc;
        }
        return port->swb_i_avail;
}

static __inline__ unsigned int swb_inc_i(vwsnd_port_t *port, int inc)
{
        unsigned long flags;
        unsigned int ret;

        spin_lock_irqsave(&port->lock, flags);
        {
                ret = __swb_inc_i(port, inc);
        }
        spin_unlock_irqrestore(&port->lock, flags);
        return ret;
}

/*
 * pcm_setup - this routine initializes all port state after
 * mode-setting ioctls have been done, but before the first I/O is
 * done.
 *
 * Locking: called with devc->io_mutex held.
 *
 * Returns 0 on success, -errno on failure.
 */

static int pcm_setup(vwsnd_dev_t *devc,
                     vwsnd_port_t *rport,
                     vwsnd_port_t *wport)
{
        vwsnd_port_t *aport = rport ? rport : wport;
        int sample_size;
        unsigned int zero_word;

        DBGEV("(devc=0x%p, rport=0x%p, wport=0x%p)\n", devc, rport, wport);

        ASSERT(aport != NULL);
        if (aport->swbuf != NULL)
                return 0;
        switch (aport->sw_samplefmt) {
        case AFMT_MU_LAW:
                sample_size = 1;
                zero_word = 0xFFFFFFFF ^ 0x80808080;
                break;

        case AFMT_A_LAW:
                sample_size = 1;
                zero_word = 0xD5D5D5D5 ^ 0x80808080;
                break;

        case AFMT_U8:
                sample_size = 1;
                zero_word = 0x80808080;
                break;

        case AFMT_S8:
                sample_size = 1;
                zero_word = 0x00000000;
                break;

        case AFMT_S16_LE:
                sample_size = 2;
                zero_word = 0x00000000;
                break;

        default:
                sample_size = 0;        /* prevent compiler warning */
                zero_word = 0;
                ASSERT(0);
        }
        aport->sample_size  = sample_size;
        aport->zero_word    = zero_word;
        aport->frame_size   = aport->sw_channels * aport->sample_size;
        aport->hw_fragshift = aport->sw_fragshift - aport->sw_subdivshift;
        aport->hw_fragsize  = 1 << aport->hw_fragshift;
        aport->hw_fragcount = aport->sw_fragcount << aport->sw_subdivshift;
        ASSERT(aport->hw_fragsize >= MIN_FRAGSIZE);
        ASSERT(aport->hw_fragsize <= MAX_FRAGSIZE);
        ASSERT(aport->hw_fragcount >= MIN_FRAGCOUNT(aport->hw_fragsize));
        ASSERT(aport->hw_fragcount <= MAX_FRAGCOUNT(aport->hw_fragsize));
        if (rport) {
                int hwfrags, swfrags;
                rport->hwbuf_max = aport->hwbuf_size - DMACHUNK_SIZE;
                hwfrags = rport->hwbuf_max >> aport->hw_fragshift;
                swfrags = aport->hw_fragcount - hwfrags;
                if (swfrags < 2)
                        swfrags = 2;
                rport->swbuf_size = swfrags * aport->hw_fragsize;
                DBGPV("hwfrags = %d, swfrags = %d\n", hwfrags, swfrags);
                DBGPV("read hwbuf_max = %d, swbuf_size = %d\n",
                     rport->hwbuf_max, rport->swbuf_size);
        }
        if (wport) {
                int hwfrags, swfrags;
                int total_bytes = aport->hw_fragcount * aport->hw_fragsize;
                wport->hwbuf_max = aport->hwbuf_size - DMACHUNK_SIZE;
                if (wport->hwbuf_max > total_bytes)
                        wport->hwbuf_max = total_bytes;
                hwfrags = wport->hwbuf_max >> aport->hw_fragshift;
                DBGPV("hwfrags = %d\n", hwfrags);
                swfrags = aport->hw_fragcount - hwfrags;
                if (swfrags < 2)
                        swfrags = 2;
                wport->swbuf_size = swfrags * aport->hw_fragsize;
                DBGPV("hwfrags = %d, swfrags = %d\n", hwfrags, swfrags);
                DBGPV("write hwbuf_max = %d, swbuf_size = %d\n",
                     wport->hwbuf_max, wport->swbuf_size);
        }

        aport->swb_u_idx    = 0;
        aport->swb_i_idx    = 0;
        aport->byte_count   = 0;

        /*
         * Is this a Cobalt bug?  We need to make this buffer extend
         * one page further than we actually use -- somehow memcpy
         * causes an exceptoin otherwise.  I suspect there's a bug in
         * Cobalt (or somewhere) where it's generating a fault on a
         * speculative load or something.  Obviously, I haven't taken
         * the time to track it down.
         */

        aport->swbuf        = vmalloc(aport->swbuf_size + PAGE_SIZE);
        if (!aport->swbuf)
                return -ENOMEM;
        if (rport && wport) {
                ASSERT(aport == rport);
                ASSERT(wport->swbuf == NULL);
                /* One extra page - see comment above. */
                wport->swbuf = vmalloc(aport->swbuf_size + PAGE_SIZE);
                if (!wport->swbuf) {
                        vfree(aport->swbuf);
                        aport->swbuf = NULL;
                        return -ENOMEM;
                }
                wport->sample_size  = rport->sample_size;
                wport->zero_word    = rport->zero_word;
                wport->frame_size   = rport->frame_size;
                wport->hw_fragshift = rport->hw_fragshift;
                wport->hw_fragsize  = rport->hw_fragsize;
                wport->hw_fragcount = rport->hw_fragcount;
                wport->swbuf_size   = rport->swbuf_size;
                wport->hwbuf_max    = rport->hwbuf_max;
                wport->swb_u_idx    = rport->swb_u_idx;
                wport->swb_i_idx    = rport->swb_i_idx;
                wport->byte_count   = rport->byte_count;
        }
        if (rport) {
                rport->swb_u_avail = 0;
                rport->swb_i_avail = rport->swbuf_size;
                rport->swstate = SW_RUN;
                li_setup_dma(&rport->chan,
                             &li_comm1,
                             &devc->lith,
                             rport->hwbuf_paddr,
                             HWBUF_SHIFT,
                             rport->hw_fragshift,
                             rport->sw_channels,
                             rport->sample_size);
                ad1843_setup_adc(&devc->lith,
                                 rport->sw_framerate,
                                 rport->sw_samplefmt,
                                 rport->sw_channels);
                li_enable_interrupts(&devc->lith, READ_INTR_MASK);
                if (!(rport->flags & DISABLED)) {
                        ustmsc_t ustmsc;
                        rport->hwstate = HW_RUNNING;
                        li_activate_dma(&rport->chan);
                        li_read_USTMSC(&rport->chan, &ustmsc);
                        rport->MSC_offset = ustmsc.msc;
                }
        }
        if (wport) {
                if (wport->hwbuf_max > wport->swbuf_size)
                        wport->hwbuf_max = wport->swbuf_size;
                wport->flags &= ~ERFLOWN;
                wport->swb_u_avail = wport->swbuf_size;
                wport->swb_i_avail = 0;
                wport->swstate = SW_RUN;
                li_setup_dma(&wport->chan,
                             &li_comm2,
                             &devc->lith,
                             wport->hwbuf_paddr,
                             HWBUF_SHIFT,
                             wport->hw_fragshift,
                             wport->sw_channels,
                             wport->sample_size);
                ad1843_setup_dac(&devc->lith,
                                 wport->sw_framerate,
                                 wport->sw_samplefmt,
                                 wport->sw_channels);
                li_enable_interrupts(&devc->lith, WRITE_INTR_MASK);
        }
        DBGRV();
        return 0;
}

/*
 * pcm_shutdown_port - shut down one port (direction) for PCM I/O.
 * Only called from pcm_shutdown.
 */

static void pcm_shutdown_port(vwsnd_dev_t *devc,
                              vwsnd_port_t *aport,
                              unsigned int mask)
{
        unsigned long flags;
        vwsnd_port_hwstate_t hwstate;
        DECLARE_WAITQUEUE(wait, current);

        aport->swstate = SW_INITIAL;
        add_wait_queue(&aport->queue, &wait);
        while (1) {
                set_current_state(TASK_UNINTERRUPTIBLE);
                spin_lock_irqsave(&aport->lock, flags);
                {
                        hwstate = aport->hwstate;
                }               
                spin_unlock_irqrestore(&aport->lock, flags);
                if (hwstate == HW_STOPPED)
                        break;
                schedule();
        }
        current->state = TASK_RUNNING;
        remove_wait_queue(&aport->queue, &wait);
        li_disable_interrupts(&devc->lith, mask);
        if (aport == &devc->rport)
                ad1843_shutdown_adc(&devc->lith);
        else /* aport == &devc->wport) */
                ad1843_shutdown_dac(&devc->lith);
        li_shutdown_dma(&aport->chan);
        vfree(aport->swbuf);
        aport->swbuf = NULL;
        aport->byte_count = 0;
}

/*
 * pcm_shutdown undoes what pcm_setup did.
 * Also sets the ports' swstate to newstate.
 */

static void pcm_shutdown(vwsnd_dev_t *devc,
                         vwsnd_port_t *rport,
                         vwsnd_port_t *wport)
{
        DBGEV("(devc=0x%p, rport=0x%p, wport=0x%p)\n", devc, rport, wport);

        if (rport && rport->swbuf) {
                DBGPV("shutting down rport\n");
                pcm_shutdown_port(devc, rport, READ_INTR_MASK);
        }
        if (wport && wport->swbuf) {
                DBGPV("shutting down wport\n");
                pcm_shutdown_port(devc, wport, WRITE_INTR_MASK);
        }
        DBGRV();
}

static void pcm_copy_in(vwsnd_port_t *rport, int swidx, int hwidx, int nb)
{
        char *src = rport->hwbuf + hwidx;
        char *dst = rport->swbuf + swidx;
        int fmt = rport->sw_samplefmt;

        DBGPV("swidx = %d, hwidx = %d\n", swidx, hwidx);
        ASSERT(rport->hwbuf != NULL);
        ASSERT(rport->swbuf != NULL);
        ASSERT(nb > 0 && (nb % 32) == 0);
        ASSERT(swidx % 32 == 0 && hwidx % 32 == 0);
        ASSERT(swidx >= 0 && swidx + nb <= rport->swbuf_size);
        ASSERT(hwidx >= 0 && hwidx + nb <= rport->hwbuf_size);

        if (fmt == AFMT_MU_LAW || fmt == AFMT_A_LAW || fmt == AFMT_S8) {

                /* See Sample Format Notes above. */

                char *end = src + nb;
                while (src < end)
                        *dst++ = *src++ ^ 0x80;
        } else
                memcpy(dst, src, nb);
}

static void pcm_copy_out(vwsnd_port_t *wport, int swidx, int hwidx, int nb)
{
        char *src = wport->swbuf + swidx;
        char *dst = wport->hwbuf + hwidx;
        int fmt = wport->sw_samplefmt;

        ASSERT(nb > 0 && (nb % 32) == 0);
        ASSERT(wport->hwbuf != NULL);
        ASSERT(wport->swbuf != NULL);
        ASSERT(swidx % 32 == 0 && hwidx % 32 == 0);
        ASSERT(swidx >= 0 && swidx + nb <= wport->swbuf_size);
        ASSERT(hwidx >= 0 && hwidx + nb <= wport->hwbuf_size);
        if (fmt == AFMT_MU_LAW || fmt == AFMT_A_LAW || fmt == AFMT_S8) {

                /* See Sample Format Notes above. */

                char *end = src + nb;
                while (src < end)
                        *dst++ = *src++ ^ 0x80;
        } else
                memcpy(dst, src, nb);
}

/*
 * pcm_output() is called both from baselevel and from interrupt level.
 * This is where audio frames are copied into the hardware-accessible
 * ring buffer.
 *
 * Locking note: The part of this routine that figures out what to do
 * holds wport->lock.  The longer part releases wport->lock, but sets
 * wport->flags & HW_BUSY.  Afterward, it reacquires wport->lock, and
 * checks for more work to do.
 *
 * If another thread calls pcm_output() while HW_BUSY is set, it
 * returns immediately, knowing that the thread that set HW_BUSY will
 * look for more work to do before returning.
 *
 * This has the advantage that port->lock is held for several short
 * periods instead of one long period.  Also, when pcm_output is
 * called from base level, it reenables interrupts.
 */

static void pcm_output(vwsnd_dev_t *devc, int erflown, int nb)
{
        vwsnd_port_t *wport = &devc->wport;
        const int hwmax  = wport->hwbuf_max;
        const int hwsize = wport->hwbuf_size;
        const int swsize = wport->swbuf_size;
        const int fragsize = wport->hw_fragsize;
        unsigned long iflags;

        DBGEV("(devc=0x%p, erflown=%d, nb=%d)\n", devc, erflown, nb);
        spin_lock_irqsave(&wport->lock, iflags);
        if (erflown)
                wport->flags |= ERFLOWN;
        (void) __swb_inc_u(wport, nb);
        if (wport->flags & HW_BUSY) {
                spin_unlock_irqrestore(&wport->lock, iflags);
                DBGPV("returning: HW BUSY\n");
                return;
        }
        if (wport->flags & DISABLED) {
                spin_unlock_irqrestore(&wport->lock, iflags);
                DBGPV("returning: DISABLED\n");
                return;
        }
        wport->flags |= HW_BUSY;
        while (1) {
                int swptr, hwptr, hw_avail, sw_avail, swidx;
                vwsnd_port_hwstate_t hwstate = wport->hwstate;
                vwsnd_port_swstate_t swstate = wport->swstate;
                int hw_unavail;
                ustmsc_t ustmsc;

                hwptr = li_read_hwptr(&wport->chan);
                swptr = li_read_swptr(&wport->chan);
                hw_unavail = (swptr - hwptr + hwsize) % hwsize;
                hw_avail = (hwmax - hw_unavail) & -fragsize;
                sw_avail = wport->swb_i_avail & -fragsize;
                if (sw_avail && swstate == SW_RUN) {
                        if (wport->flags & ERFLOWN) {
                                wport->flags &= ~ERFLOWN;
                        }
                } else if (swstate == SW_INITIAL ||
                         swstate == SW_OFF ||
                         (swstate == SW_DRAIN &&
                          !sw_avail &&
                          (wport->flags & ERFLOWN))) {
                        DBGP("stopping.  hwstate = %d\n", hwstate);
                        if (hwstate != HW_STOPPED) {
                                li_deactivate_dma(&wport->chan);
                                wport->hwstate = HW_STOPPED;
                        }
                        wake_up(&wport->queue);
                        break;
                }
                if (!sw_avail || !hw_avail)
                        break;
                spin_unlock_irqrestore(&wport->lock, iflags);

                /*
                 * We gave up the port lock, but we have the HW_BUSY flag.
                 * Proceed without accessing any nonlocal state.
                 * Do not exit the loop -- must check for more work.
                 */

                swidx = wport->swb_i_idx;
                nb = hw_avail;
                if (nb > sw_avail)
                        nb = sw_avail;
                if (nb > hwsize - swptr)
                        nb = hwsize - swptr; /* don't overflow hwbuf */
                if (nb > swsize - swidx)
                        nb = swsize - swidx; /* don't overflow swbuf */
                ASSERT(nb > 0);
                if (nb % fragsize) {
                        DBGP("nb = %d, fragsize = %d\n", nb, fragsize);
                        DBGP("hw_avail = %d\n", hw_avail);
                        DBGP("sw_avail = %d\n", sw_avail);
                        DBGP("hwsize = %d, swptr = %d\n", hwsize, swptr);
                        DBGP("swsize = %d, swidx = %d\n", swsize, swidx);
                }
                ASSERT(!(nb % fragsize));
                DBGPV("copying swb[%d..%d] to hwb[%d..%d]\n",
                      swidx, swidx + nb, swptr, swptr + nb);
                pcm_copy_out(wport, swidx, swptr, nb);
                li_write_swptr(&wport->chan, (swptr + nb) % hwsize);
                spin_lock_irqsave(&wport->lock, iflags);
                if (hwstate == HW_STOPPED) {
                        DBGPV("starting\n");
                        li_activate_dma(&wport->chan);
                        wport->hwstate = HW_RUNNING;
                        li_read_USTMSC(&wport->chan, &ustmsc);
                        ASSERT(wport->byte_count % wport->frame_size == 0);
                        wport->MSC_offset = ustmsc.msc - wport->byte_count / wport->frame_size;
                }
                __swb_inc_i(wport, nb);
                wport->byte_count += nb;
                wport->frag_count += nb / fragsize;
                ASSERT(nb % fragsize == 0);
                wake_up(&wport->queue);
        }
        wport->flags &= ~HW_BUSY;
        spin_unlock_irqrestore(&wport->lock, iflags);
        DBGRV();
}

/*
 * pcm_input() is called both from baselevel and from interrupt level.
 * This is where audio frames are copied out of the hardware-accessible
 * ring buffer.
 *
 * Locking note: The part of this routine that figures out what to do
 * holds rport->lock.  The longer part releases rport->lock, but sets
 * rport->flags & HW_BUSY.  Afterward, it reacquires rport->lock, and
 * checks for more work to do.
 *
 * If another thread calls pcm_input() while HW_BUSY is set, it
 * returns immediately, knowing that the thread that set HW_BUSY will
 * look for more work to do before returning.
 *
 * This has the advantage that port->lock is held for several short
 * periods instead of one long period.  Also, when pcm_input is
 * called from base level, it reenables interrupts.
 */

static void pcm_input(vwsnd_dev_t *devc, int erflown, int nb)
{
        vwsnd_port_t *rport = &devc->rport;
        const int hwmax  = rport->hwbuf_max;
        const int hwsize = rport->hwbuf_size;
        const int swsize = rport->swbuf_size;
        const int fragsize = rport->hw_fragsize;
        unsigned long iflags;

        DBGEV("(devc=0x%p, erflown=%d, nb=%d)\n", devc, erflown, nb);

        spin_lock_irqsave(&rport->lock, iflags);
        if (erflown)
                rport->flags |= ERFLOWN;
        (void) __swb_inc_u(rport, nb);
        if (rport->flags & HW_BUSY || !rport->swbuf) {
                spin_unlock_irqrestore(&rport->lock, iflags);
                DBGPV("returning: HW BUSY or !swbuf\n");
                return;
        }
        if (rport->flags & DISABLED) {
                spin_unlock_irqrestore(&rport->lock, iflags);
                DBGPV("returning: DISABLED\n");
                return;
        }
        rport->flags |= HW_BUSY;
        while (1) {
                int swptr, hwptr, hw_avail, sw_avail, swidx;
                vwsnd_port_hwstate_t hwstate = rport->hwstate;
                vwsnd_port_swstate_t swstate = rport->swstate;

                hwptr = li_read_hwptr(&rport->chan);
                swptr = li_read_swptr(&rport->chan);
                hw_avail = (hwptr - swptr + hwsize) % hwsize & -fragsize;
                if (hw_avail > hwmax)
                        hw_avail = hwmax;
                sw_avail = rport->swb_i_avail & -fragsize;
                if (swstate != SW_RUN) {
                        DBGP("stopping.  hwstate = %d\n", hwstate);
                        if (hwstate != HW_STOPPED) {
                                li_deactivate_dma(&rport->chan);
                                rport->hwstate = HW_STOPPED;
                        }
                        wake_up(&rport->queue);
                        break;
                }
                if (!sw_avail || !hw_avail)
                        break;
                spin_unlock_irqrestore(&rport->lock, iflags);

                /*
                 * We gave up the port lock, but we have the HW_BUSY flag.
                 * Proceed without accessing any nonlocal state.
                 * Do not exit the loop -- must check for more work.
                 */

                swidx = rport->swb_i_idx;
                nb = hw_avail;
                if (nb > sw_avail)
                        nb = sw_avail;
                if (nb > hwsize - swptr)
                        nb = hwsize - swptr; /* don't overflow hwbuf */
                if (nb > swsize - swidx)
                        nb = swsize - swidx; /* don't overflow swbuf */
                ASSERT(nb > 0);
                if (nb % fragsize) {
                        DBGP("nb = %d, fragsize = %d\n", nb, fragsize);
                        DBGP("hw_avail = %d\n", hw_avail);
                        DBGP("sw_avail = %d\n", sw_avail);
                        DBGP("hwsize = %d, swptr = %d\n", hwsize, swptr);
                        DBGP("swsize = %d, swidx = %d\n", swsize, swidx);
                }
                ASSERT(!(nb % fragsize));
                DBGPV("copying hwb[%d..%d] to swb[%d..%d]\n",
                      swptr, swptr + nb, swidx, swidx + nb);
                pcm_copy_in(rport, swidx, swptr, nb);
                li_write_swptr(&rport->chan, (swptr + nb) % hwsize);
                spin_lock_irqsave(&rport->lock, iflags);
                __swb_inc_i(rport, nb);
                rport->byte_count += nb;
                rport->frag_count += nb / fragsize;
                ASSERT(nb % fragsize == 0);
                wake_up(&rport->queue);
        }
        rport->flags &= ~HW_BUSY;
        spin_unlock_irqrestore(&rport->lock, iflags);
        DBGRV();
}

/*
 * pcm_flush_frag() writes zero samples to fill the current fragment,
 * then flushes it to the hardware.
 *
 * It is only meaningful to flush output, not input.
 */

static void pcm_flush_frag(vwsnd_dev_t *devc)
{
        vwsnd_port_t *wport = &devc->wport;

        DBGPV("swstate = %d\n", wport->swstate);
        if (wport->swstate == SW_RUN) {
                int idx = wport->swb_u_idx;
                int end = (idx + wport->hw_fragsize - 1)
                        >> wport->hw_fragshift
                        << wport->hw_fragshift;
                int nb = end - idx;
                DBGPV("clearing %d bytes\n", nb);
                if (nb)
                        memset(wport->swbuf + idx,
                               (char) wport->zero_word,
                               nb);
                wport->swstate = SW_DRAIN;
                pcm_output(devc, 0, nb);
        }
        DBGRV();
}

/*
 * Wait for output to drain.  This sleeps uninterruptibly because
 * there is nothing intelligent we can do if interrupted.  This
 * means the process will be delayed in responding to the signal.
 */

static void pcm_write_sync(vwsnd_dev_t *devc)
{
        vwsnd_port_t *wport = &devc->wport;
        DECLARE_WAITQUEUE(wait, current);
        unsigned long flags;
        vwsnd_port_hwstate_t hwstate;

        DBGEV("(devc=0x%p)\n", devc);
        add_wait_queue(&wport->queue, &wait);
        while (1) {
                set_current_state(TASK_UNINTERRUPTIBLE);
                spin_lock_irqsave(&wport->lock, flags);
                {
                        hwstate = wport->hwstate;
                }
                spin_unlock_irqrestore(&wport->lock, flags);
                if (hwstate == HW_STOPPED)
                        break;
                schedule();
        }
        current->state = TASK_RUNNING;
        remove_wait_queue(&wport->queue, &wait);
        DBGPV("swstate = %d, hwstate = %d\n", wport->swstate, wport->hwstate);
        DBGRV();
}

/*****************************************************************************/
/* audio driver */

/*
 * seek on an audio device always fails.
 */

static void vwsnd_audio_read_intr(vwsnd_dev_t *devc, unsigned int status)
{
        int overflown = status & LI_INTR_COMM1_OVERFLOW;

        if (status & READ_INTR_MASK)
                pcm_input(devc, overflown, 0);
}

static void vwsnd_audio_write_intr(vwsnd_dev_t *devc, unsigned int status)
{
        int underflown = status & LI_INTR_COMM2_UNDERFLOW;

        if (status & WRITE_INTR_MASK)
                pcm_output(devc, underflown, 0);
}

static irqreturn_t vwsnd_audio_intr(int irq, void *dev_id)
{
        vwsnd_dev_t *devc = dev_id;
        unsigned int status;

        DBGEV("(irq=%d, dev_id=0x%p)\n", irq, dev_id);

        status = li_get_clear_intr_status(&devc->lith);
        vwsnd_audio_read_intr(devc, status);
        vwsnd_audio_write_intr(devc, status);
        return IRQ_HANDLED;
}

static ssize_t vwsnd_audio_do_read(struct file *file,
                                   char *buffer,
                                   size_t count,
                                   loff_t *ppos)
{
        vwsnd_dev_t *devc = file->private_data;
        vwsnd_port_t *rport = ((file->f_mode & FMODE_READ) ?
                               &devc->rport : NULL);
        int ret, nb;

        DBGEV("(file=0x%p, buffer=0x%p, count=%d, ppos=0x%p)\n",
             file, buffer, count, ppos);

        if (!rport)
                return -EINVAL;

        if (rport->swbuf == NULL) {
                vwsnd_port_t *wport = (file->f_mode & FMODE_WRITE) ?
                        &devc->wport : NULL;
                ret = pcm_setup(devc, rport, wport);
                if (ret < 0)
                        return ret;
        }

        if (!access_ok(VERIFY_READ, buffer, count))
                return -EFAULT;
        ret = 0;
        while (count) {
                DECLARE_WAITQUEUE(wait, current);
                add_wait_queue(&rport->queue, &wait);
                while ((nb = swb_inc_u(rport, 0)) == 0) {
                        DBGPV("blocking\n");
                        set_current_state(TASK_INTERRUPTIBLE);
                        if (rport->flags & DISABLED ||
                            file->f_flags & O_NONBLOCK) {
                                current->state = TASK_RUNNING;
                                remove_wait_queue(&rport->queue, &wait);
                                return ret ? ret : -EAGAIN;
                        }
                        schedule();
                        if (signal_pending(current)) {
                                current->state = TASK_RUNNING;
                                remove_wait_queue(&rport->queue, &wait);
                                return ret ? ret : -ERESTARTSYS;
                        }
                }
                current->state = TASK_RUNNING;
                remove_wait_queue(&rport->queue, &wait);
                pcm_input(devc, 0, 0);
                /* nb bytes are available in userbuf. */
                if (nb > count)
                        nb = count;
                DBGPV("nb = %d\n", nb);
                if (copy_to_user(buffer, rport->swbuf + rport->swb_u_idx, nb))
                        return -EFAULT;
                (void) swb_inc_u(rport, nb);
                buffer += nb;
                count -= nb;
                ret += nb;
        }
        DBGPV("returning %d\n", ret);
        return ret;
}

static ssize_t vwsnd_audio_read(struct file *file,
                                char *buffer,
                                size_t count,
                                loff_t *ppos)
{
        vwsnd_dev_t *devc = file->private_data;
        ssize_t ret;

        mutex_lock(&devc->io_mutex);
        ret = vwsnd_audio_do_read(file, buffer, count, ppos);
        mutex_unlock(&devc->io_mutex);
        return ret;
}

static ssize_t vwsnd_audio_do_write(struct file *file,
                                    const char *buffer,
                                    size_t count,
                                    loff_t *ppos)
{
        vwsnd_dev_t *devc = file->private_data;
        vwsnd_port_t *wport = ((file->f_mode & FMODE_WRITE) ?
                               &devc->wport : NULL);
        int ret, nb;

        DBGEV("(file=0x%p, buffer=0x%p, count=%d, ppos=0x%p)\n",
              file, buffer, count, ppos);

        if (!wport)
                return -EINVAL;

        if (wport->swbuf == NULL) {
                vwsnd_port_t *rport = (file->f_mode & FMODE_READ) ?
                        &devc->rport : NULL;
                ret = pcm_setup(devc, rport, wport);
                if (ret < 0)
                        return ret;
        }
        if (!access_ok(VERIFY_WRITE, buffer, count))
                return -EFAULT;
        ret = 0;
        while (count) {
                DECLARE_WAITQUEUE(wait, current);
                add_wait_queue(&wport->queue, &wait);
                while ((nb = swb_inc_u(wport, 0)) == 0) {
                        set_current_state(TASK_INTERRUPTIBLE);
                        if (wport->flags & DISABLED ||
                            file->f_flags & O_NONBLOCK) {
                                current->state = TASK_RUNNING;
                                remove_wait_queue(&wport->queue, &wait);
                                return ret ? ret : -EAGAIN;
                        }
                        schedule();
                        if (signal_pending(current)) {
                                current->state = TASK_RUNNING;
                                remove_wait_queue(&wport->queue, &wait);
                                return ret ? ret : -ERESTARTSYS;
                        }
                }
                current->state = TASK_RUNNING;
                remove_wait_queue(&wport->queue, &wait);
                /* nb bytes are available in userbuf. */
                if (nb > count)
                        nb = count;
                DBGPV("nb = %d\n", nb);
                if (copy_from_user(wport->swbuf + wport->swb_u_idx, buffer, nb))
                        return -EFAULT;
                pcm_output(devc, 0, nb);
                buffer += nb;
                count -= nb;
                ret += nb;
        }
        DBGPV("returning %d\n", ret);
        return ret;
}

static ssize_t vwsnd_audio_write(struct file *file,
                                 const char *buffer,
                                 size_t count,
                                 loff_t *ppos)
{
        vwsnd_dev_t *devc = file->private_data;
        ssize_t ret;

        mutex_lock(&devc->io_mutex);
        ret = vwsnd_audio_do_write(file, buffer, count, ppos);
        mutex_unlock(&devc->io_mutex);
        return ret;
}

/* No kernel lock - fine */
static unsigned int vwsnd_audio_poll(struct file *file,
                                     struct poll_table_struct *wait)
{
        vwsnd_dev_t *devc = (vwsnd_dev_t *) file->private_data;
        vwsnd_port_t *rport = (file->f_mode & FMODE_READ) ?
                &devc->rport : NULL;
        vwsnd_port_t *wport = (file->f_mode & FMODE_WRITE) ?
                &devc->wport : NULL;
        unsigned int mask = 0;

        DBGEV("(file=0x%p, wait=0x%p)\n", file, wait);

        ASSERT(rport || wport);
        if (rport) {
                poll_wait(file, &rport->queue, wait);
                if (swb_inc_u(rport, 0))
                        mask |= (POLLIN | POLLRDNORM);
        }
        if (wport) {
                poll_wait(file, &wport->queue, wait);
                if (wport->swbuf == NULL || swb_inc_u(wport, 0))
                        mask |= (POLLOUT | POLLWRNORM);
        }

        DBGPV("returning 0x%x\n", mask);
        return mask;
}

static int vwsnd_audio_do_ioctl(struct inode *inode,
                                struct file *file,
                                unsigned int cmd,
                                unsigned long arg)
{
        vwsnd_dev_t *devc = (vwsnd_dev_t *) file->private_data;
        vwsnd_port_t *rport = (file->f_mode & FMODE_READ) ?
                &devc->rport : NULL;
        vwsnd_port_t *wport = (file->f_mode & FMODE_WRITE) ?
                &devc->wport : NULL;
        vwsnd_port_t *aport = rport ? rport : wport;
        struct audio_buf_info buf_info;
        struct count_info info;
        unsigned long flags;
        int ival;

        
        DBGEV("(inode=0x%p, file=0x%p, cmd=0x%x, arg=0x%lx)\n",
              inode, file, cmd, arg);
        switch (cmd) {
        case OSS_GETVERSION:            /* _SIOR ('M', 118, int) */
                DBGX("OSS_GETVERSION\n");
                ival = SOUND_VERSION;
                return put_user(ival, (int *) arg);

        case SNDCTL_DSP_GETCAPS:        /* _SIOR ('P',15, int) */
                DBGX("SNDCTL_DSP_GETCAPS\n");
                ival = DSP_CAP_DUPLEX | DSP_CAP_REALTIME | DSP_CAP_TRIGGER;
                return put_user(ival, (int *) arg);

        case SNDCTL_DSP_GETFMTS:        /* _SIOR ('P',11, int) */
                DBGX("SNDCTL_DSP_GETFMTS\n");
                ival = (AFMT_S16_LE | AFMT_MU_LAW | AFMT_A_LAW |
                        AFMT_U8 | AFMT_S8);
                return put_user(ival, (int *) arg);
                break;

        case SOUND_PCM_READ_RATE:       /* _SIOR ('P', 2, int) */
                DBGX("SOUND_PCM_READ_RATE\n");
                ival = aport->sw_framerate;
                return put_user(ival, (int *) arg);

        case SOUND_PCM_READ_CHANNELS:   /* _SIOR ('P', 6, int) */
                DBGX("SOUND_PCM_READ_CHANNELS\n");
                ival = aport->sw_channels;
                return put_user(ival, (int *) arg);

        case SNDCTL_DSP_SPEED:          /* _SIOWR('P', 2, int) */
                if (get_user(ival, (int *) arg))
                        return -EFAULT;
                DBGX("SNDCTL_DSP_SPEED %d\n", ival);
                if (ival) {
                        if (aport->swstate != SW_INITIAL) {
                                DBGX("SNDCTL_DSP_SPEED failed: swstate = %d\n",
                                     aport->swstate);
                                return -EINVAL;
                        }
                        if (ival < MIN_SPEED)
                                ival = MIN_SPEED;
                        if (ival > MAX_SPEED)
                                ival = MAX_SPEED;
                        if (rport)
                                rport->sw_framerate = ival;
                        if (wport)
                                wport->sw_framerate = ival;
                } else
                        ival = aport->sw_framerate;
                return put_user(ival, (int *) arg);

        case SNDCTL_DSP_STEREO:         /* _SIOWR('P', 3, int) */
                if (get_user(ival, (int *) arg))
                        return -EFAULT;
                DBGX("SNDCTL_DSP_STEREO %d\n", ival);
                if (ival != 0 && ival != 1)
                        return -EINVAL;
                if (aport->swstate != SW_INITIAL)
                        return -EINVAL;
                if (rport)
                        rport->sw_channels = ival + 1;
                if (wport)
                        wport->sw_channels = ival + 1;
                return put_user(ival, (int *) arg);

        case SNDCTL_DSP_CHANNELS:       /* _SIOWR('P', 6, int) */
                if (get_user(ival, (int *) arg))
                        return -EFAULT;
                DBGX("SNDCTL_DSP_CHANNELS %d\n", ival);
                if (ival != 1 && ival != 2)
                        return -EINVAL;
                if (aport->swstate != SW_INITIAL)
                        return -EINVAL;
                if (rport)
                        rport->sw_channels = ival;
                if (wport)
                        wport->sw_channels = ival;
                return put_user(ival, (int *) arg);

        case SNDCTL_DSP_GETBLKSIZE:     /* _SIOWR('P', 4, int) */
                ival = pcm_setup(devc, rport, wport);
                if (ival < 0) {
                        DBGX("SNDCTL_DSP_GETBLKSIZE failed, errno %d\n", ival);
                        return ival;
                }
                ival = 1 << aport->sw_fragshift;
                DBGX("SNDCTL_DSP_GETBLKSIZE returning %d\n", ival);
                return put_user(ival, (int *) arg);

        case SNDCTL_DSP_SETFRAGMENT:    /* _SIOWR('P',10, int) */
                if (get_user(ival, (int *) arg))
                        return -EFAULT;
                DBGX("SNDCTL_DSP_SETFRAGMENT %d:%d\n",
                     ival >> 16, ival & 0xFFFF);
                if (aport->swstate != SW_INITIAL)
                        return -EINVAL;
                {
                        int sw_fragshift = ival & 0xFFFF;
                        int sw_subdivshift = aport->sw_subdivshift;
                        int hw_fragshift = sw_fragshift - sw_subdivshift;
                        int sw_fragcount = (ival >> 16) & 0xFFFF;
                        int hw_fragsize;
                        if (hw_fragshift < MIN_FRAGSHIFT)
                                hw_fragshift = MIN_FRAGSHIFT;
                        if (hw_fragshift > MAX_FRAGSHIFT)
                                hw_fragshift = MAX_FRAGSHIFT;
                        sw_fragshift = hw_fragshift + aport->sw_subdivshift;
                        hw_fragsize = 1 << hw_fragshift;
                        if (sw_fragcount < MIN_FRAGCOUNT(hw_fragsize))
                                sw_fragcount = MIN_FRAGCOUNT(hw_fragsize);
                        if (sw_fragcount > MAX_FRAGCOUNT(hw_fragsize))
                                sw_fragcount = MAX_FRAGCOUNT(hw_fragsize);
                        DBGPV("sw_fragshift = %d\n", sw_fragshift);
                        DBGPV("rport = 0x%p, wport = 0x%p\n", rport, wport);
                        if (rport) {
                                rport->sw_fragshift = sw_fragshift;
                                rport->sw_fragcount = sw_fragcount;
                        }
                        if (wport) {
                                wport->sw_fragshift = sw_fragshift;
                                wport->sw_fragcount = sw_fragcount;
                        }
                        ival = sw_fragcount << 16 | sw_fragshift;
                }
                DBGX("SNDCTL_DSP_SETFRAGMENT returns %d:%d\n",
                      ival >> 16, ival & 0xFFFF);
                return put_user(ival, (int *) arg);

        case SNDCTL_DSP_SUBDIVIDE:      /* _SIOWR('P', 9, int) */
                if (get_user(ival, (int *) arg))
                        return -EFAULT;
                DBGX("SNDCTL_DSP_SUBDIVIDE %d\n", ival);
                if (aport->swstate != SW_INITIAL)
                        return -EINVAL;
                {
                        int subdivshift;
                        int hw_fragshift, hw_fragsize, hw_fragcount;
                        switch (ival) {
                        case 1: subdivshift = 0; break;
                        case 2: subdivshift = 1; break;
                        case 4: subdivshift = 2; break;
                        default: return -EINVAL;
                        }
                        hw_fragshift = aport->sw_fragshift - subdivshift;
                        if (hw_fragshift < MIN_FRAGSHIFT ||
                            hw_fragshift > MAX_FRAGSHIFT)
                                return -EINVAL;
                        hw_fragsize = 1 << hw_fragshift;
                        hw_fragcount = aport->sw_fragcount >> subdivshift;
                        if (hw_fragcount < MIN_FRAGCOUNT(hw_fragsize) ||
                            hw_fragcount > MAX_FRAGCOUNT(hw_fragsize))
                                return -EINVAL;
                        if (rport)
                                rport->sw_subdivshift = subdivshift;
                        if (wport)
                                wport->sw_subdivshift = subdivshift;
                }
                return 0;

        case SNDCTL_DSP_SETFMT:         /* _SIOWR('P',5, int) */
                if (get_user(ival, (int *) arg))
                        return -EFAULT;
                DBGX("SNDCTL_DSP_SETFMT %d\n", ival);
                if (ival != AFMT_QUERY) {
                        if (aport->swstate != SW_INITIAL) {
                                DBGP("SETFMT failed, swstate = %d\n",
                                     aport->swstate);
                                return -EINVAL;
                        }
                        switch (ival) {
                        case AFMT_MU_LAW:
                        case AFMT_A_LAW:
                        case AFMT_U8:
                        case AFMT_S8:
                        case AFMT_S16_LE:
                                if (rport)
                                        rport->sw_samplefmt = ival;
                                if (wport)
                                        wport->sw_samplefmt = ival;
                                break;
                        default:
                                return -EINVAL;
                        }
                }
                ival = aport->sw_samplefmt;
                return put_user(ival, (int *) arg);

        case SNDCTL_DSP_GETOSPACE:      /* _SIOR ('P',12, audio_buf_info) */
                DBGXV("SNDCTL_DSP_GETOSPACE\n");
                if (!wport)
                        return -EINVAL;
                ival = pcm_setup(devc, rport, wport);
                if (ival < 0)
                        return ival;
                ival = swb_inc_u(wport, 0);
                buf_info.fragments = ival >> wport->sw_fragshift;
                buf_info.fragstotal = wport->sw_fragcount;
                buf_info.fragsize = 1 << wport->sw_fragshift;
                buf_info.bytes = ival;
                DBGXV("SNDCTL_DSP_GETOSPACE returns { %d %d %d %d }\n",
                     buf_info.fragments, buf_info.fragstotal,
                     buf_info.fragsize, buf_info.bytes);
                if (copy_to_user((void *) arg, &buf_info, sizeof buf_info))
                        return -EFAULT;
                return 0;

        case SNDCTL_DSP_GETISPACE:      /* _SIOR ('P',13, audio_buf_info) */
                DBGX("SNDCTL_DSP_GETISPACE\n");
                if (!rport)
                        return -EINVAL;
                ival = pcm_setup(devc, rport, wport);
                if (ival < 0)
                        return ival;
                ival = swb_inc_u(rport, 0);
                buf_info.fragments = ival >> rport->sw_fragshift;
                buf_info.fragstotal = rport->sw_fragcount;
                buf_info.fragsize = 1 << rport->sw_fragshift;
                buf_info.bytes = ival;
                DBGX("SNDCTL_DSP_GETISPACE returns { %d %d %d %d }\n",
                     buf_info.fragments, buf_info.fragstotal,
                     buf_info.fragsize, buf_info.bytes);
                if (copy_to_user((void *) arg, &buf_info, sizeof buf_info))
                        return -EFAULT;
                return 0;

        case SNDCTL_DSP_NONBLOCK:       /* _SIO  ('P',14) */
                DBGX("SNDCTL_DSP_NONBLOCK\n");
                file->f_flags |= O_NONBLOCK;
                return 0;

        case SNDCTL_DSP_RESET:          /* _SIO  ('P', 0) */
                DBGX("SNDCTL_DSP_RESET\n");
                /*
                 * Nothing special needs to be done for input.  Input
                 * samples sit in swbuf, but it will be reinitialized
                 * to empty when pcm_setup() is called.
                 */
                if (wport && wport->swbuf) {
                        wport->swstate = SW_INITIAL;
                        pcm_output(devc, 0, 0);
                        pcm_write_sync(devc);
                }
                pcm_shutdown(devc, rport, wport);
                return 0;

        case SNDCTL_DSP_SYNC:           /* _SIO  ('P', 1) */
                DBGX("SNDCTL_DSP_SYNC\n");
                if (wport) {
                        pcm_flush_frag(devc);
                        pcm_write_sync(devc);
                }
                pcm_shutdown(devc, rport, wport);
                return 0;

        case SNDCTL_DSP_POST:           /* _SIO  ('P', 8) */
                DBGX("SNDCTL_DSP_POST\n");
                if (!wport)
                        return -EINVAL;
                pcm_flush_frag(devc);
                return 0;

        case SNDCTL_DSP_GETIPTR:        /* _SIOR ('P', 17, count_info) */
                DBGX("SNDCTL_DSP_GETIPTR\n");
                if (!rport)
                        return -EINVAL;
                spin_lock_irqsave(&rport->lock, flags);
                {
                        ustmsc_t ustmsc;
                        if (rport->hwstate == HW_RUNNING) {
                                ASSERT(rport->swstate == SW_RUN);
                                li_read_USTMSC(&rport->chan, &ustmsc);
                                info.bytes = ustmsc.msc - rport->MSC_offset;
                                info.bytes *= rport->frame_size;
                        } else {
                                info.bytes = rport->byte_count;
                        }
                        info.blocks = rport->frag_count;
                        info.ptr = 0;   /* not implemented */
                        rport->frag_count = 0;
                }
                spin_unlock_irqrestore(&rport->lock, flags);
                if (copy_to_user((void *) arg, &info, sizeof info))
                        return -EFAULT;
                return 0;

        case SNDCTL_DSP_GETOPTR:        /* _SIOR ('P',18, count_info) */
                DBGX("SNDCTL_DSP_GETOPTR\n");
                if (!wport)
                        return -EINVAL;
                spin_lock_irqsave(&wport->lock, flags);
                {
                        ustmsc_t ustmsc;
                        if (wport->hwstate == HW_RUNNING) {
                                ASSERT(wport->swstate == SW_RUN);
                                li_read_USTMSC(&wport->chan, &ustmsc);
                                info.bytes = ustmsc.msc - wport->MSC_offset;
                                info.bytes *= wport->frame_size;
                        } else {
                                info.bytes = wport->byte_count;
                        }
                        info.blocks = wport->frag_count;
                        info.ptr = 0;   /* not implemented */
                        wport->frag_count = 0;
                }
                spin_unlock_irqrestore(&wport->lock, flags);
                if (copy_to_user((void *) arg, &info, sizeof info))
                        return -EFAULT;
                return 0;

        case SNDCTL_DSP_GETODELAY:      /* _SIOR ('P', 23, int) */
                DBGX("SNDCTL_DSP_GETODELAY\n");
                if (!wport)
                        return -EINVAL;
                spin_lock_irqsave(&wport->lock, flags);
                {
                        int fsize = wport->frame_size;
                        ival = wport->swb_i_avail / fsize;
                        if (wport->hwstate == HW_RUNNING) {
                                int swptr, hwptr, hwframes, hwbytes, hwsize;
                                int totalhwbytes;
                                ustmsc_t ustmsc;

                                hwsize = wport->hwbuf_size;
                                swptr = li_read_swptr(&wport->chan);
                                li_read_USTMSC(&wport->chan, &ustmsc);
                                hwframes = ustmsc.msc - wport->MSC_offset;
                                totalhwbytes = hwframes * fsize;
                                hwptr = totalhwbytes % hwsize;
                                hwbytes = (swptr - hwptr + hwsize) % hwsize;
                                ival += hwbytes / fsize;
                        }
                }
                spin_unlock_irqrestore(&wport->lock, flags);
                return put_user(ival, (int *) arg);

        case SNDCTL_DSP_PROFILE:        /* _SIOW ('P', 23, int) */
                DBGX("SNDCTL_DSP_PROFILE\n");

                /*
                 * Thomas Sailer explains SNDCTL_DSP_PROFILE
                 * (private email, March 24, 1999):
                 *
                 *     This gives the sound driver a hint on what it
                 *     should do with partial fragments
                 *     (i.e. fragments partially filled with write).
                 *     This can direct the driver to zero them or
                 *     leave them alone.  But don't ask me what this
                 *     is good for, my driver just zeroes the last
                 *     fragment before the receiver stops, no idea
                 *     what good for any other behaviour could
                 *     be. Implementing it as NOP seems safe.
                 */

                break;

        case SNDCTL_DSP_GETTRIGGER:     /* _SIOR ('P',16, int) */
                DBGX("SNDCTL_DSP_GETTRIGGER\n");
                ival = 0;
                if (rport) {
                        spin_lock_irqsave(&rport->lock, flags);
                        {
                                if (!(rport->flags & DISABLED))
                                        ival |= PCM_ENABLE_INPUT;
                        }
                        spin_unlock_irqrestore(&rport->lock, flags);
                }
                if (wport) {
                        spin_lock_irqsave(&wport->lock, flags);
                        {
                                if (!(wport->flags & DISABLED))
                                        ival |= PCM_ENABLE_OUTPUT;
                        }
                        spin_unlock_irqrestore(&wport->lock, flags);
                }
                return put_user(ival, (int *) arg);

        case SNDCTL_DSP_SETTRIGGER:     /* _SIOW ('P',16, int) */
                if (get_user(ival, (int *) arg))
                        return -EFAULT;
                DBGX("SNDCTL_DSP_SETTRIGGER %d\n", ival);

                /*
                 * If user is disabling I/O and port is not in initial
                 * state, fail with EINVAL.
                 */

                if (((rport && !(ival & PCM_ENABLE_INPUT)) ||
                     (wport && !(ival & PCM_ENABLE_OUTPUT))) &&
                    aport->swstate != SW_INITIAL)
                        return -EINVAL;

                if (rport) {
                        vwsnd_port_hwstate_t hwstate;
                        spin_lock_irqsave(&rport->lock, flags);
                        {
                                hwstate = rport->hwstate;
                                if (ival & PCM_ENABLE_INPUT)
                                        rport->flags &= ~DISABLED;
                                else
                                        rport->flags |= DISABLED;
                        }
                        spin_unlock_irqrestore(&rport->lock, flags);
                        if (hwstate != HW_RUNNING && ival & PCM_ENABLE_INPUT) {

                                if (rport->swstate == SW_INITIAL)
                                        pcm_setup(devc, rport, wport);
                                else
                                        li_activate_dma(&rport->chan);
                        }
                }
                if (wport) {
                        vwsnd_port_flags_t pflags;
                        spin_lock_irqsave(&wport->lock, flags);
                        {
                                pflags = wport->flags;
                                if (ival & PCM_ENABLE_OUTPUT)
                                        wport->flags &= ~DISABLED;
                                else
                                        wport->flags |= DISABLED;
                        }
                        spin_unlock_irqrestore(&wport->lock, flags);
                        if (pflags & DISABLED && ival & PCM_ENABLE_OUTPUT) {
                                if (wport->swstate == SW_RUN)
                                        pcm_output(devc, 0, 0);
                        }
                }
                return 0;

        default:
                DBGP("unknown ioctl 0x%x\n", cmd);
                return -EINVAL;
        }
        DBGP("unimplemented ioctl 0x%x\n", cmd);
        return -EINVAL;
}

static int vwsnd_audio_ioctl(struct inode *inode,
                                struct file *file,
                                unsigned int cmd,
                                unsigned long arg)
{
        vwsnd_dev_t *devc = (vwsnd_dev_t *) file->private_data;
        int ret;

        mutex_lock(&devc->io_mutex);
        ret = vwsnd_audio_do_ioctl(inode, file, cmd, arg);
        mutex_unlock(&devc->io_mutex);
        return ret;
}

/* No mmap. */

static int vwsnd_audio_mmap(struct file *file, struct vm_area_struct *vma)
{
        DBGE("(file=0x%p, vma=0x%p)\n", file, vma);
        return -ENODEV;
}

/*
 * Open the audio device for read and/or write.
 *
 * Returns 0 on success, -errno on failure.
 */

static int vwsnd_audio_open(struct inode *inode, struct file *file)
{
        vwsnd_dev_t *devc;
        int minor = iminor(inode);
        int sw_samplefmt;

        DBGE("(inode=0x%p, file=0x%p)\n", inode, file);

        INC_USE_COUNT;
        for (devc = vwsnd_dev_list; devc; devc = devc->next_dev)
                if ((devc->audio_minor & ~0x0F) == (minor & ~0x0F))
                        break;

        if (devc == NULL) {
                DEC_USE_COUNT;
                return -ENODEV;
        }

        mutex_lock(&devc->open_mutex);
        while (devc->open_mode & file->f_mode) {
                mutex_unlock(&devc->open_mutex);
                if (file->f_flags & O_NONBLOCK) {
                        DEC_USE_COUNT;
                        return -EBUSY;
                }
                interruptible_sleep_on(&devc->open_wait);
                if (signal_pending(current)) {
                        DEC_USE_COUNT;
                        return -ERESTARTSYS;
                }
                mutex_lock(&devc->open_mutex);
        }
        devc->open_mode |= file->f_mode & (FMODE_READ | FMODE_WRITE);
        mutex_unlock(&devc->open_mutex);

        /* get default sample format from minor number. */

        sw_samplefmt = 0;
        if ((minor & 0xF) == SND_DEV_DSP)
                sw_samplefmt = AFMT_U8;
        else if ((minor & 0xF) == SND_DEV_AUDIO)
                sw_samplefmt = AFMT_MU_LAW;
        else if ((minor & 0xF) == SND_DEV_DSP16)
                sw_samplefmt = AFMT_S16_LE;
        else
                ASSERT(0);

        /* Initialize vwsnd_ports. */

        mutex_lock(&devc->io_mutex);
        {
                if (file->f_mode & FMODE_READ) {
                        devc->rport.swstate        = SW_INITIAL;
                        devc->rport.flags          = 0;
                        devc->rport.sw_channels    = 1;
                        devc->rport.sw_samplefmt   = sw_samplefmt;
                        devc->rport.sw_framerate   = 8000;
                        devc->rport.sw_fragshift   = DEFAULT_FRAGSHIFT;
                        devc->rport.sw_fragcount   = DEFAULT_FRAGCOUNT;
                        devc->rport.sw_subdivshift = DEFAULT_SUBDIVSHIFT;
                        devc->rport.byte_count     = 0;
                        devc->rport.frag_count     = 0;
                }
                if (file->f_mode & FMODE_WRITE) {
                        devc->wport.swstate        = SW_INITIAL;
                        devc->wport.flags          = 0;
                        devc->wport.sw_channels    = 1;
                        devc->wport.sw_samplefmt   = sw_samplefmt;
                        devc->wport.sw_framerate   = 8000;
                        devc->wport.sw_fragshift   = DEFAULT_FRAGSHIFT;
                        devc->wport.sw_fragcount   = DEFAULT_FRAGCOUNT;
                        devc->wport.sw_subdivshift = DEFAULT_SUBDIVSHIFT;
                        devc->wport.byte_count     = 0;
                        devc->wport.frag_count     = 0;
                }
        }
        mutex_unlock(&devc->io_mutex);

        file->private_data = devc;
        DBGRV();
        return 0;
}

/*
 * Release (close) the audio device.
 */

static int vwsnd_audio_release(struct inode *inode, struct file *file)
{
        vwsnd_dev_t *devc = (vwsnd_dev_t *) file->private_data;
        vwsnd_port_t *wport = NULL, *rport = NULL;
        int err = 0;

        lock_kernel();
        mutex_lock(&devc->io_mutex);
        {
                DBGEV("(inode=0x%p, file=0x%p)\n", inode, file);

                if (file->f_mode & FMODE_READ)
                        rport = &devc->rport;
                if (file->f_mode & FMODE_WRITE) {
                        wport = &devc->wport;
                        pcm_flush_frag(devc);
                        pcm_write_sync(devc);
                }
                pcm_shutdown(devc, rport, wport);
                if (rport)
                        rport->swstate = SW_OFF;
                if (wport)
                        wport->swstate = SW_OFF;
        }
        mutex_unlock(&devc->io_mutex);

        mutex_lock(&devc->open_mutex);
        {
                devc->open_mode &= ~file->f_mode;
        }
        mutex_unlock(&devc->open_mutex);
        wake_up(&devc->open_wait);
        DEC_USE_COUNT;
        DBGR();
        unlock_kernel();
        return err;
}

static const struct file_operations vwsnd_audio_fops = {
        .owner =        THIS_MODULE,
        .llseek =       no_llseek,
        .read =         vwsnd_audio_read,
        .write =        vwsnd_audio_write,
        .poll =         vwsnd_audio_poll,
        .ioctl =        vwsnd_audio_ioctl,
        .mmap =         vwsnd_audio_mmap,
        .open =         vwsnd_audio_open,
        .release =      vwsnd_audio_release,
};

/*****************************************************************************/
/* mixer driver */

/* open the mixer device. */

static int vwsnd_mixer_open(struct inode *inode, struct file *file)
{
        vwsnd_dev_t *devc;

        DBGEV("(inode=0x%p, file=0x%p)\n", inode, file);

        INC_USE_COUNT;
        for (devc = vwsnd_dev_list; devc; devc = devc->next_dev)
                if (devc->mixer_minor == iminor(inode))
                        break;

        if (devc == NULL) {
                DEC_USE_COUNT;
                return -ENODEV;
        }
        file->private_data = devc;
        return 0;
}

/* release (close) the mixer device. */

static int vwsnd_mixer_release(struct inode *inode, struct file *file)
{
        DBGEV("(inode=0x%p, file=0x%p)\n", inode, file);
        DEC_USE_COUNT;
        return 0;
}

/* mixer_read_ioctl handles all read ioctls on the mixer device. */

static int mixer_read_ioctl(vwsnd_dev_t *devc, unsigned int nr, void __user *arg)
{
        int val = -1;

        DBGEV("(devc=0x%p, nr=0x%x, arg=0x%p)\n", devc, nr, arg);

        switch (nr) {
        case SOUND_MIXER_CAPS:
                val = SOUND_CAP_EXCL_INPUT;
                break;

        case SOUND_MIXER_DEVMASK:
                val = (SOUND_MASK_PCM | SOUND_MASK_LINE |
                       SOUND_MASK_MIC | SOUND_MASK_CD | SOUND_MASK_RECLEV);
                break;

        case SOUND_MIXER_STEREODEVS:
                val = (SOUND_MASK_PCM | SOUND_MASK_LINE |
                       SOUND_MASK_MIC | SOUND_MASK_CD | SOUND_MASK_RECLEV);
                break;

        case SOUND_MIXER_OUTMASK:
                val = (SOUND_MASK_PCM | SOUND_MASK_LINE |
                       SOUND_MASK_MIC | SOUND_MASK_CD);
                break;

        case SOUND_MIXER_RECMASK:
                val = (SOUND_MASK_PCM | SOUND_MASK_LINE |
                       SOUND_MASK_MIC | SOUND_MASK_CD);
                break;

        case SOUND_MIXER_PCM:
                val = ad1843_get_gain(&devc->lith, &ad1843_gain_PCM);
                break;

        case SOUND_MIXER_LINE:
                val = ad1843_get_gain(&devc->lith, &ad1843_gain_LINE);
                break;

        case SOUND_MIXER_MIC:
                val = ad1843_get_gain(&devc->lith, &ad1843_gain_MIC);
                break;

        case SOUND_MIXER_CD:
                val = ad1843_get_gain(&devc->lith, &ad1843_gain_CD);
                break;

        case SOUND_MIXER_RECLEV:
                val = ad1843_get_gain(&devc->lith, &ad1843_gain_RECLEV);
                break;

        case SOUND_MIXER_RECSRC:
                val = ad1843_get_recsrc(&devc->lith);
                break;

        case SOUND_MIXER_OUTSRC:
                val = ad1843_get_outsrc(&devc->lith);
                break;

        default:
                return -EINVAL;
        }
        return put_user(val, (int __user *) arg);
}

/* mixer_write_ioctl handles all write ioctls on the mixer device. */

static int mixer_write_ioctl(vwsnd_dev_t *devc, unsigned int nr, void __user *arg)
{
        int val;
        int err;

        DBGEV("(devc=0x%p, nr=0x%x, arg=0x%p)\n", devc, nr, arg);

        err = get_user(val, (int __user *) arg);
        if (err)
                return -EFAULT;
        switch (nr) {
        case SOUND_MIXER_PCM:
                val = ad1843_set_gain(&devc->lith, &ad1843_gain_PCM, val);
                break;

        case SOUND_MIXER_LINE:
                val = ad1843_set_gain(&devc->lith, &ad1843_gain_LINE, val);
                break;

        case SOUND_MIXER_MIC:
                val = ad1843_set_gain(&devc->lith, &ad1843_gain_MIC, val);
                break;

        case SOUND_MIXER_CD:
                val = ad1843_set_gain(&devc->lith, &ad1843_gain_CD, val);
                break;

        case SOUND_MIXER_RECLEV:
                val = ad1843_set_gain(&devc->lith, &ad1843_gain_RECLEV, val);
                break;

        case SOUND_MIXER_RECSRC:
                if (devc->rport.swbuf || devc->wport.swbuf)
                        return -EBUSY;  /* can't change recsrc while running */
                val = ad1843_set_recsrc(&devc->lith, val);
                break;

        case SOUND_MIXER_OUTSRC:
                val = ad1843_set_outsrc(&devc->lith, val);
                break;

        default:
                return -EINVAL;
        }
        if (val < 0)
                return val;
        return put_user(val, (int __user *) arg);
}

/* This is the ioctl entry to the mixer driver. */

static int vwsnd_mixer_ioctl(struct inode *ioctl,
                              struct file *file,
                              unsigned int cmd,
                              unsigned long arg)
{
        vwsnd_dev_t *devc = (vwsnd_dev_t *) file->private_data;
        const unsigned int nrmask = _IOC_NRMASK << _IOC_NRSHIFT;
        const unsigned int nr = (cmd & nrmask) >> _IOC_NRSHIFT;
        int retval;

        DBGEV("(devc=0x%p, cmd=0x%x, arg=0x%lx)\n", devc, cmd, arg);

        mutex_lock(&devc->mix_mutex);
        {
                if ((cmd & ~nrmask) == MIXER_READ(0))
                        retval = mixer_read_ioctl(devc, nr, (void __user *) arg);
                else if ((cmd & ~nrmask) == MIXER_WRITE(0))
                        retval = mixer_write_ioctl(devc, nr, (void __user *) arg);
                else
                        retval = -EINVAL;
        }
        mutex_unlock(&devc->mix_mutex);
        return retval;
}

static const struct file_operations vwsnd_mixer_fops = {
        .owner =        THIS_MODULE,
        .llseek =       no_llseek,
        .ioctl =        vwsnd_mixer_ioctl,
        .open =         vwsnd_mixer_open,
        .release =      vwsnd_mixer_release,
};

/*****************************************************************************/
/* probe/attach/unload */

/* driver probe routine.  Return nonzero if hardware is found. */

static int __init probe_vwsnd(struct address_info *hw_config)
{
        lithium_t lith;
        int w;
        unsigned long later;

        DBGEV("(hw_config=0x%p)\n", hw_config);

        /* XXX verify lithium present (to prevent crash on non-vw) */

        if (li_create(&lith, hw_config->io_base) != 0) {
                printk(KERN_WARNING "probe_vwsnd: can't map lithium\n");
                return 0;
        }
        later = jiffies + 2;
        li_writel(&lith, LI_HOST_CONTROLLER, LI_HC_LINK_ENABLE);
        do {
                w = li_readl(&lith, LI_HOST_CONTROLLER);
        } while (w == LI_HC_LINK_ENABLE && time_before(jiffies, later));
        
        li_destroy(&lith);

        DBGPV("HC = 0x%04x\n", w);

        if ((w == LI_HC_LINK_ENABLE) || (w & LI_HC_LINK_CODEC)) {

                /* This may indicate a beta machine with no audio,
                 * or a future machine with different audio.
                 * On beta-release 320 w/ no audio, HC == 0x4000 */

                printk(KERN_WARNING "probe_vwsnd: audio codec not found\n");
                return 0;
        }

        if (w & LI_HC_LINK_FAILURE) {
                printk(KERN_WARNING "probe_vwsnd: can't init audio codec\n");
                return 0;
        }

        printk(KERN_INFO "vwsnd: lithium audio at mmio %#x irq %d\n",
                hw_config->io_base, hw_config->irq);

        return 1;
}

/*
 * driver attach routine.  Initialize driver data structures and
 * initialize hardware.  A new vwsnd_dev_t is allocated and put
 * onto the global list, vwsnd_dev_list.
 *
 * Return +minor_dev on success, -errno on failure.
 */

static int __init attach_vwsnd(struct address_info *hw_config)
{
        vwsnd_dev_t *devc = NULL;
        int err = -ENOMEM;

        DBGEV("(hw_config=0x%p)\n", hw_config);

        devc = kmalloc(sizeof (vwsnd_dev_t), GFP_KERNEL);
        if (devc == NULL)
                goto fail0;

        err = li_create(&devc->lith, hw_config->io_base);
        if (err)
                goto fail1;

        init_waitqueue_head(&devc->open_wait);

        devc->rport.hwbuf_size = HWBUF_SIZE;
        devc->rport.hwbuf_vaddr = __get_free_pages(GFP_KERNEL, HWBUF_ORDER);
        if (!devc->rport.hwbuf_vaddr)
                goto fail2;
        devc->rport.hwbuf = (void *) devc->rport.hwbuf_vaddr;
        devc->rport.hwbuf_paddr = virt_to_phys(devc->rport.hwbuf);

        /*
         * Quote from the NT driver:
         *
         * // WARNING!!! HACK to setup output dma!!!
         * // This is required because even on output there is some data
         * // trickling into the input DMA channel.  This is a bug in the
         * // Lithium microcode.
         * // --sde
         *
         * We set the input side's DMA base address here.  It will remain
         * valid until the driver is unloaded.
         */

        li_writel(&devc->lith, LI_COMM1_BASE,
                  devc->rport.hwbuf_paddr >> 8 | 1 << (37 - 8));

        devc->wport.hwbuf_size = HWBUF_SIZE;
        devc->wport.hwbuf_vaddr = __get_free_pages(GFP_KERNEL, HWBUF_ORDER);
        if (!devc->wport.hwbuf_vaddr)
                goto fail3;
        devc->wport.hwbuf = (void *) devc->wport.hwbuf_vaddr;
        devc->wport.hwbuf_paddr = virt_to_phys(devc->wport.hwbuf);
        DBGP("wport hwbuf = 0x%p\n", devc->wport.hwbuf);

        DBGDO(shut_up++);
        err = ad1843_init(&devc->lith);
        DBGDO(shut_up--);
        if (err)
                goto fail4;

        /* install interrupt handler */

        err = request_irq(hw_config->irq, vwsnd_audio_intr, 0, "vwsnd", devc);
        if (err)
                goto fail5;

        /* register this device's drivers. */

        devc->audio_minor = register_sound_dsp(&vwsnd_audio_fops, -1);
        if ((err = devc->audio_minor) < 0) {
                DBGDO(printk(KERN_WARNING
                             "attach_vwsnd: register_sound_dsp error %d\n",
                             err));
                goto fail6;
        }
        devc->mixer_minor = register_sound_mixer(&vwsnd_mixer_fops,
                                                 devc->audio_minor >> 4);
        if ((err = devc->mixer_minor) < 0) {
                DBGDO(printk(KERN_WARNING
                             "attach_vwsnd: register_sound_mixer error %d\n",
                             err));
                goto fail7;
        }

        /* Squirrel away device indices for unload routine. */

        hw_config->slots[0] = devc->audio_minor;

        /* Initialize as much of *devc as possible */

        mutex_init(&devc->open_mutex);
        mutex_init(&devc->io_mutex);
        mutex_init(&devc->mix_mutex);
        devc->open_mode = 0;
        spin_lock_init(&devc->rport.lock);
        init_waitqueue_head(&devc->rport.queue);
        devc->rport.swstate = SW_OFF;
        devc->rport.hwstate = HW_STOPPED;
        devc->rport.flags = 0;
        devc->rport.swbuf = NULL;
        spin_lock_init(&devc->wport.lock);
        init_waitqueue_head(&devc->wport.queue);
        devc->wport.swstate = SW_OFF;
        devc->wport.hwstate = HW_STOPPED;
        devc->wport.flags = 0;
        devc->wport.swbuf = NULL;

        /* Success.  Link us onto the local device list. */

        devc->next_dev = vwsnd_dev_list;
        vwsnd_dev_list = devc;
        return devc->audio_minor;

        /* So many ways to fail.  Undo what we did. */

 fail7:
        unregister_sound_dsp(devc->audio_minor);
 fail6:
        free_irq(hw_config->irq, devc);
 fail5:
 fail4:
        free_pages(devc->wport.hwbuf_vaddr, HWBUF_ORDER);
 fail3:
        free_pages(devc->rport.hwbuf_vaddr, HWBUF_ORDER);
 fail2:
        li_destroy(&devc->lith);
 fail1:
        kfree(devc);
 fail0:
        return err;
}

static int __exit unload_vwsnd(struct address_info *hw_config)
{
        vwsnd_dev_t *devc, **devcp;

        DBGE("()\n");

        devcp = &vwsnd_dev_list;
        while ((devc = *devcp)) {
                if (devc->audio_minor == hw_config->slots[0]) {
                        *devcp = devc->next_dev;
                        break;
                }
                devcp = &devc->next_dev;
        }

        if (!devc)
                return -ENODEV;

        unregister_sound_mixer(devc->mixer_minor);
        unregister_sound_dsp(devc->audio_minor);
        free_irq(hw_config->irq, devc);
        free_pages(devc->wport.hwbuf_vaddr, HWBUF_ORDER);
        free_pages(devc->rport.hwbuf_vaddr, HWBUF_ORDER);
        li_destroy(&devc->lith);
        kfree(devc);

        return 0;
}

/*****************************************************************************/
/* initialization and loadable kernel module interface */

static struct address_info the_hw_config = {
        0xFF001000,                     /* lithium phys addr  */
        CO_IRQ(CO_APIC_LI_AUDIO)        /* irq */
};

MODULE_DESCRIPTION("SGI Visual Workstation sound module");
MODULE_AUTHOR("Bob Miller <kbob@sgi.com>");
MODULE_LICENSE("GPL");

static int __init init_vwsnd(void)
{
        int err;

        DBGXV("\n");
        DBGXV("sound::vwsnd::init_module()\n");

        if (!probe_vwsnd(&the_hw_config))
                return -ENODEV;

        err = attach_vwsnd(&the_hw_config);
        if (err < 0)
                return err;
        return 0;
}

static void __exit cleanup_vwsnd(void)
{
        DBGX("sound::vwsnd::cleanup_module()\n");

        unload_vwsnd(&the_hw_config);
}

module_init(init_vwsnd);
module_exit(cleanup_vwsnd);