/*
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 *
 */

#include <linux/gfp.h>
#include <linux/init.h>
#include <linux/ratelimit.h>
#include <linux/usb.h>
#include <linux/usb/audio.h>

#include <sound/core.h>
#include <sound/pcm.h>

#include "usbaudio.h"
#include "helper.h"
#include "card.h"
#include "endpoint.h"
#include "pcm.h"

/*
 * convert a sampling rate into our full speed format (fs/1000 in Q16.16)
 * this will overflow at approx 524 kHz
 */
static inline unsigned get_usb_full_speed_rate(unsigned int rate)
{
        return ((rate << 13) + 62) / 125;
}

/*
 * convert a sampling rate into USB high speed format (fs/8000 in Q16.16)
 * this will overflow at approx 4 MHz
 */
static inline unsigned get_usb_high_speed_rate(unsigned int rate)
{
        return ((rate << 10) + 62) / 125;
}

/*
 * unlink active urbs.
 */
static int deactivate_urbs(struct snd_usb_substream *subs, int force, int can_sleep)
{
        struct snd_usb_audio *chip = subs->stream->chip;
        unsigned int i;
        int async;

        subs->running = 0;

        if (!force && subs->stream->chip->shutdown) /* to be sure... */
                return -EBADFD;

        async = !can_sleep && chip->async_unlink;

        if (!async && in_interrupt())
                return 0;

        for (i = 0; i < subs->nurbs; i++) {
                if (test_bit(i, &subs->active_mask)) {
                        if (!test_and_set_bit(i, &subs->unlink_mask)) {
                                struct urb *u = subs->dataurb[i].urb;
                                if (async)
                                        usb_unlink_urb(u);
                                else
                                        usb_kill_urb(u);
                        }
                }
        }
        if (subs->syncpipe) {
                for (i = 0; i < SYNC_URBS; i++) {
                        if (test_bit(i+16, &subs->active_mask)) {
                                if (!test_and_set_bit(i+16, &subs->unlink_mask)) {
                                        struct urb *u = subs->syncurb[i].urb;
                                        if (async)
                                                usb_unlink_urb(u);
                                        else
                                                usb_kill_urb(u);
                                }
                        }
                }
        }
        return 0;
}


/*
 * release a urb data
 */
static void release_urb_ctx(struct snd_urb_ctx *u)
{
        if (u->urb) {
                if (u->buffer_size)
                        usb_free_coherent(u->subs->dev, u->buffer_size,
                                        u->urb->transfer_buffer,
                                        u->urb->transfer_dma);
                usb_free_urb(u->urb);
                u->urb = NULL;
        }
}

/*
 *  wait until all urbs are processed.
 */
static int wait_clear_urbs(struct snd_usb_substream *subs)
{
        unsigned long end_time = jiffies + msecs_to_jiffies(1000);
        unsigned int i;
        int alive;

        do {
                alive = 0;
                for (i = 0; i < subs->nurbs; i++) {
                        if (test_bit(i, &subs->active_mask))
                                alive++;
                }
                if (subs->syncpipe) {
                        for (i = 0; i < SYNC_URBS; i++) {
                                if (test_bit(i + 16, &subs->active_mask))
                                        alive++;
                        }
                }
                if (! alive)
                        break;
                schedule_timeout_uninterruptible(1);
        } while (time_before(jiffies, end_time));
        if (alive)
                snd_printk(KERN_ERR "timeout: still %d active urbs..\n", alive);
        return 0;
}

/*
 * release a substream
 */
void snd_usb_release_substream_urbs(struct snd_usb_substream *subs, int force)
{
        int i;

        /* stop urbs (to be sure) */
        deactivate_urbs(subs, force, 1);
        wait_clear_urbs(subs);

        for (i = 0; i < MAX_URBS; i++)
                release_urb_ctx(&subs->dataurb[i]);
        for (i = 0; i < SYNC_URBS; i++)
                release_urb_ctx(&subs->syncurb[i]);
        usb_free_coherent(subs->dev, SYNC_URBS * 4,
                        subs->syncbuf, subs->sync_dma);
        subs->syncbuf = NULL;
        subs->nurbs = 0;
}

/*
 * complete callback from data urb
 */
static void snd_complete_urb(struct urb *urb)
{
        struct snd_urb_ctx *ctx = urb->context;
        struct snd_usb_substream *subs = ctx->subs;
        struct snd_pcm_substream *substream = ctx->subs->pcm_substream;
        int err = 0;

        if ((subs->running && subs->ops.retire(subs, substream->runtime, urb)) ||
            !subs->running || /* can be stopped during retire callback */
            (err = subs->ops.prepare(subs, substream->runtime, urb)) < 0 ||
            (err = usb_submit_urb(urb, GFP_ATOMIC)) < 0) {
                clear_bit(ctx->index, &subs->active_mask);
                if (err < 0) {
                        snd_printd(KERN_ERR "cannot submit urb (err = %d)\n", err);
                        snd_pcm_stop(substream, SNDRV_PCM_STATE_XRUN);
                }
        }
}


/*
 * complete callback from sync urb
 */
static void snd_complete_sync_urb(struct urb *urb)
{
        struct snd_urb_ctx *ctx = urb->context;
        struct snd_usb_substream *subs = ctx->subs;
        struct snd_pcm_substream *substream = ctx->subs->pcm_substream;
        int err = 0;

        if ((subs->running && subs->ops.retire_sync(subs, substream->runtime, urb)) ||
            !subs->running || /* can be stopped during retire callback */
            (err = subs->ops.prepare_sync(subs, substream->runtime, urb)) < 0 ||
            (err = usb_submit_urb(urb, GFP_ATOMIC)) < 0) {
                clear_bit(ctx->index + 16, &subs->active_mask);
                if (err < 0) {
                        snd_printd(KERN_ERR "cannot submit sync urb (err = %d)\n", err);
                        snd_pcm_stop(substream, SNDRV_PCM_STATE_XRUN);
                }
        }
}


/*
 * initialize a substream for plaback/capture
 */
int snd_usb_init_substream_urbs(struct snd_usb_substream *subs,
                                unsigned int period_bytes,
                                unsigned int rate,
                                unsigned int frame_bits)
{
        unsigned int maxsize, i;
        int is_playback = subs->direction == SNDRV_PCM_STREAM_PLAYBACK;
        unsigned int urb_packs, total_packs, packs_per_ms;
        struct snd_usb_audio *chip = subs->stream->chip;

        /* calculate the frequency in 16.16 format */
        if (snd_usb_get_speed(subs->dev) == USB_SPEED_FULL)
                subs->freqn = get_usb_full_speed_rate(rate);
        else
                subs->freqn = get_usb_high_speed_rate(rate);
        subs->freqm = subs->freqn;
        subs->freqshift = INT_MIN;
        /* calculate max. frequency */
        if (subs->maxpacksize) {
                /* whatever fits into a max. size packet */
                maxsize = subs->maxpacksize;
                subs->freqmax = (maxsize / (frame_bits >> 3))
                                << (16 - subs->datainterval);
        } else {
                /* no max. packet size: just take 25% higher than nominal */
                subs->freqmax = subs->freqn + (subs->freqn >> 2);
                maxsize = ((subs->freqmax + 0xffff) * (frame_bits >> 3))
                                >> (16 - subs->datainterval);
        }
        subs->phase = 0;

        if (subs->fill_max)
                subs->curpacksize = subs->maxpacksize;
        else
                subs->curpacksize = maxsize;

        if (snd_usb_get_speed(subs->dev) != USB_SPEED_FULL)
                packs_per_ms = 8 >> subs->datainterval;
        else
                packs_per_ms = 1;

        if (is_playback) {
                urb_packs = max(chip->nrpacks, 1);
                urb_packs = min(urb_packs, (unsigned int)MAX_PACKS);
        } else
                urb_packs = 1;
        urb_packs *= packs_per_ms;
        if (subs->syncpipe)
                urb_packs = min(urb_packs, 1U << subs->syncinterval);

        /* decide how many packets to be used */
        if (is_playback) {
                unsigned int minsize, maxpacks;
                /* determine how small a packet can be */
                minsize = (subs->freqn >> (16 - subs->datainterval))
                          * (frame_bits >> 3);
                /* with sync from device, assume it can be 12% lower */
                if (subs->syncpipe)
                        minsize -= minsize >> 3;
                minsize = max(minsize, 1u);
                total_packs = (period_bytes + minsize - 1) / minsize;
                /* we need at least two URBs for queueing */
                if (total_packs < 2) {
                        total_packs = 2;
                } else {
                        /* and we don't want too long a queue either */
                        maxpacks = max(MAX_QUEUE * packs_per_ms, urb_packs * 2);
                        total_packs = min(total_packs, maxpacks);
                }
        } else {
                while (urb_packs > 1 && urb_packs * maxsize >= period_bytes)
                        urb_packs >>= 1;
                total_packs = MAX_URBS * urb_packs;
        }
        subs->nurbs = (total_packs + urb_packs - 1) / urb_packs;
        if (subs->nurbs > MAX_URBS) {
                /* too much... */
                subs->nurbs = MAX_URBS;
                total_packs = MAX_URBS * urb_packs;
        } else if (subs->nurbs < 2) {
                /* too little - we need at least two packets
                 * to ensure contiguous playback/capture
                 */
                subs->nurbs = 2;
        }

        /* allocate and initialize data urbs */
        for (i = 0; i < subs->nurbs; i++) {
                struct snd_urb_ctx *u = &subs->dataurb[i];
                u->index = i;
                u->subs = subs;
                u->packets = (i + 1) * total_packs / subs->nurbs
                        - i * total_packs / subs->nurbs;
                u->buffer_size = maxsize * u->packets;
                if (subs->fmt_type == UAC_FORMAT_TYPE_II)
                        u->packets++; /* for transfer delimiter */
                u->urb = usb_alloc_urb(u->packets, GFP_KERNEL);
                if (!u->urb)
                        goto out_of_memory;
                u->urb->transfer_buffer =
                        usb_alloc_coherent(subs->dev, u->buffer_size,
                                           GFP_KERNEL, &u->urb->transfer_dma);
                if (!u->urb->transfer_buffer)
                        goto out_of_memory;
                u->urb->pipe = subs->datapipe;
                u->urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;
                u->urb->interval = 1 << subs->datainterval;
                u->urb->context = u;
                u->urb->complete = snd_complete_urb;
        }

        if (subs->syncpipe) {
                /* allocate and initialize sync urbs */
                subs->syncbuf = usb_alloc_coherent(subs->dev, SYNC_URBS * 4,
                                                 GFP_KERNEL, &subs->sync_dma);
                if (!subs->syncbuf)
                        goto out_of_memory;
                for (i = 0; i < SYNC_URBS; i++) {
                        struct snd_urb_ctx *u = &subs->syncurb[i];
                        u->index = i;
                        u->subs = subs;
                        u->packets = 1;
                        u->urb = usb_alloc_urb(1, GFP_KERNEL);
                        if (!u->urb)
                                goto out_of_memory;
                        u->urb->transfer_buffer = subs->syncbuf + i * 4;
                        u->urb->transfer_dma = subs->sync_dma + i * 4;
                        u->urb->transfer_buffer_length = 4;
                        u->urb->pipe = subs->syncpipe;
                        u->urb->transfer_flags = URB_ISO_ASAP |
                                                 URB_NO_TRANSFER_DMA_MAP;
                        u->urb->number_of_packets = 1;
                        u->urb->interval = 1 << subs->syncinterval;
                        u->urb->context = u;
                        u->urb->complete = snd_complete_sync_urb;
                }
        }
        return 0;

out_of_memory:
        snd_usb_release_substream_urbs(subs, 0);
        return -ENOMEM;
}

/*
 * prepare urb for full speed capture sync pipe
 *
 * fill the length and offset of each urb descriptor.
 * the fixed 10.14 frequency is passed through the pipe.
 */
static int prepare_capture_sync_urb(struct snd_usb_substream *subs,
                                    struct snd_pcm_runtime *runtime,
                                    struct urb *urb)
{
        unsigned char *cp = urb->transfer_buffer;
        struct snd_urb_ctx *ctx = urb->context;

        urb->dev = ctx->subs->dev; /* we need to set this at each time */
        urb->iso_frame_desc[0].length = 3;
        urb->iso_frame_desc[0].offset = 0;
        cp[0] = subs->freqn >> 2;
        cp[1] = subs->freqn >> 10;
        cp[2] = subs->freqn >> 18;
        return 0;
}

/*
 * prepare urb for high speed capture sync pipe
 *
 * fill the length and offset of each urb descriptor.
 * the fixed 12.13 frequency is passed as 16.16 through the pipe.
 */
static int prepare_capture_sync_urb_hs(struct snd_usb_substream *subs,
                                       struct snd_pcm_runtime *runtime,
                                       struct urb *urb)
{
        unsigned char *cp = urb->transfer_buffer;
        struct snd_urb_ctx *ctx = urb->context;

        urb->dev = ctx->subs->dev; /* we need to set this at each time */
        urb->iso_frame_desc[0].length = 4;
        urb->iso_frame_desc[0].offset = 0;
        cp[0] = subs->freqn;
        cp[1] = subs->freqn >> 8;
        cp[2] = subs->freqn >> 16;
        cp[3] = subs->freqn >> 24;
        return 0;
}

/*
 * process after capture sync complete
 * - nothing to do
 */
static int retire_capture_sync_urb(struct snd_usb_substream *subs,
                                   struct snd_pcm_runtime *runtime,
                                   struct urb *urb)
{
        return 0;
}

/*
 * prepare urb for capture data pipe
 *
 * fill the offset and length of each descriptor.
 *
 * we use a temporary buffer to write the captured data.
 * since the length of written data is determined by host, we cannot
 * write onto the pcm buffer directly...  the data is thus copied
 * later at complete callback to the global buffer.
 */
static int prepare_capture_urb(struct snd_usb_substream *subs,
                               struct snd_pcm_runtime *runtime,
                               struct urb *urb)
{
        int i, offs;
        struct snd_urb_ctx *ctx = urb->context;

        offs = 0;
        urb->dev = ctx->subs->dev; /* we need to set this at each time */
        for (i = 0; i < ctx->packets; i++) {
                urb->iso_frame_desc[i].offset = offs;
                urb->iso_frame_desc[i].length = subs->curpacksize;
                offs += subs->curpacksize;
        }
        urb->transfer_buffer_length = offs;
        urb->number_of_packets = ctx->packets;
        return 0;
}

/*
 * process after capture complete
 *
 * copy the data from each desctiptor to the pcm buffer, and
 * update the current position.
 */
static int retire_capture_urb(struct snd_usb_substream *subs,
                              struct snd_pcm_runtime *runtime,
                              struct urb *urb)
{
        unsigned long flags;
        unsigned char *cp;
        int i;
        unsigned int stride, frames, bytes, oldptr;
        int period_elapsed = 0;

        stride = runtime->frame_bits >> 3;

        for (i = 0; i < urb->number_of_packets; i++) {
                cp = (unsigned char *)urb->transfer_buffer + urb->iso_frame_desc[i].offset;
                if (urb->iso_frame_desc[i].status && printk_ratelimit()) {
                        snd_printdd("frame %d active: %d\n", i, urb->iso_frame_desc[i].status);
                        // continue;
                }
                bytes = urb->iso_frame_desc[i].actual_length;
                frames = bytes / stride;
                if (!subs->txfr_quirk)
                        bytes = frames * stride;
                if (bytes % (runtime->sample_bits >> 3) != 0) {
#ifdef CONFIG_SND_DEBUG_VERBOSE
                        int oldbytes = bytes;
#endif
                        bytes = frames * stride;
                        snd_printdd(KERN_ERR "Corrected urb data len. %d->%d\n",
                                                        oldbytes, bytes);
                }
                /* update the current pointer */
                spin_lock_irqsave(&subs->lock, flags);
                oldptr = subs->hwptr_done;
                subs->hwptr_done += bytes;
                if (subs->hwptr_done >= runtime->buffer_size * stride)
                        subs->hwptr_done -= runtime->buffer_size * stride;
                frames = (bytes + (oldptr % stride)) / stride;
                subs->transfer_done += frames;
                if (subs->transfer_done >= runtime->period_size) {
                        subs->transfer_done -= runtime->period_size;
                        period_elapsed = 1;
                }
                spin_unlock_irqrestore(&subs->lock, flags);
                /* copy a data chunk */
                if (oldptr + bytes > runtime->buffer_size * stride) {
                        unsigned int bytes1 =
                                        runtime->buffer_size * stride - oldptr;
                        memcpy(runtime->dma_area + oldptr, cp, bytes1);
                        memcpy(runtime->dma_area, cp + bytes1, bytes - bytes1);
                } else {
                        memcpy(runtime->dma_area + oldptr, cp, bytes);
                }
        }
        if (period_elapsed)
                snd_pcm_period_elapsed(subs->pcm_substream);
        return 0;
}

/*
 * Process after capture complete when paused.  Nothing to do.
 */
static int retire_paused_capture_urb(struct snd_usb_substream *subs,
                                     struct snd_pcm_runtime *runtime,
                                     struct urb *urb)
{
        return 0;
}


/*
 * prepare urb for playback sync pipe
 *
 * set up the offset and length to receive the current frequency.
 */
static int prepare_playback_sync_urb(struct snd_usb_substream *subs,
                                     struct snd_pcm_runtime *runtime,
                                     struct urb *urb)
{
        struct snd_urb_ctx *ctx = urb->context;

        urb->dev = ctx->subs->dev; /* we need to set this at each time */
        urb->iso_frame_desc[0].length = min(4u, ctx->subs->syncmaxsize);
        urb->iso_frame_desc[0].offset = 0;
        return 0;
}

/*
 * process after playback sync complete
 *
 * Full speed devices report feedback values in 10.14 format as samples per
 * frame, high speed devices in 16.16 format as samples per microframe.
 * Because the Audio Class 1 spec was written before USB 2.0, many high speed
 * devices use a wrong interpretation, some others use an entirely different
 * format.  Therefore, we cannot predict what format any particular device uses
 * and must detect it automatically.
 */
static int retire_playback_sync_urb(struct snd_usb_substream *subs,
                                    struct snd_pcm_runtime *runtime,
                                    struct urb *urb)
{
        unsigned int f;
        int shift;
        unsigned long flags;

        if (urb->iso_frame_desc[0].status != 0 ||
            urb->iso_frame_desc[0].actual_length < 3)
                return 0;

        f = le32_to_cpup(urb->transfer_buffer);
        if (urb->iso_frame_desc[0].actual_length == 3)
                f &= 0x00ffffff;
        else
                f &= 0x0fffffff;
        if (f == 0)
                return 0;

        if (unlikely(subs->freqshift == INT_MIN)) {
                /*
                 * The first time we see a feedback value, determine its format
                 * by shifting it left or right until it matches the nominal
                 * frequency value.  This assumes that the feedback does not
                 * differ from the nominal value more than +50% or -25%.
                 */
                shift = 0;
                while (f < subs->freqn - subs->freqn / 4) {
                        f <<= 1;
                        shift++;
                }
                while (f > subs->freqn + subs->freqn / 2) {
                        f >>= 1;
                        shift--;
                }
                subs->freqshift = shift;
        }
        else if (subs->freqshift >= 0)
                f <<= subs->freqshift;
        else
                f >>= -subs->freqshift;

        if (likely(f >= subs->freqn - subs->freqn / 8 && f <= subs->freqmax)) {
                /*
                 * If the frequency looks valid, set it.
                 * This value is referred to in prepare_playback_urb().
                 */
                spin_lock_irqsave(&subs->lock, flags);
                subs->freqm = f;
                spin_unlock_irqrestore(&subs->lock, flags);
        } else {
                /*
                 * Out of range; maybe the shift value is wrong.
                 * Reset it so that we autodetect again the next time.
                 */
                subs->freqshift = INT_MIN;
        }

        return 0;
}

/* determine the number of frames in the next packet */
static int snd_usb_audio_next_packet_size(struct snd_usb_substream *subs)
{
        if (subs->fill_max)
                return subs->maxframesize;
        else {
                subs->phase = (subs->phase & 0xffff)
                        + (subs->freqm << subs->datainterval);
                return min(subs->phase >> 16, subs->maxframesize);
        }
}

/*
 * Prepare urb for streaming before playback starts or when paused.
 *
 * We don't have any data, so we send silence.
 */
static int prepare_nodata_playback_urb(struct snd_usb_substream *subs,
                                       struct snd_pcm_runtime *runtime,
                                       struct urb *urb)
{
        unsigned int i, offs, counts;
        struct snd_urb_ctx *ctx = urb->context;
        int stride = runtime->frame_bits >> 3;

        offs = 0;
        urb->dev = ctx->subs->dev;
        for (i = 0; i < ctx->packets; ++i) {
                counts = snd_usb_audio_next_packet_size(subs);
                urb->iso_frame_desc[i].offset = offs * stride;
                urb->iso_frame_desc[i].length = counts * stride;
                offs += counts;
        }
        urb->number_of_packets = ctx->packets;
        urb->transfer_buffer_length = offs * stride;
        memset(urb->transfer_buffer,
               runtime->format == SNDRV_PCM_FORMAT_U8 ? 0x80 : 0,
               offs * stride);
        return 0;
}

/*
 * prepare urb for playback data pipe
 *
 * Since a URB can handle only a single linear buffer, we must use double
 * buffering when the data to be transferred overflows the buffer boundary.
 * To avoid inconsistencies when updating hwptr_done, we use double buffering
 * for all URBs.
 */
static int prepare_playback_urb(struct snd_usb_substream *subs,
                                struct snd_pcm_runtime *runtime,
                                struct urb *urb)
{
        int i, stride;
        unsigned int counts, frames, bytes;
        unsigned long flags;
        int period_elapsed = 0;
        struct snd_urb_ctx *ctx = urb->context;

        stride = runtime->frame_bits >> 3;

        frames = 0;
        urb->dev = ctx->subs->dev; /* we need to set this at each time */
        urb->number_of_packets = 0;
        spin_lock_irqsave(&subs->lock, flags);
        for (i = 0; i < ctx->packets; i++) {
                counts = snd_usb_audio_next_packet_size(subs);
                /* set up descriptor */
                urb->iso_frame_desc[i].offset = frames * stride;
                urb->iso_frame_desc[i].length = counts * stride;
                frames += counts;
                urb->number_of_packets++;
                subs->transfer_done += counts;
                if (subs->transfer_done >= runtime->period_size) {
                        subs->transfer_done -= runtime->period_size;
                        period_elapsed = 1;
                        if (subs->fmt_type == UAC_FORMAT_TYPE_II) {
                                if (subs->transfer_done > 0) {
                                        /* FIXME: fill-max mode is not
                                         * supported yet */
                                        frames -= subs->transfer_done;
                                        counts -= subs->transfer_done;
                                        urb->iso_frame_desc[i].length =
                                                counts * stride;
                                        subs->transfer_done = 0;
                                }
                                i++;
                                if (i < ctx->packets) {
                                        /* add a transfer delimiter */
                                        urb->iso_frame_desc[i].offset =
                                                frames * stride;
                                        urb->iso_frame_desc[i].length = 0;
                                        urb->number_of_packets++;
                                }
                                break;
                        }
                }
                if (period_elapsed) /* finish at the period boundary */
                        break;
        }
        bytes = frames * stride;
        if (subs->hwptr_done + bytes > runtime->buffer_size * stride) {
                /* err, the transferred area goes over buffer boundary. */
                unsigned int bytes1 =
                        runtime->buffer_size * stride - subs->hwptr_done;
                memcpy(urb->transfer_buffer,
                       runtime->dma_area + subs->hwptr_done, bytes1);
                memcpy(urb->transfer_buffer + bytes1,
                       runtime->dma_area, bytes - bytes1);
        } else {
                memcpy(urb->transfer_buffer,
                       runtime->dma_area + subs->hwptr_done, bytes);
        }
        subs->hwptr_done += bytes;
        if (subs->hwptr_done >= runtime->buffer_size * stride)
                subs->hwptr_done -= runtime->buffer_size * stride;

        /* update delay with exact number of samples queued */
        runtime->delay = subs->last_delay;
        runtime->delay += frames;
        subs->last_delay = runtime->delay;

        /* realign last_frame_number */
        subs->last_frame_number = usb_get_current_frame_number(subs->dev);
        subs->last_frame_number &= 0xFF; /* keep 8 LSBs */

        spin_unlock_irqrestore(&subs->lock, flags);
        urb->transfer_buffer_length = bytes;
        if (period_elapsed)
                snd_pcm_period_elapsed(subs->pcm_substream);
        return 0;
}

/*
 * process after playback data complete
 * - decrease the delay count again
 */
static int retire_playback_urb(struct snd_usb_substream *subs,
                               struct snd_pcm_runtime *runtime,
                               struct urb *urb)
{
        unsigned long flags;
        int stride = runtime->frame_bits >> 3;
        int processed = urb->transfer_buffer_length / stride;
        int est_delay;

        spin_lock_irqsave(&subs->lock, flags);

        est_delay = snd_usb_pcm_delay(subs, runtime->rate);
        /* update delay with exact number of samples played */
        if (processed > subs->last_delay)
                subs->last_delay = 0;
        else
                subs->last_delay -= processed;
        runtime->delay = subs->last_delay;

        /*
         * Report when delay estimate is off by more than 2ms.
         * The error should be lower than 2ms since the estimate relies
         * on two reads of a counter updated every ms.
         */
        if (abs(est_delay - subs->last_delay) * 1000 > runtime->rate * 2)
                snd_printk(KERN_DEBUG "delay: estimated %d, actual %d\n",
                        est_delay, subs->last_delay);

        spin_unlock_irqrestore(&subs->lock, flags);
        return 0;
}

static const char *usb_error_string(int err)
{
        switch (err) {
        case -ENODEV:
                return "no device";
        case -ENOENT:
                return "endpoint not enabled";
        case -EPIPE:
                return "endpoint stalled";
        case -ENOSPC:
                return "not enough bandwidth";
        case -ESHUTDOWN:
                return "device disabled";
        case -EHOSTUNREACH:
                return "device suspended";
        case -EINVAL:
        case -EAGAIN:
        case -EFBIG:
        case -EMSGSIZE:
                return "internal error";
        default:
                return "unknown error";
        }
}

/*
 * set up and start data/sync urbs
 */
static int start_urbs(struct snd_usb_substream *subs, struct snd_pcm_runtime *runtime)
{
        unsigned int i;
        int err;

        if (subs->stream->chip->shutdown)
                return -EBADFD;

        for (i = 0; i < subs->nurbs; i++) {
                if (snd_BUG_ON(!subs->dataurb[i].urb))
                        return -EINVAL;
                if (subs->ops.prepare(subs, runtime, subs->dataurb[i].urb) < 0) {
                        snd_printk(KERN_ERR "cannot prepare datapipe for urb %d\n", i);
                        goto __error;
                }
        }
        if (subs->syncpipe) {
                for (i = 0; i < SYNC_URBS; i++) {
                        if (snd_BUG_ON(!subs->syncurb[i].urb))
                                return -EINVAL;
                        if (subs->ops.prepare_sync(subs, runtime, subs->syncurb[i].urb) < 0) {
                                snd_printk(KERN_ERR "cannot prepare syncpipe for urb %d\n", i);
                                goto __error;
                        }
                }
        }

        subs->active_mask = 0;
        subs->unlink_mask = 0;
        subs->running = 1;
        for (i = 0; i < subs->nurbs; i++) {
                err = usb_submit_urb(subs->dataurb[i].urb, GFP_ATOMIC);
                if (err < 0) {
                        snd_printk(KERN_ERR "cannot submit datapipe "
                                   "for urb %d, error %d: %s\n",
                                   i, err, usb_error_string(err));
                        goto __error;
                }
                set_bit(i, &subs->active_mask);
        }
        if (subs->syncpipe) {
                for (i = 0; i < SYNC_URBS; i++) {
                        err = usb_submit_urb(subs->syncurb[i].urb, GFP_ATOMIC);
                        if (err < 0) {
                                snd_printk(KERN_ERR "cannot submit syncpipe "
                                           "for urb %d, error %d: %s\n",
                                           i, err, usb_error_string(err));
                                goto __error;
                        }
                        set_bit(i + 16, &subs->active_mask);
                }
        }
        return 0;

 __error:
        // snd_pcm_stop(subs->pcm_substream, SNDRV_PCM_STATE_XRUN);
        deactivate_urbs(subs, 0, 0);
        return -EPIPE;
}


/*
 */
static struct snd_urb_ops audio_urb_ops[2] = {
        {
                .prepare =      prepare_nodata_playback_urb,
                .retire =       retire_playback_urb,
                .prepare_sync = prepare_playback_sync_urb,
                .retire_sync =  retire_playback_sync_urb,
        },
        {
                .prepare =      prepare_capture_urb,
                .retire =       retire_capture_urb,
                .prepare_sync = prepare_capture_sync_urb,
                .retire_sync =  retire_capture_sync_urb,
        },
};

/*
 * initialize the substream instance.
 */

void snd_usb_init_substream(struct snd_usb_stream *as,
                            int stream, struct audioformat *fp)
{
        struct snd_usb_substream *subs = &as->substream[stream];

        INIT_LIST_HEAD(&subs->fmt_list);
        spin_lock_init(&subs->lock);

        subs->stream = as;
        subs->direction = stream;
        subs->dev = as->chip->dev;
        subs->txfr_quirk = as->chip->txfr_quirk;
        subs->ops = audio_urb_ops[stream];
        if (snd_usb_get_speed(subs->dev) >= USB_SPEED_HIGH)
                subs->ops.prepare_sync = prepare_capture_sync_urb_hs;

        snd_usb_set_pcm_ops(as->pcm, stream);

        list_add_tail(&fp->list, &subs->fmt_list);
        subs->formats |= fp->formats;
        subs->endpoint = fp->endpoint;
        subs->num_formats++;
        subs->fmt_type = fp->fmt_type;
}

int snd_usb_substream_playback_trigger(struct snd_pcm_substream *substream, int cmd)
{
        struct snd_usb_substream *subs = substream->runtime->private_data;

        switch (cmd) {
        case SNDRV_PCM_TRIGGER_START:
        case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
                subs->ops.prepare = prepare_playback_urb;
                return 0;
        case SNDRV_PCM_TRIGGER_STOP:
                return deactivate_urbs(subs, 0, 0);
        case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
                subs->ops.prepare = prepare_nodata_playback_urb;
                return 0;
        }

        return -EINVAL;
}

int snd_usb_substream_capture_trigger(struct snd_pcm_substream *substream, int cmd)
{
        struct snd_usb_substream *subs = substream->runtime->private_data;

        switch (cmd) {
        case SNDRV_PCM_TRIGGER_START:
                subs->ops.retire = retire_capture_urb;
                return start_urbs(subs, substream->runtime);
        case SNDRV_PCM_TRIGGER_STOP:
                return deactivate_urbs(subs, 0, 0);
        case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
                subs->ops.retire = retire_paused_capture_urb;
                return 0;
        case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
                subs->ops.retire = retire_capture_urb;
                return 0;
        }

        return -EINVAL;
}

int snd_usb_substream_prepare(struct snd_usb_substream *subs,
                              struct snd_pcm_runtime *runtime)
{
        /* clear urbs (to be sure) */
        deactivate_urbs(subs, 0, 1);
        wait_clear_urbs(subs);

        /* for playback, submit the URBs now; otherwise, the first hwptr_done
         * updates for all URBs would happen at the same time when starting */
        if (subs->direction == SNDRV_PCM_STREAM_PLAYBACK) {
                subs->ops.prepare = prepare_nodata_playback_urb;
                return start_urbs(subs, runtime);
        }

        return 0;
}