endpoint.c

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/*
 *   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 <linux/slab.h>

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

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

#define EP_FLAG_ACTIVATED   0
#define EP_FLAG_RUNNING     1
#define EP_FLAG_STOPPING    2

/*
 * snd_usb_endpoint is a model that abstracts everything related to an
 * USB endpoint and its streaming.
 *
 * There are functions to activate and deactivate the streaming URBs and
 * optional callbacks to let the pcm logic handle the actual content of the
 * packets for playback and record. Thus, the bus streaming and the audio
 * handlers are fully decoupled.
 *
 * There are two different types of endpoints in audio applications.
 *
 * SND_USB_ENDPOINT_TYPE_DATA handles full audio data payload for both
 * inbound and outbound traffic.
 *
 * SND_USB_ENDPOINT_TYPE_SYNC endpoints are for inbound traffic only and
 * expect the payload to carry Q10.14 / Q16.16 formatted sync information
 * (3 or 4 bytes).
 *
 * Each endpoint has to be configured prior to being used by calling
 * snd_usb_endpoint_set_params().
 *
 * The model incorporates a reference counting, so that multiple users
 * can call snd_usb_endpoint_start() and snd_usb_endpoint_stop(), and
 * only the first user will effectively start the URBs, and only the last
 * one to stop it will tear the URBs down again.
 */

/*
 * 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;
}

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

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";
    }
}

int snd_usb_endpoint_implict_feedback_sink(struct snd_usb_endpoint *ep)
{
    return  ep->sync_master &&
        ep->sync_master->type == SND_USB_ENDPOINT_TYPE_DATA &&
        ep->type == SND_USB_ENDPOINT_TYPE_DATA &&
        usb_pipeout(ep->pipe);
}

/*
 * For streaming based on information derived from sync endpoints,
 * prepare_outbound_urb_sizes() will call next_packet_size() to
 * determine the number of samples to be sent in the next packet.
 *
 * For implicit feedback, next_packet_size() is unused.
 */
int snd_usb_endpoint_next_packet_size(struct snd_usb_endpoint *ep)
{
    unsigned long flags;
    int ret;

    if (ep->fill_max)
        return ep->maxframesize;

    spin_lock_irqsave(&ep->lock, flags);
    ep->phase = (ep->phase & 0xffff)
        + (ep->freqm << ep->datainterval);
    ret = min(ep->phase >> 16, ep->maxframesize);
    spin_unlock_irqrestore(&ep->lock, flags);

    return ret;
}

static void retire_outbound_urb(struct snd_usb_endpoint *ep,
                struct snd_urb_ctx *urb_ctx)
{
    if (ep->retire_data_urb)
        ep->retire_data_urb(ep->data_subs, urb_ctx->urb);
}

static void retire_inbound_urb(struct snd_usb_endpoint *ep,
                   struct snd_urb_ctx *urb_ctx)
{
    struct urb *urb = urb_ctx->urb;

    if (unlikely(ep->skip_packets > 0)) {
        ep->skip_packets--;
        return;
    }

    if (ep->sync_slave)
        snd_usb_handle_sync_urb(ep->sync_slave, ep, urb);

    if (ep->retire_data_urb)
        ep->retire_data_urb(ep->data_subs, urb);
}

/*
 * Prepare a PLAYBACK urb for submission to the bus.
 */
static void prepare_outbound_urb(struct snd_usb_endpoint *ep,
                 struct snd_urb_ctx *ctx)
{
    int i;
    struct urb *urb = ctx->urb;
    unsigned char *cp = urb->transfer_buffer;

    urb->dev = ep->chip->dev; /* we need to set this at each time */

    switch (ep->type) {
    case SND_USB_ENDPOINT_TYPE_DATA:
        if (ep->prepare_data_urb) {
            ep->prepare_data_urb(ep->data_subs, urb);
        } else {
            /* no data provider, so send silence */
            unsigned int offs = 0;
            for (i = 0; i < ctx->packets; ++i) {
                int counts;

                if (ctx->packet_size[i])
                    counts = ctx->packet_size[i];
                else
                    counts = snd_usb_endpoint_next_packet_size(ep);

                urb->iso_frame_desc[i].offset = offs * ep->stride;
                urb->iso_frame_desc[i].length = counts * ep->stride;
                offs += counts;
            }

            urb->number_of_packets = ctx->packets;
            urb->transfer_buffer_length = offs * ep->stride;
            memset(urb->transfer_buffer, ep->silence_value,
                   offs * ep->stride);
        }
        break;

    case SND_USB_ENDPOINT_TYPE_SYNC:
        if (snd_usb_get_speed(ep->chip->dev) >= USB_SPEED_HIGH) {
            /*
             * fill the length and offset of each urb descriptor.
             * the fixed 12.13 frequency is passed as 16.16 through the pipe.
             */
            urb->iso_frame_desc[0].length = 4;
            urb->iso_frame_desc[0].offset = 0;
            cp[0] = ep->freqn;
            cp[1] = ep->freqn >> 8;
            cp[2] = ep->freqn >> 16;
            cp[3] = ep->freqn >> 24;
        } else {
            /*
             * fill the length and offset of each urb descriptor.
             * the fixed 10.14 frequency is passed through the pipe.
             */
            urb->iso_frame_desc[0].length = 3;
            urb->iso_frame_desc[0].offset = 0;
            cp[0] = ep->freqn >> 2;
            cp[1] = ep->freqn >> 10;
            cp[2] = ep->freqn >> 18;
        }

        break;
    }
}

/*
 * Prepare a CAPTURE or SYNC urb for submission to the bus.
 */
static inline void prepare_inbound_urb(struct snd_usb_endpoint *ep,
                       struct snd_urb_ctx *urb_ctx)
{
    int i, offs;
    struct urb *urb = urb_ctx->urb;

    urb->dev = ep->chip->dev; /* we need to set this at each time */

    switch (ep->type) {
    case SND_USB_ENDPOINT_TYPE_DATA:
        offs = 0;
        for (i = 0; i < urb_ctx->packets; i++) {
            urb->iso_frame_desc[i].offset = offs;
            urb->iso_frame_desc[i].length = ep->curpacksize;
            offs += ep->curpacksize;
        }

        urb->transfer_buffer_length = offs;
        urb->number_of_packets = urb_ctx->packets;
        break;

    case SND_USB_ENDPOINT_TYPE_SYNC:
        urb->iso_frame_desc[0].length = min(4u, ep->syncmaxsize);
        urb->iso_frame_desc[0].offset = 0;
        break;
    }
}

/*
 * Send output urbs that have been prepared previously. URBs are dequeued
 * from ep->ready_playback_urbs and in case there there aren't any available
 * or there are no packets that have been prepared, this function does
 * nothing.
 *
 * The reason why the functionality of sending and preparing URBs is separated
 * is that host controllers don't guarantee the order in which they return
 * inbound and outbound packets to their submitters.
 *
 * This function is only used for implicit feedback endpoints. For endpoints
 * driven by dedicated sync endpoints, URBs are immediately re-submitted
 * from their completion handler.
 */
static void queue_pending_output_urbs(struct snd_usb_endpoint *ep)
{
    while (test_bit(EP_FLAG_RUNNING, &ep->flags)) {

        unsigned long flags;
        struct snd_usb_packet_info *uninitialized_var(packet);
        struct snd_urb_ctx *ctx = NULL;
        struct urb *urb;
        int err, i;

        spin_lock_irqsave(&ep->lock, flags);
        if (ep->next_packet_read_pos != ep->next_packet_write_pos) {
            packet = ep->next_packet + ep->next_packet_read_pos;
            ep->next_packet_read_pos++;
            ep->next_packet_read_pos %= MAX_URBS;

            /* take URB out of FIFO */
            if (!list_empty(&ep->ready_playback_urbs))
                ctx = list_first_entry(&ep->ready_playback_urbs,
                           struct snd_urb_ctx, ready_list);
        }
        spin_unlock_irqrestore(&ep->lock, flags);

        if (ctx == NULL)
            return;

        list_del_init(&ctx->ready_list);
        urb = ctx->urb;

        /* copy over the length information */
        for (i = 0; i < packet->packets; i++)
            ctx->packet_size[i] = packet->packet_size[i];

        /* call the data handler to fill in playback data */
        prepare_outbound_urb(ep, ctx);

        err = usb_submit_urb(ctx->urb, GFP_ATOMIC);
        if (err < 0)
            snd_printk(KERN_ERR "Unable to submit urb #%d: %d (urb %p)\n",
                   ctx->index, err, ctx->urb);
        else
            set_bit(ctx->index, &ep->active_mask);
    }
}

/*
 * complete callback for urbs
 */
static void snd_complete_urb(struct urb *urb)
{
    struct snd_urb_ctx *ctx = urb->context;
    struct snd_usb_endpoint *ep = ctx->ep;
    int err;

    if (unlikely(urb->status == -ENOENT ||      /* unlinked */
             urb->status == -ENODEV ||      /* device removed */
             urb->status == -ECONNRESET ||  /* unlinked */
             urb->status == -ESHUTDOWN ||   /* device disabled */
             ep->chip->shutdown))       /* device disconnected */
        goto exit_clear;

    if (usb_pipeout(ep->pipe)) {
        retire_outbound_urb(ep, ctx);
        /* can be stopped during retire callback */
        if (unlikely(!test_bit(EP_FLAG_RUNNING, &ep->flags)))
            goto exit_clear;

        if (snd_usb_endpoint_implict_feedback_sink(ep)) {
            unsigned long flags;

            spin_lock_irqsave(&ep->lock, flags);
            list_add_tail(&ctx->ready_list, &ep->ready_playback_urbs);
            spin_unlock_irqrestore(&ep->lock, flags);
            queue_pending_output_urbs(ep);

            goto exit_clear;
        }

        prepare_outbound_urb(ep, ctx);
    } else {
        retire_inbound_urb(ep, ctx);
        /* can be stopped during retire callback */
        if (unlikely(!test_bit(EP_FLAG_RUNNING, &ep->flags)))
            goto exit_clear;

        prepare_inbound_urb(ep, ctx);
    }

    err = usb_submit_urb(urb, GFP_ATOMIC);
    if (err == 0)
        return;

    snd_printk(KERN_ERR "cannot submit urb (err = %d)\n", err);
    //snd_pcm_stop(substream, SNDRV_PCM_STATE_XRUN);

exit_clear:
    clear_bit(ctx->index, &ep->active_mask);
}

struct snd_usb_endpoint *snd_usb_add_endpoint(struct snd_usb_audio *chip,
                          struct usb_host_interface *alts,
                          int ep_num, int direction, int type)
{
    struct list_head *p;
    struct snd_usb_endpoint *ep;
    int is_playback = direction == SNDRV_PCM_STREAM_PLAYBACK;

    mutex_lock(&chip->mutex);

    list_for_each(p, &chip->ep_list) {
        ep = list_entry(p, struct snd_usb_endpoint, list);
        if (ep->ep_num == ep_num &&
            ep->iface == alts->desc.bInterfaceNumber &&
            ep->alt_idx == alts->desc.bAlternateSetting) {
            snd_printdd(KERN_DEBUG "Re-using EP %x in iface %d,%d @%p\n",
                    ep_num, ep->iface, ep->alt_idx, ep);
            goto __exit_unlock;
        }
    }

    snd_printdd(KERN_DEBUG "Creating new %s %s endpoint #%x\n",
            is_playback ? "playback" : "capture",
            type == SND_USB_ENDPOINT_TYPE_DATA ? "data" : "sync",
            ep_num);

    ep = kzalloc(sizeof(*ep), GFP_KERNEL);
    if (!ep)
        goto __exit_unlock;

    ep->chip = chip;
    spin_lock_init(&ep->lock);
    ep->type = type;
    ep->ep_num = ep_num;
    ep->iface = alts->desc.bInterfaceNumber;
    ep->alt_idx = alts->desc.bAlternateSetting;
    INIT_LIST_HEAD(&ep->ready_playback_urbs);
    ep_num &= USB_ENDPOINT_NUMBER_MASK;

    if (is_playback)
        ep->pipe = usb_sndisocpipe(chip->dev, ep_num);
    else
        ep->pipe = usb_rcvisocpipe(chip->dev, ep_num);

    if (type == SND_USB_ENDPOINT_TYPE_SYNC) {
        if (get_endpoint(alts, 1)->bLength >= USB_DT_ENDPOINT_AUDIO_SIZE &&
            get_endpoint(alts, 1)->bRefresh >= 1 &&
            get_endpoint(alts, 1)->bRefresh <= 9)
            ep->syncinterval = get_endpoint(alts, 1)->bRefresh;
        else if (snd_usb_get_speed(chip->dev) == USB_SPEED_FULL)
            ep->syncinterval = 1;
        else if (get_endpoint(alts, 1)->bInterval >= 1 &&
             get_endpoint(alts, 1)->bInterval <= 16)
            ep->syncinterval = get_endpoint(alts, 1)->bInterval - 1;
        else
            ep->syncinterval = 3;

        ep->syncmaxsize = le16_to_cpu(get_endpoint(alts, 1)->wMaxPacketSize);
    }

    list_add_tail(&ep->list, &chip->ep_list);

__exit_unlock:
    mutex_unlock(&chip->mutex);

    return ep;
}

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

    do {
        alive = 0;
        for (i = 0; i < ep->nurbs; i++)
            if (test_bit(i, &ep->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 on EP #%x\n",
                    alive, ep->ep_num);
    clear_bit(EP_FLAG_STOPPING, &ep->flags);

    return 0;
}

/* sync the pending stop operation;
 * this function itself doesn't trigger the stop operation
 */
void snd_usb_endpoint_sync_pending_stop(struct snd_usb_endpoint *ep)
{
    if (ep && test_bit(EP_FLAG_STOPPING, &ep->flags))
        wait_clear_urbs(ep);
}

/*
 * unlink active urbs.
 */
static int deactivate_urbs(struct snd_usb_endpoint *ep, int force, int can_sleep)
{
    unsigned int i;
    int async;

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

    async = !can_sleep && ep->chip->async_unlink;

    clear_bit(EP_FLAG_RUNNING, &ep->flags);

    INIT_LIST_HEAD(&ep->ready_playback_urbs);
    ep->next_packet_read_pos = 0;
    ep->next_packet_write_pos = 0;

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

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

    return 0;
}

/*
 * release an endpoint's urbs
 */
static void release_urbs(struct snd_usb_endpoint *ep, int force)
{
    int i;

    /* route incoming urbs to nirvana */
    ep->retire_data_urb = NULL;
    ep->prepare_data_urb = NULL;

    /* stop urbs */
    deactivate_urbs(ep, force, 1);
    wait_clear_urbs(ep);

    for (i = 0; i < ep->nurbs; i++)
        release_urb_ctx(&ep->urb[i]);

    if (ep->syncbuf)
        usb_free_coherent(ep->chip->dev, SYNC_URBS * 4,
                  ep->syncbuf, ep->sync_dma);

    ep->syncbuf = NULL;
    ep->nurbs = 0;
}

/*
 * configure a data endpoint
 */
static int data_ep_set_params(struct snd_usb_endpoint *ep,
                  snd_pcm_format_t pcm_format,
                  unsigned int channels,
                  unsigned int period_bytes,
                  struct audioformat *fmt,
                  struct snd_usb_endpoint *sync_ep)
{
    unsigned int maxsize, i, urb_packs, total_packs, packs_per_ms;
    int is_playback = usb_pipeout(ep->pipe);
    int frame_bits = snd_pcm_format_physical_width(pcm_format) * channels;

    ep->datainterval = fmt->datainterval;
    ep->stride = frame_bits >> 3;
    ep->silence_value = pcm_format == SNDRV_PCM_FORMAT_U8 ? 0x80 : 0;

    /* calculate max. frequency */
    if (ep->maxpacksize) {
        /* whatever fits into a max. size packet */
        maxsize = ep->maxpacksize;
        ep->freqmax = (maxsize / (frame_bits >> 3))
                << (16 - ep->datainterval);
    } else {
        /* no max. packet size: just take 25% higher than nominal */
        ep->freqmax = ep->freqn + (ep->freqn >> 2);
        maxsize = ((ep->freqmax + 0xffff) * (frame_bits >> 3))
                >> (16 - ep->datainterval);
    }

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

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

    if (is_playback && !snd_usb_endpoint_implict_feedback_sink(ep)) {
        urb_packs = max(ep->chip->nrpacks, 1);
        urb_packs = min(urb_packs, (unsigned int) MAX_PACKS);
    } else {
        urb_packs = 1;
    }

    urb_packs *= packs_per_ms;

    if (sync_ep && !snd_usb_endpoint_implict_feedback_sink(ep))
        urb_packs = min(urb_packs, 1U << sync_ep->syncinterval);

    /* decide how many packets to be used */
    if (is_playback && !snd_usb_endpoint_implict_feedback_sink(ep)) {
        unsigned int minsize, maxpacks;
        /* determine how small a packet can be */
        minsize = (ep->freqn >> (16 - ep->datainterval))
              * (frame_bits >> 3);
        /* with sync from device, assume it can be 12% lower */
        if (sync_ep)
            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;
    }

    ep->nurbs = (total_packs + urb_packs - 1) / urb_packs;
    if (ep->nurbs > MAX_URBS) {
        /* too much... */
        ep->nurbs = MAX_URBS;
        total_packs = MAX_URBS * urb_packs;
    } else if (ep->nurbs < 2) {
        /* too little - we need at least two packets
         * to ensure contiguous playback/capture
         */
        ep->nurbs = 2;
    }

    /* allocate and initialize data urbs */
    for (i = 0; i < ep->nurbs; i++) {
        struct snd_urb_ctx *u = &ep->urb[i];
        u->index = i;
        u->ep = ep;
        u->packets = (i + 1) * total_packs / ep->nurbs
            - i * total_packs / ep->nurbs;
        u->buffer_size = maxsize * u->packets;

        if (fmt->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(ep->chip->dev, u->buffer_size,
                       GFP_KERNEL, &u->urb->transfer_dma);
        if (!u->urb->transfer_buffer)
            goto out_of_memory;
        u->urb->pipe = ep->pipe;
        u->urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;
        u->urb->interval = 1 << ep->datainterval;
        u->urb->context = u;
        u->urb->complete = snd_complete_urb;
        INIT_LIST_HEAD(&u->ready_list);
    }

    return 0;

out_of_memory:
    release_urbs(ep, 0);
    return -ENOMEM;
}

/*
 * configure a sync endpoint
 */
static int sync_ep_set_params(struct snd_usb_endpoint *ep,
                  struct audioformat *fmt)
{
    int i;

    ep->syncbuf = usb_alloc_coherent(ep->chip->dev, SYNC_URBS * 4,
                     GFP_KERNEL, &ep->sync_dma);
    if (!ep->syncbuf)
        return -ENOMEM;

    for (i = 0; i < SYNC_URBS; i++) {
        struct snd_urb_ctx *u = &ep->urb[i];
        u->index = i;
        u->ep = ep;
        u->packets = 1;
        u->urb = usb_alloc_urb(1, GFP_KERNEL);
        if (!u->urb)
            goto out_of_memory;
        u->urb->transfer_buffer = ep->syncbuf + i * 4;
        u->urb->transfer_dma = ep->sync_dma + i * 4;
        u->urb->transfer_buffer_length = 4;
        u->urb->pipe = ep->pipe;
        u->urb->transfer_flags = URB_ISO_ASAP |
                     URB_NO_TRANSFER_DMA_MAP;
        u->urb->number_of_packets = 1;
        u->urb->interval = 1 << ep->syncinterval;
        u->urb->context = u;
        u->urb->complete = snd_complete_urb;
    }

    ep->nurbs = SYNC_URBS;

    return 0;

out_of_memory:
    release_urbs(ep, 0);
    return -ENOMEM;
}

int snd_usb_endpoint_set_params(struct snd_usb_endpoint *ep,
                snd_pcm_format_t pcm_format,
                unsigned int channels,
                unsigned int period_bytes,
                unsigned int rate,
                struct audioformat *fmt,
                struct snd_usb_endpoint *sync_ep)
{
    int err;

    if (ep->use_count != 0) {
        snd_printk(KERN_WARNING "Unable to change format on ep #%x: already in use\n",
               ep->ep_num);
        return -EBUSY;
    }

    /* release old buffers, if any */
    release_urbs(ep, 0);

    ep->datainterval = fmt->datainterval;
    ep->maxpacksize = fmt->maxpacksize;
    ep->fill_max = !!(fmt->attributes & UAC_EP_CS_ATTR_FILL_MAX);

    if (snd_usb_get_speed(ep->chip->dev) == USB_SPEED_FULL)
        ep->freqn = get_usb_full_speed_rate(rate);
    else
        ep->freqn = get_usb_high_speed_rate(rate);

    /* calculate the frequency in 16.16 format */
    ep->freqm = ep->freqn;
    ep->freqshift = INT_MIN;

    ep->phase = 0;

    switch (ep->type) {
    case  SND_USB_ENDPOINT_TYPE_DATA:
        err = data_ep_set_params(ep, pcm_format, channels,
                     period_bytes, fmt, sync_ep);
        break;
    case  SND_USB_ENDPOINT_TYPE_SYNC:
        err = sync_ep_set_params(ep, fmt);
        break;
    default:
        err = -EINVAL;
    }

    snd_printdd(KERN_DEBUG "Setting params for ep #%x (type %d, %d urbs), ret=%d\n",
           ep->ep_num, ep->type, ep->nurbs, err);

    return err;
}

int snd_usb_endpoint_start(struct snd_usb_endpoint *ep, int can_sleep)
{
    int err;
    unsigned int i;

    if (ep->chip->shutdown)
        return -EBADFD;

    /* already running? */
    if (++ep->use_count != 1)
        return 0;

    /* just to be sure */
    deactivate_urbs(ep, 0, can_sleep);
    if (can_sleep)
        wait_clear_urbs(ep);

    ep->active_mask = 0;
    ep->unlink_mask = 0;
    ep->phase = 0;

    snd_usb_endpoint_start_quirk(ep);

    /*
     * If this endpoint has a data endpoint as implicit feedback source,
     * don't start the urbs here. Instead, mark them all as available,
     * wait for the record urbs to return and queue the playback urbs
     * from that context.
     */

    set_bit(EP_FLAG_RUNNING, &ep->flags);

    if (snd_usb_endpoint_implict_feedback_sink(ep)) {
        for (i = 0; i < ep->nurbs; i++) {
            struct snd_urb_ctx *ctx = ep->urb + i;
            list_add_tail(&ctx->ready_list, &ep->ready_playback_urbs);
        }

        return 0;
    }

    for (i = 0; i < ep->nurbs; i++) {
        struct urb *urb = ep->urb[i].urb;

        if (snd_BUG_ON(!urb))
            goto __error;

        if (usb_pipeout(ep->pipe)) {
            prepare_outbound_urb(ep, urb->context);
        } else {
            prepare_inbound_urb(ep, urb->context);
        }

        err = usb_submit_urb(urb, GFP_ATOMIC);
        if (err < 0) {
            snd_printk(KERN_ERR "cannot submit urb %d, error %d: %s\n",
                   i, err, usb_error_string(err));
            goto __error;
        }
        set_bit(i, &ep->active_mask);
    }

    return 0;

__error:
    clear_bit(EP_FLAG_RUNNING, &ep->flags);
    ep->use_count--;
    deactivate_urbs(ep, 0, 0);
    return -EPIPE;
}

void snd_usb_endpoint_stop(struct snd_usb_endpoint *ep,
               int force, int can_sleep, int wait)
{
    if (!ep)
        return;

    if (snd_BUG_ON(ep->use_count == 0))
        return;

    if (--ep->use_count == 0) {
        deactivate_urbs(ep, force, can_sleep);
        ep->data_subs = NULL;
        ep->sync_slave = NULL;
        ep->retire_data_urb = NULL;
        ep->prepare_data_urb = NULL;

        if (wait)
            wait_clear_urbs(ep);
        else
            set_bit(EP_FLAG_STOPPING, &ep->flags);
    }
}

int snd_usb_endpoint_deactivate(struct snd_usb_endpoint *ep)
{
    if (!ep)
        return -EINVAL;

    deactivate_urbs(ep, 1, 1);
    wait_clear_urbs(ep);

    if (ep->use_count != 0)
        return 0;

    clear_bit(EP_FLAG_ACTIVATED, &ep->flags);

    return 0;
}

void snd_usb_endpoint_free(struct list_head *head)
{
    struct snd_usb_endpoint *ep;

    ep = list_entry(head, struct snd_usb_endpoint, list);
    release_urbs(ep, 1);
    kfree(ep);
}

void snd_usb_handle_sync_urb(struct snd_usb_endpoint *ep,
                 struct snd_usb_endpoint *sender,
                 const struct urb *urb)
{
    int shift;
    unsigned int f;
    unsigned long flags;

    snd_BUG_ON(ep == sender);

    /*
     * In case the endpoint is operating in implicit feedback mode, prepare
     * a new outbound URB that has the same layout as the received packet
     * and add it to the list of pending urbs. queue_pending_output_urbs()
     * will take care of them later.
     */
    if (snd_usb_endpoint_implict_feedback_sink(ep) &&
        ep->use_count != 0) {

        /* implicit feedback case */
        int i, bytes = 0;
        struct snd_urb_ctx *in_ctx;
        struct snd_usb_packet_info *out_packet;

        in_ctx = urb->context;

        /* Count overall packet size */
        for (i = 0; i < in_ctx->packets; i++)
            if (urb->iso_frame_desc[i].status == 0)
                bytes += urb->iso_frame_desc[i].actual_length;

        /*
         * skip empty packets. At least M-Audio's Fast Track Ultra stops
         * streaming once it received a 0-byte OUT URB
         */
        if (bytes == 0)
            return;

        spin_lock_irqsave(&ep->lock, flags);
        out_packet = ep->next_packet + ep->next_packet_write_pos;

        /*
         * Iterate through the inbound packet and prepare the lengths
         * for the output packet. The OUT packet we are about to send
         * will have the same amount of payload bytes than the IN
         * packet we just received.
         */

        out_packet->packets = in_ctx->packets;
        for (i = 0; i < in_ctx->packets; i++) {
            if (urb->iso_frame_desc[i].status == 0)
                out_packet->packet_size[i] =
                    urb->iso_frame_desc[i].actual_length / ep->stride;
            else
                out_packet->packet_size[i] = 0;
        }

        ep->next_packet_write_pos++;
        ep->next_packet_write_pos %= MAX_URBS;
        spin_unlock_irqrestore(&ep->lock, flags);
        queue_pending_output_urbs(ep);

        return;
    }

    /*
     * 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.
     */

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

    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;

    if (unlikely(ep->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 < ep->freqn - ep->freqn / 4) {
            f <<= 1;
            shift++;
        }
        while (f > ep->freqn + ep->freqn / 2) {
            f >>= 1;
            shift--;
        }
        ep->freqshift = shift;
    } else if (ep->freqshift >= 0)
        f <<= ep->freqshift;
    else
        f >>= -ep->freqshift;

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