// SPDX-License-Identifier: GPL-2.0-only
/*
 * Edirol UA-101/UA-1000 driver
 * Copyright (c) Clemens Ladisch <clemens@ladisch.de>
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/usb.h>
#include <linux/usb/audio.h>
#include <sound/core.h>
#include <sound/initval.h>
#include <sound/pcm.h>
#include <sound/pcm_params.h>
#include "../usbaudio.h"
#include "../midi.h"

MODULE_DESCRIPTION("Edirol UA-101/1000 driver");
MODULE_AUTHOR("Clemens Ladisch <clemens@ladisch.de>");
MODULE_LICENSE("GPL v2");

/*
 * Should not be lower than the minimum scheduling delay of the host
 * controller.  Some Intel controllers need more than one frame; as long as
 * that driver doesn't tell us about this, use 1.5 frames just to be sure.
 */
#define MIN_QUEUE_LENGTH        12
/* Somewhat random. */
#define MAX_QUEUE_LENGTH        30
/*
 * This magic value optimizes memory usage efficiency for the UA-101's packet
 * sizes at all sample rates, taking into account the stupid cache pool sizes
 * that usb_alloc_coherent() uses.
 */
#define DEFAULT_QUEUE_LENGTH    21

#define MAX_PACKET_SIZE         672 /* hardware specific */
#define MAX_MEMORY_BUFFERS      DIV_ROUND_UP(MAX_QUEUE_LENGTH, \
                                             PAGE_SIZE / MAX_PACKET_SIZE)

static int index[SNDRV_CARDS] = SNDRV_DEFAULT_IDX;
static char *id[SNDRV_CARDS] = SNDRV_DEFAULT_STR;
static bool enable[SNDRV_CARDS] = SNDRV_DEFAULT_ENABLE_PNP;
static unsigned int queue_length = 21;

module_param_array(index, int, NULL, 0444);
MODULE_PARM_DESC(index, "card index");
module_param_array(id, charp, NULL, 0444);
MODULE_PARM_DESC(id, "ID string");
module_param_array(enable, bool, NULL, 0444);
MODULE_PARM_DESC(enable, "enable card");
module_param(queue_length, uint, 0644);
MODULE_PARM_DESC(queue_length, "USB queue length in microframes, "
                 __stringify(MIN_QUEUE_LENGTH)"-"__stringify(MAX_QUEUE_LENGTH));

enum {
        INTF_PLAYBACK,
        INTF_CAPTURE,
        INTF_MIDI,

        INTF_COUNT
};

/* bits in struct ua101::states */
enum {
        USB_CAPTURE_RUNNING,
        USB_PLAYBACK_RUNNING,
        ALSA_CAPTURE_OPEN,
        ALSA_PLAYBACK_OPEN,
        ALSA_CAPTURE_RUNNING,
        ALSA_PLAYBACK_RUNNING,
        CAPTURE_URB_COMPLETED,
        PLAYBACK_URB_COMPLETED,
        DISCONNECTED,
};

struct ua101 {
        struct usb_device *dev;
        struct snd_card *card;
        struct usb_interface *intf[INTF_COUNT];
        int card_index;
        struct snd_pcm *pcm;
        struct list_head midi_list;
        u64 format_bit;
        unsigned int rate;
        unsigned int packets_per_second;
        spinlock_t lock;
        struct mutex mutex;
        unsigned long states;

        /* FIFO to synchronize playback rate to capture rate */
        unsigned int rate_feedback_start;
        unsigned int rate_feedback_count;
        u8 rate_feedback[MAX_QUEUE_LENGTH];

        struct list_head ready_playback_urbs;
        struct work_struct playback_work;
        wait_queue_head_t alsa_capture_wait;
        wait_queue_head_t rate_feedback_wait;
        wait_queue_head_t alsa_playback_wait;
        struct ua101_stream {
                struct snd_pcm_substream *substream;
                unsigned int usb_pipe;
                unsigned int channels;
                unsigned int frame_bytes;
                unsigned int max_packet_bytes;
                unsigned int period_pos;
                unsigned int buffer_pos;
                unsigned int queue_length;
                struct ua101_urb {
                        struct urb urb;
                        struct usb_iso_packet_descriptor iso_frame_desc[1];
                        struct list_head ready_list;
                } *urbs[MAX_QUEUE_LENGTH];
                struct {
                        unsigned int size;
                        void *addr;
                        dma_addr_t dma;
                } buffers[MAX_MEMORY_BUFFERS];
        } capture, playback;
};

static DEFINE_MUTEX(devices_mutex);
static unsigned int devices_used;
static struct usb_driver ua101_driver;

static void abort_alsa_playback(struct ua101 *ua);
static void abort_alsa_capture(struct ua101 *ua);

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";
        }
}

static void abort_usb_capture(struct ua101 *ua)
{
        if (test_and_clear_bit(USB_CAPTURE_RUNNING, &ua->states)) {
                wake_up(&ua->alsa_capture_wait);
                wake_up(&ua->rate_feedback_wait);
        }
}

static void abort_usb_playback(struct ua101 *ua)
{
        if (test_and_clear_bit(USB_PLAYBACK_RUNNING, &ua->states))
                wake_up(&ua->alsa_playback_wait);
}

static void playback_urb_complete(struct urb *usb_urb)
{
        struct ua101_urb *urb = (struct ua101_urb *)usb_urb;
        struct ua101 *ua = urb->urb.context;

        if (unlikely(urb->urb.status == -ENOENT ||      /* unlinked */
                     urb->urb.status == -ENODEV ||      /* device removed */
                     urb->urb.status == -ECONNRESET ||  /* unlinked */
                     urb->urb.status == -ESHUTDOWN)) {  /* device disabled */
                abort_usb_playback(ua);
                abort_alsa_playback(ua);
                return;
        }

        if (test_bit(USB_PLAYBACK_RUNNING, &ua->states)) {
                /* append URB to FIFO */
                guard(spinlock_irqsave)(&ua->lock);
                list_add_tail(&urb->ready_list, &ua->ready_playback_urbs);
                if (ua->rate_feedback_count > 0)
                        queue_work(system_highpri_wq, &ua->playback_work);
                ua->playback.substream->runtime->delay -=
                                urb->urb.iso_frame_desc[0].length /
                                                ua->playback.frame_bytes;
        }
}

static void first_playback_urb_complete(struct urb *urb)
{
        struct ua101 *ua = urb->context;

        urb->complete = playback_urb_complete;
        playback_urb_complete(urb);

        set_bit(PLAYBACK_URB_COMPLETED, &ua->states);
        wake_up(&ua->alsa_playback_wait);
}

/* copy data from the ALSA ring buffer into the URB buffer */
static bool copy_playback_data(struct ua101_stream *stream, struct urb *urb,
                               unsigned int frames)
{
        struct snd_pcm_runtime *runtime;
        unsigned int frame_bytes, frames1;
        const u8 *source;

        runtime = stream->substream->runtime;
        frame_bytes = stream->frame_bytes;
        source = runtime->dma_area + stream->buffer_pos * frame_bytes;
        if (stream->buffer_pos + frames <= runtime->buffer_size) {
                memcpy(urb->transfer_buffer, source, frames * frame_bytes);
        } else {
                /* wrap around at end of ring buffer */
                frames1 = runtime->buffer_size - stream->buffer_pos;
                memcpy(urb->transfer_buffer, source, frames1 * frame_bytes);
                memcpy(urb->transfer_buffer + frames1 * frame_bytes,
                       runtime->dma_area, (frames - frames1) * frame_bytes);
        }

        stream->buffer_pos += frames;
        if (stream->buffer_pos >= runtime->buffer_size)
                stream->buffer_pos -= runtime->buffer_size;
        stream->period_pos += frames;
        if (stream->period_pos >= runtime->period_size) {
                stream->period_pos -= runtime->period_size;
                return true;
        }
        return false;
}

static inline void add_with_wraparound(struct ua101 *ua,
                                       unsigned int *value, unsigned int add)
{
        *value += add;
        if (*value >= ua->playback.queue_length)
                *value -= ua->playback.queue_length;
}

static void playback_work(struct work_struct *work)
{
        struct ua101 *ua = container_of(work, struct ua101, playback_work);
        unsigned int frames;
        struct ua101_urb *urb;
        bool do_period_elapsed = false;
        int err;

        if (unlikely(!test_bit(USB_PLAYBACK_RUNNING, &ua->states)))
                return;

        /*
         * Synchronizing the playback rate to the capture rate is done by using
         * the same sequence of packet sizes for both streams.
         * Submitting a playback URB therefore requires both a ready URB and
         * the size of the corresponding capture packet, i.e., both playback
         * and capture URBs must have been completed.  Since the USB core does
         * not guarantee that playback and capture complete callbacks are
         * called alternately, we use two FIFOs for packet sizes and read URBs;
         * submitting playback URBs is possible as long as both FIFOs are
         * nonempty.
         */
        scoped_guard(spinlock_irqsave, &ua->lock) {
                while (ua->rate_feedback_count > 0 &&
                       !list_empty(&ua->ready_playback_urbs)) {
                        /* take packet size out of FIFO */
                        frames = ua->rate_feedback[ua->rate_feedback_start];
                        add_with_wraparound(ua, &ua->rate_feedback_start, 1);
                        ua->rate_feedback_count--;

                        /* take URB out of FIFO */
                        urb = list_first_entry(&ua->ready_playback_urbs,
                                               struct ua101_urb, ready_list);
                        list_del(&urb->ready_list);

                        /* fill packet with data or silence */
                        urb->urb.iso_frame_desc[0].length =
                                frames * ua->playback.frame_bytes;
                        if (test_bit(ALSA_PLAYBACK_RUNNING, &ua->states))
                                do_period_elapsed |= copy_playback_data(&ua->playback,
                                                                        &urb->urb,
                                                                        frames);
                        else
                                memset(urb->urb.transfer_buffer, 0,
                                       urb->urb.iso_frame_desc[0].length);

                        /* and off you go ... */
                        err = usb_submit_urb(&urb->urb, GFP_ATOMIC);
                        if (unlikely(err < 0)) {
                                abort_usb_playback(ua);
                                abort_alsa_playback(ua);
                                dev_err(&ua->dev->dev, "USB request error %d: %s\n",
                                        err, usb_error_string(err));
                                return;
                        }
                        ua->playback.substream->runtime->delay += frames;
                }
        }

        if (do_period_elapsed)
                snd_pcm_period_elapsed(ua->playback.substream);
}

/* copy data from the URB buffer into the ALSA ring buffer */
static bool copy_capture_data(struct ua101_stream *stream, struct urb *urb,
                              unsigned int frames)
{
        struct snd_pcm_runtime *runtime;
        unsigned int frame_bytes, frames1;
        u8 *dest;

        runtime = stream->substream->runtime;
        frame_bytes = stream->frame_bytes;
        dest = runtime->dma_area + stream->buffer_pos * frame_bytes;
        if (stream->buffer_pos + frames <= runtime->buffer_size) {
                memcpy(dest, urb->transfer_buffer, frames * frame_bytes);
        } else {
                /* wrap around at end of ring buffer */
                frames1 = runtime->buffer_size - stream->buffer_pos;
                memcpy(dest, urb->transfer_buffer, frames1 * frame_bytes);
                memcpy(runtime->dma_area,
                       urb->transfer_buffer + frames1 * frame_bytes,
                       (frames - frames1) * frame_bytes);
        }

        stream->buffer_pos += frames;
        if (stream->buffer_pos >= runtime->buffer_size)
                stream->buffer_pos -= runtime->buffer_size;
        stream->period_pos += frames;
        if (stream->period_pos >= runtime->period_size) {
                stream->period_pos -= runtime->period_size;
                return true;
        }
        return false;
}

static void capture_urb_complete(struct urb *urb)
{
        struct ua101 *ua = urb->context;
        struct ua101_stream *stream = &ua->capture;
        unsigned int frames, write_ptr;
        bool do_period_elapsed;
        int err;

        if (unlikely(urb->status == -ENOENT ||          /* unlinked */
                     urb->status == -ENODEV ||          /* device removed */
                     urb->status == -ECONNRESET ||      /* unlinked */
                     urb->status == -ESHUTDOWN))        /* device disabled */
                goto stream_stopped;

        if (urb->status >= 0 && urb->iso_frame_desc[0].status >= 0)
                frames = urb->iso_frame_desc[0].actual_length /
                        stream->frame_bytes;
        else
                frames = 0;

        scoped_guard(spinlock_irqsave, &ua->lock) {

                if (frames > 0 && test_bit(ALSA_CAPTURE_RUNNING, &ua->states))
                        do_period_elapsed = copy_capture_data(stream, urb, frames);
                else
                        do_period_elapsed = false;

                if (test_bit(USB_CAPTURE_RUNNING, &ua->states)) {
                        err = usb_submit_urb(urb, GFP_ATOMIC);
                        if (unlikely(err < 0)) {
                                dev_err(&ua->dev->dev, "USB request error %d: %s\n",
                                        err, usb_error_string(err));
                                goto stream_stopped;
                        }

                        /* append packet size to FIFO */
                        write_ptr = ua->rate_feedback_start;
                        add_with_wraparound(ua, &write_ptr, ua->rate_feedback_count);
                        ua->rate_feedback[write_ptr] = frames;
                        if (ua->rate_feedback_count < ua->playback.queue_length) {
                                ua->rate_feedback_count++;
                                if (ua->rate_feedback_count ==
                                    ua->playback.queue_length)
                                        wake_up(&ua->rate_feedback_wait);
                        } else {
                                /*
                                 * Ring buffer overflow; this happens when the playback
                                 * stream is not running.  Throw away the oldest entry,
                                 * so that the playback stream, when it starts, sees
                                 * the most recent packet sizes.
                                 */
                                add_with_wraparound(ua, &ua->rate_feedback_start, 1);
                        }
                        if (test_bit(USB_PLAYBACK_RUNNING, &ua->states) &&
                            !list_empty(&ua->ready_playback_urbs))
                                queue_work(system_highpri_wq, &ua->playback_work);
                }
        }

        if (do_period_elapsed)
                snd_pcm_period_elapsed(stream->substream);

        return;

stream_stopped:
        abort_usb_playback(ua);
        abort_usb_capture(ua);
        abort_alsa_playback(ua);
        abort_alsa_capture(ua);
}

static void first_capture_urb_complete(struct urb *urb)
{
        struct ua101 *ua = urb->context;

        urb->complete = capture_urb_complete;
        capture_urb_complete(urb);

        set_bit(CAPTURE_URB_COMPLETED, &ua->states);
        wake_up(&ua->alsa_capture_wait);
}

static int submit_stream_urbs(struct ua101 *ua, struct ua101_stream *stream)
{
        unsigned int i;

        for (i = 0; i < stream->queue_length; ++i) {
                int err = usb_submit_urb(&stream->urbs[i]->urb, GFP_KERNEL);
                if (err < 0) {
                        dev_err(&ua->dev->dev, "USB request error %d: %s\n",
                                err, usb_error_string(err));
                        return err;
                }
        }
        return 0;
}

static void kill_stream_urbs(struct ua101_stream *stream)
{
        unsigned int i;

        for (i = 0; i < stream->queue_length; ++i)
                if (stream->urbs[i])
                        usb_kill_urb(&stream->urbs[i]->urb);
}

static int enable_iso_interface(struct ua101 *ua, unsigned int intf_index)
{
        struct usb_host_interface *alts;

        alts = ua->intf[intf_index]->cur_altsetting;
        if (alts->desc.bAlternateSetting != 1) {
                int err = usb_set_interface(ua->dev,
                                            alts->desc.bInterfaceNumber, 1);
                if (err < 0) {
                        dev_err(&ua->dev->dev,
                                "cannot initialize interface; error %d: %s\n",
                                err, usb_error_string(err));
                        return err;
                }
        }
        return 0;
}

static void disable_iso_interface(struct ua101 *ua, unsigned int intf_index)
{
        struct usb_host_interface *alts;

        if (!ua->intf[intf_index])
                return;

        alts = ua->intf[intf_index]->cur_altsetting;
        if (alts->desc.bAlternateSetting != 0) {
                int err = usb_set_interface(ua->dev,
                                            alts->desc.bInterfaceNumber, 0);
                if (err < 0 && !test_bit(DISCONNECTED, &ua->states))
                        dev_warn(&ua->dev->dev,
                                 "interface reset failed; error %d: %s\n",
                                 err, usb_error_string(err));
        }
}

static void stop_usb_capture(struct ua101 *ua)
{
        clear_bit(USB_CAPTURE_RUNNING, &ua->states);

        kill_stream_urbs(&ua->capture);

        disable_iso_interface(ua, INTF_CAPTURE);
}

static int start_usb_capture(struct ua101 *ua)
{
        int err;

        if (test_bit(DISCONNECTED, &ua->states))
                return -ENODEV;

        if (test_bit(USB_CAPTURE_RUNNING, &ua->states))
                return 0;

        kill_stream_urbs(&ua->capture);

        err = enable_iso_interface(ua, INTF_CAPTURE);
        if (err < 0)
                return err;

        clear_bit(CAPTURE_URB_COMPLETED, &ua->states);
        ua->capture.urbs[0]->urb.complete = first_capture_urb_complete;
        ua->rate_feedback_start = 0;
        ua->rate_feedback_count = 0;

        set_bit(USB_CAPTURE_RUNNING, &ua->states);
        err = submit_stream_urbs(ua, &ua->capture);
        if (err < 0)
                stop_usb_capture(ua);
        return err;
}

static void stop_usb_playback(struct ua101 *ua)
{
        clear_bit(USB_PLAYBACK_RUNNING, &ua->states);

        kill_stream_urbs(&ua->playback);

        cancel_work_sync(&ua->playback_work);

        disable_iso_interface(ua, INTF_PLAYBACK);
}

static int start_usb_playback(struct ua101 *ua)
{
        unsigned int i, frames;
        struct urb *urb;
        int err = 0;

        if (test_bit(DISCONNECTED, &ua->states))
                return -ENODEV;

        if (test_bit(USB_PLAYBACK_RUNNING, &ua->states))
                return 0;

        kill_stream_urbs(&ua->playback);
        cancel_work_sync(&ua->playback_work);

        err = enable_iso_interface(ua, INTF_PLAYBACK);
        if (err < 0)
                return err;

        clear_bit(PLAYBACK_URB_COMPLETED, &ua->states);
        ua->playback.urbs[0]->urb.complete =
                first_playback_urb_complete;
        scoped_guard(spinlock_irq, &ua->lock) {
                INIT_LIST_HEAD(&ua->ready_playback_urbs);
        }

        /*
         * We submit the initial URBs all at once, so we have to wait for the
         * packet size FIFO to be full.
         */
        wait_event(ua->rate_feedback_wait,
                   ua->rate_feedback_count >= ua->playback.queue_length ||
                   !test_bit(USB_CAPTURE_RUNNING, &ua->states) ||
                   test_bit(DISCONNECTED, &ua->states));
        if (test_bit(DISCONNECTED, &ua->states)) {
                stop_usb_playback(ua);
                return -ENODEV;
        }
        if (!test_bit(USB_CAPTURE_RUNNING, &ua->states)) {
                stop_usb_playback(ua);
                return -EIO;
        }

        for (i = 0; i < ua->playback.queue_length; ++i) {
                /* all initial URBs contain silence */
                scoped_guard(spinlock_irq, &ua->lock) {
                        frames = ua->rate_feedback[ua->rate_feedback_start];
                        add_with_wraparound(ua, &ua->rate_feedback_start, 1);
                        ua->rate_feedback_count--;
                }
                urb = &ua->playback.urbs[i]->urb;
                urb->iso_frame_desc[0].length =
                        frames * ua->playback.frame_bytes;
                memset(urb->transfer_buffer, 0,
                       urb->iso_frame_desc[0].length);
        }

        set_bit(USB_PLAYBACK_RUNNING, &ua->states);
        err = submit_stream_urbs(ua, &ua->playback);
        if (err < 0)
                stop_usb_playback(ua);
        return err;
}

static void abort_alsa_capture(struct ua101 *ua)
{
        if (test_bit(ALSA_CAPTURE_RUNNING, &ua->states))
                snd_pcm_stop_xrun(ua->capture.substream);
}

static void abort_alsa_playback(struct ua101 *ua)
{
        if (test_bit(ALSA_PLAYBACK_RUNNING, &ua->states))
                snd_pcm_stop_xrun(ua->playback.substream);
}

static int set_stream_hw(struct ua101 *ua, struct snd_pcm_substream *substream,
                         unsigned int channels)
{
        int err;

        substream->runtime->hw.info =
                SNDRV_PCM_INFO_MMAP |
                SNDRV_PCM_INFO_MMAP_VALID |
                SNDRV_PCM_INFO_BATCH |
                SNDRV_PCM_INFO_INTERLEAVED |
                SNDRV_PCM_INFO_BLOCK_TRANSFER |
                SNDRV_PCM_INFO_FIFO_IN_FRAMES;
        substream->runtime->hw.formats = ua->format_bit;
        substream->runtime->hw.rates = snd_pcm_rate_to_rate_bit(ua->rate);
        substream->runtime->hw.rate_min = ua->rate;
        substream->runtime->hw.rate_max = ua->rate;
        substream->runtime->hw.channels_min = channels;
        substream->runtime->hw.channels_max = channels;
        substream->runtime->hw.buffer_bytes_max = 45000 * 1024;
        substream->runtime->hw.period_bytes_min = 1;
        substream->runtime->hw.period_bytes_max = UINT_MAX;
        substream->runtime->hw.periods_min = 2;
        substream->runtime->hw.periods_max = UINT_MAX;
        err = snd_pcm_hw_constraint_minmax(substream->runtime,
                                           SNDRV_PCM_HW_PARAM_PERIOD_TIME,
                                           1500000 / ua->packets_per_second,
                                           UINT_MAX);
        if (err < 0)
                return err;
        err = snd_pcm_hw_constraint_msbits(substream->runtime, 0, 32, 24);
        return err;
}

static int capture_pcm_open(struct snd_pcm_substream *substream)
{
        struct ua101 *ua = substream->private_data;
        int err;

        ua->capture.substream = substream;
        err = set_stream_hw(ua, substream, ua->capture.channels);
        if (err < 0)
                return err;
        substream->runtime->hw.fifo_size =
                DIV_ROUND_CLOSEST(ua->rate, ua->packets_per_second);
        substream->runtime->delay = substream->runtime->hw.fifo_size;

        guard(mutex)(&ua->mutex);
        err = start_usb_capture(ua);
        if (err >= 0)
                set_bit(ALSA_CAPTURE_OPEN, &ua->states);
        return err;
}

static int playback_pcm_open(struct snd_pcm_substream *substream)
{
        struct ua101 *ua = substream->private_data;
        int err;

        ua->playback.substream = substream;
        err = set_stream_hw(ua, substream, ua->playback.channels);
        if (err < 0)
                return err;
        substream->runtime->hw.fifo_size =
                DIV_ROUND_CLOSEST(ua->rate * ua->playback.queue_length,
                                  ua->packets_per_second);

        guard(mutex)(&ua->mutex);
        err = start_usb_capture(ua);
        if (err < 0)
                return err;
        err = start_usb_playback(ua);
        if (err < 0) {
                if (!test_bit(ALSA_CAPTURE_OPEN, &ua->states))
                        stop_usb_capture(ua);
                return err;
        }
        set_bit(ALSA_PLAYBACK_OPEN, &ua->states);
        return 0;
}

static int capture_pcm_close(struct snd_pcm_substream *substream)
{
        struct ua101 *ua = substream->private_data;

        guard(mutex)(&ua->mutex);
        clear_bit(ALSA_CAPTURE_OPEN, &ua->states);
        if (!test_bit(ALSA_PLAYBACK_OPEN, &ua->states))
                stop_usb_capture(ua);
        return 0;
}

static int playback_pcm_close(struct snd_pcm_substream *substream)
{
        struct ua101 *ua = substream->private_data;

        guard(mutex)(&ua->mutex);
        stop_usb_playback(ua);
        clear_bit(ALSA_PLAYBACK_OPEN, &ua->states);
        if (!test_bit(ALSA_CAPTURE_OPEN, &ua->states))
                stop_usb_capture(ua);
        return 0;
}

static int capture_pcm_hw_params(struct snd_pcm_substream *substream,
                                 struct snd_pcm_hw_params *hw_params)
{
        struct ua101 *ua = substream->private_data;

        guard(mutex)(&ua->mutex);
        return start_usb_capture(ua);
}

static int playback_pcm_hw_params(struct snd_pcm_substream *substream,
                                  struct snd_pcm_hw_params *hw_params)
{
        struct ua101 *ua = substream->private_data;
        int err;

        guard(mutex)(&ua->mutex);
        err = start_usb_capture(ua);
        if (err >= 0)
                err = start_usb_playback(ua);
        return err;
}

static int capture_pcm_prepare(struct snd_pcm_substream *substream)
{
        struct ua101 *ua = substream->private_data;
        int err;

        scoped_guard(mutex, &ua->mutex) {
                err = start_usb_capture(ua);
        }
        if (err < 0)
                return err;

        /*
         * The EHCI driver schedules the first packet of an iso stream at 10 ms
         * in the future, i.e., no data is actually captured for that long.
         * Take the wait here so that the stream is known to be actually
         * running when the start trigger has been called.
         */
        wait_event(ua->alsa_capture_wait,
                   test_bit(CAPTURE_URB_COMPLETED, &ua->states) ||
                   !test_bit(USB_CAPTURE_RUNNING, &ua->states));
        if (test_bit(DISCONNECTED, &ua->states))
                return -ENODEV;
        if (!test_bit(USB_CAPTURE_RUNNING, &ua->states))
                return -EIO;

        ua->capture.period_pos = 0;
        ua->capture.buffer_pos = 0;
        return 0;
}

static int playback_pcm_prepare(struct snd_pcm_substream *substream)
{
        struct ua101 *ua = substream->private_data;
        int err;

        scoped_guard(mutex, &ua->mutex) {
                err = start_usb_capture(ua);
                if (err >= 0)
                        err = start_usb_playback(ua);
        }
        if (err < 0)
                return err;

        /* see the comment in capture_pcm_prepare() */
        wait_event(ua->alsa_playback_wait,
                   test_bit(PLAYBACK_URB_COMPLETED, &ua->states) ||
                   !test_bit(USB_PLAYBACK_RUNNING, &ua->states));
        if (test_bit(DISCONNECTED, &ua->states))
                return -ENODEV;
        if (!test_bit(USB_PLAYBACK_RUNNING, &ua->states))
                return -EIO;

        substream->runtime->delay = 0;
        ua->playback.period_pos = 0;
        ua->playback.buffer_pos = 0;
        return 0;
}

static int capture_pcm_trigger(struct snd_pcm_substream *substream, int cmd)
{
        struct ua101 *ua = substream->private_data;

        switch (cmd) {
        case SNDRV_PCM_TRIGGER_START:
                if (!test_bit(USB_CAPTURE_RUNNING, &ua->states))
                        return -EIO;
                set_bit(ALSA_CAPTURE_RUNNING, &ua->states);
                return 0;
        case SNDRV_PCM_TRIGGER_STOP:
                clear_bit(ALSA_CAPTURE_RUNNING, &ua->states);
                return 0;
        default:
                return -EINVAL;
        }
}

static int playback_pcm_trigger(struct snd_pcm_substream *substream, int cmd)
{
        struct ua101 *ua = substream->private_data;

        switch (cmd) {
        case SNDRV_PCM_TRIGGER_START:
                if (!test_bit(USB_PLAYBACK_RUNNING, &ua->states))
                        return -EIO;
                set_bit(ALSA_PLAYBACK_RUNNING, &ua->states);
                return 0;
        case SNDRV_PCM_TRIGGER_STOP:
                clear_bit(ALSA_PLAYBACK_RUNNING, &ua->states);
                return 0;
        default:
                return -EINVAL;
        }
}

static inline snd_pcm_uframes_t ua101_pcm_pointer(struct ua101 *ua,
                                                  struct ua101_stream *stream)
{
        guard(spinlock_irqsave)(&ua->lock);
        return stream->buffer_pos;
}

static snd_pcm_uframes_t capture_pcm_pointer(struct snd_pcm_substream *subs)
{
        struct ua101 *ua = subs->private_data;

        return ua101_pcm_pointer(ua, &ua->capture);
}

static snd_pcm_uframes_t playback_pcm_pointer(struct snd_pcm_substream *subs)
{
        struct ua101 *ua = subs->private_data;

        return ua101_pcm_pointer(ua, &ua->playback);
}

static const struct snd_pcm_ops capture_pcm_ops = {
        .open = capture_pcm_open,
        .close = capture_pcm_close,
        .hw_params = capture_pcm_hw_params,
        .prepare = capture_pcm_prepare,
        .trigger = capture_pcm_trigger,
        .pointer = capture_pcm_pointer,
};

static const struct snd_pcm_ops playback_pcm_ops = {
        .open = playback_pcm_open,
        .close = playback_pcm_close,
        .hw_params = playback_pcm_hw_params,
        .prepare = playback_pcm_prepare,
        .trigger = playback_pcm_trigger,
        .pointer = playback_pcm_pointer,
};

static const struct uac_format_type_i_discrete_descriptor *
find_format_descriptor(struct usb_interface *interface)
{
        struct usb_host_interface *alt;
        u8 *extra;
        int extralen;

        if (interface->num_altsetting != 2) {
                dev_err(&interface->dev, "invalid num_altsetting\n");
                return NULL;
        }

        alt = &interface->altsetting[0];
        if (alt->desc.bNumEndpoints != 0) {
                dev_err(&interface->dev, "invalid bNumEndpoints\n");
                return NULL;
        }

        alt = &interface->altsetting[1];
        if (alt->desc.bNumEndpoints != 1) {
                dev_err(&interface->dev, "invalid bNumEndpoints\n");
                return NULL;
        }

        extra = alt->extra;
        extralen = alt->extralen;
        while (extralen >= sizeof(struct usb_descriptor_header)) {
                struct uac_format_type_i_discrete_descriptor *desc;

                desc = (struct uac_format_type_i_discrete_descriptor *)extra;
                if (desc->bLength > extralen) {
                        dev_err(&interface->dev, "descriptor overflow\n");
                        return NULL;
                }
                if (desc->bLength == UAC_FORMAT_TYPE_I_DISCRETE_DESC_SIZE(1) &&
                    desc->bDescriptorType == USB_DT_CS_INTERFACE &&
                    desc->bDescriptorSubtype == UAC_FORMAT_TYPE) {
                        if (desc->bFormatType != UAC_FORMAT_TYPE_I_PCM ||
                            desc->bSamFreqType != 1) {
                                dev_err(&interface->dev,
                                        "invalid format type\n");
                                return NULL;
                        }
                        return desc;
                }
                extralen -= desc->bLength;
                extra += desc->bLength;
        }
        dev_err(&interface->dev, "sample format descriptor not found\n");
        return NULL;
}

static int detect_usb_format(struct ua101 *ua)
{
        const struct uac_format_type_i_discrete_descriptor *fmt_capture;
        const struct uac_format_type_i_discrete_descriptor *fmt_playback;
        const struct usb_endpoint_descriptor *epd;
        unsigned int rate2;

        fmt_capture = find_format_descriptor(ua->intf[INTF_CAPTURE]);
        fmt_playback = find_format_descriptor(ua->intf[INTF_PLAYBACK]);
        if (!fmt_capture || !fmt_playback)
                return -ENXIO;

        switch (fmt_capture->bSubframeSize) {
        case 3:
                ua->format_bit = SNDRV_PCM_FMTBIT_S24_3LE;
                break;
        case 4:
                ua->format_bit = SNDRV_PCM_FMTBIT_S32_LE;
                break;
        default:
                dev_err(&ua->dev->dev, "sample width is not 24 or 32 bits\n");
                return -ENXIO;
        }
        if (fmt_capture->bSubframeSize != fmt_playback->bSubframeSize) {
                dev_err(&ua->dev->dev,
                        "playback/capture sample widths do not match\n");
                return -ENXIO;
        }

        if (fmt_capture->bBitResolution != 24 ||
            fmt_playback->bBitResolution != 24) {
                dev_err(&ua->dev->dev, "sample width is not 24 bits\n");
                return -ENXIO;
        }

        ua->rate = combine_triple(fmt_capture->tSamFreq[0]);
        rate2 = combine_triple(fmt_playback->tSamFreq[0]);
        if (ua->rate != rate2) {
                dev_err(&ua->dev->dev,
                        "playback/capture rates do not match: %u/%u\n",
                        rate2, ua->rate);
                return -ENXIO;
        }

        switch (ua->dev->speed) {
        case USB_SPEED_FULL:
                ua->packets_per_second = 1000;
                break;
        case USB_SPEED_HIGH:
                ua->packets_per_second = 8000;
                break;
        default:
                dev_err(&ua->dev->dev, "unknown device speed\n");
                return -ENXIO;
        }

        ua->capture.channels = fmt_capture->bNrChannels;
        ua->playback.channels = fmt_playback->bNrChannels;
        ua->capture.frame_bytes =
                fmt_capture->bSubframeSize * ua->capture.channels;
        ua->playback.frame_bytes =
                fmt_playback->bSubframeSize * ua->playback.channels;

        epd = &ua->intf[INTF_CAPTURE]->altsetting[1].endpoint[0].desc;
        if (!usb_endpoint_is_isoc_in(epd) || usb_endpoint_maxp(epd) == 0) {
                dev_err(&ua->dev->dev, "invalid capture endpoint\n");
                return -ENXIO;
        }
        ua->capture.usb_pipe = usb_rcvisocpipe(ua->dev, usb_endpoint_num(epd));
        ua->capture.max_packet_bytes = usb_endpoint_maxp(epd);

        epd = &ua->intf[INTF_PLAYBACK]->altsetting[1].endpoint[0].desc;
        if (!usb_endpoint_is_isoc_out(epd) || usb_endpoint_maxp(epd) == 0) {
                dev_err(&ua->dev->dev, "invalid playback endpoint\n");
                return -ENXIO;
        }
        ua->playback.usb_pipe = usb_sndisocpipe(ua->dev, usb_endpoint_num(epd));
        ua->playback.max_packet_bytes = usb_endpoint_maxp(epd);
        return 0;
}

static int alloc_stream_buffers(struct ua101 *ua, struct ua101_stream *stream)
{
        unsigned int remaining_packets, packets, packets_per_page, i;
        size_t size;

        stream->queue_length = queue_length;
        stream->queue_length = max(stream->queue_length,
                                   (unsigned int)MIN_QUEUE_LENGTH);
        stream->queue_length = min(stream->queue_length,
                                   (unsigned int)MAX_QUEUE_LENGTH);

        /*
         * The cache pool sizes used by usb_alloc_coherent() (128, 512, 2048) are
         * quite bad when used with the packet sizes of this device (e.g. 280,
         * 520, 624).  Therefore, we allocate and subdivide entire pages, using
         * a smaller buffer only for the last chunk.
         */
        remaining_packets = stream->queue_length;
        packets_per_page = PAGE_SIZE / stream->max_packet_bytes;
        for (i = 0; i < ARRAY_SIZE(stream->buffers); ++i) {
                packets = min(remaining_packets, packets_per_page);
                size = packets * stream->max_packet_bytes;
                stream->buffers[i].addr =
                        usb_alloc_coherent(ua->dev, size, GFP_KERNEL,
                                           &stream->buffers[i].dma);
                if (!stream->buffers[i].addr)
                        return -ENOMEM;
                stream->buffers[i].size = size;
                remaining_packets -= packets;
                if (!remaining_packets)
                        break;
        }
        if (remaining_packets) {
                dev_err(&ua->dev->dev, "too many packets\n");
                return -ENXIO;
        }
        return 0;
}

static void free_stream_buffers(struct ua101 *ua, struct ua101_stream *stream)
{
        unsigned int i;

        for (i = 0; i < ARRAY_SIZE(stream->buffers); ++i)
                usb_free_coherent(ua->dev,
                                  stream->buffers[i].size,
                                  stream->buffers[i].addr,
                                  stream->buffers[i].dma);
}

static int alloc_stream_urbs(struct ua101 *ua, struct ua101_stream *stream,
                             void (*urb_complete)(struct urb *))
{
        unsigned max_packet_size = stream->max_packet_bytes;
        struct ua101_urb *urb;
        unsigned int b, u = 0;

        for (b = 0; b < ARRAY_SIZE(stream->buffers); ++b) {
                unsigned int size = stream->buffers[b].size;
                u8 *addr = stream->buffers[b].addr;
                dma_addr_t dma = stream->buffers[b].dma;

                while (size >= max_packet_size) {
                        if (u >= stream->queue_length)
                                goto bufsize_error;
                        urb = kmalloc_obj(*urb);
                        if (!urb)
                                return -ENOMEM;
                        usb_init_urb(&urb->urb);
                        urb->urb.dev = ua->dev;
                        urb->urb.pipe = stream->usb_pipe;
                        urb->urb.transfer_flags = URB_NO_TRANSFER_DMA_MAP;
                        urb->urb.transfer_buffer = addr;
                        urb->urb.transfer_dma = dma;
                        urb->urb.transfer_buffer_length = max_packet_size;
                        urb->urb.number_of_packets = 1;
                        urb->urb.interval = 1;
                        urb->urb.context = ua;
                        urb->urb.complete = urb_complete;
                        urb->urb.iso_frame_desc[0].offset = 0;
                        urb->urb.iso_frame_desc[0].length = max_packet_size;
                        stream->urbs[u++] = urb;
                        size -= max_packet_size;
                        addr += max_packet_size;
                        dma += max_packet_size;
                }
        }
        if (u == stream->queue_length)
                return 0;
bufsize_error:
        dev_err(&ua->dev->dev, "internal buffer size error\n");
        return -ENXIO;
}

static void free_stream_urbs(struct ua101_stream *stream)
{
        unsigned int i;

        for (i = 0; i < stream->queue_length; ++i) {
                kfree(stream->urbs[i]);
                stream->urbs[i] = NULL;
        }
}

static void free_usb_related_resources(struct ua101 *ua,
                                       struct usb_interface *interface)
{
        unsigned int i;
        struct usb_interface *intf;

        scoped_guard(mutex, &ua->mutex) {
                free_stream_urbs(&ua->capture);
                free_stream_urbs(&ua->playback);
        }
        free_stream_buffers(ua, &ua->capture);
        free_stream_buffers(ua, &ua->playback);

        for (i = 0; i < ARRAY_SIZE(ua->intf); ++i) {
                scoped_guard(mutex, &ua->mutex) {
                        intf = ua->intf[i];
                        ua->intf[i] = NULL;
                }
                if (intf) {
                        usb_set_intfdata(intf, NULL);
                        if (intf != interface)
                                usb_driver_release_interface(&ua101_driver,
                                                             intf);
                }
        }
}

static void ua101_card_free(struct snd_card *card)
{
        struct ua101 *ua = card->private_data;

        mutex_destroy(&ua->mutex);
}

static int ua101_probe(struct usb_interface *interface,
                       const struct usb_device_id *usb_id)
{
        static const struct snd_usb_midi_endpoint_info midi_ep = {
                .out_cables = 0x0001,
                .in_cables = 0x0001
        };
        static const struct snd_usb_audio_quirk midi_quirk = {
                .type = QUIRK_MIDI_FIXED_ENDPOINT,
                .data = &midi_ep
        };
        static const int intf_numbers[2][3] = {
                {       /* UA-101 */
                        [INTF_PLAYBACK] = 0,
                        [INTF_CAPTURE] = 1,
                        [INTF_MIDI] = 2,
                },
                {       /* UA-1000 */
                        [INTF_CAPTURE] = 1,
                        [INTF_PLAYBACK] = 2,
                        [INTF_MIDI] = 3,
                },
        };
        struct snd_card *card;
        struct ua101 *ua;
        unsigned int card_index, i;
        int is_ua1000;
        const char *name;
        char usb_path[32];
        int err;

        is_ua1000 = usb_id->idProduct == 0x0044;

        if (interface->altsetting->desc.bInterfaceNumber !=
            intf_numbers[is_ua1000][0])
                return -ENODEV;

        guard(mutex)(&devices_mutex);

        for (card_index = 0; card_index < SNDRV_CARDS; ++card_index)
                if (enable[card_index] && !(devices_used & (1 << card_index)))
                        break;
        if (card_index >= SNDRV_CARDS)
                return -ENOENT;
        err = snd_card_new(&interface->dev,
                           index[card_index], id[card_index], THIS_MODULE,
                           sizeof(*ua), &card);
        if (err < 0)
                return err;
        card->private_free = ua101_card_free;
        ua = card->private_data;
        ua->dev = interface_to_usbdev(interface);
        ua->card = card;
        ua->card_index = card_index;
        INIT_LIST_HEAD(&ua->midi_list);
        spin_lock_init(&ua->lock);
        mutex_init(&ua->mutex);
        INIT_LIST_HEAD(&ua->ready_playback_urbs);
        INIT_WORK(&ua->playback_work, playback_work);
        init_waitqueue_head(&ua->alsa_capture_wait);
        init_waitqueue_head(&ua->rate_feedback_wait);
        init_waitqueue_head(&ua->alsa_playback_wait);

        ua->intf[0] = interface;
        for (i = 1; i < ARRAY_SIZE(ua->intf); ++i) {
                ua->intf[i] = usb_ifnum_to_if(ua->dev,
                                              intf_numbers[is_ua1000][i]);
                if (!ua->intf[i]) {
                        dev_err(&ua->dev->dev, "interface %u not found\n",
                                intf_numbers[is_ua1000][i]);
                        err = -ENXIO;
                        goto probe_error;
                }
                err = usb_driver_claim_interface(&ua101_driver,
                                                 ua->intf[i], ua);
                if (err < 0) {
                        ua->intf[i] = NULL;
                        err = -EBUSY;
                        goto probe_error;
                }
        }

        err = detect_usb_format(ua);
        if (err < 0)
                goto probe_error;

        name = usb_id->idProduct == 0x0044 ? "UA-1000" : "UA-101";
        strscpy(card->driver, "UA-101");
        strscpy(card->shortname, name);
        usb_make_path(ua->dev, usb_path, sizeof(usb_path));
        snprintf(ua->card->longname, sizeof(ua->card->longname),
                 "EDIROL %s (serial %s), %u Hz at %s, %s speed", name,
                 ua->dev->serial ? ua->dev->serial : "?", ua->rate, usb_path,
                 ua->dev->speed == USB_SPEED_HIGH ? "high" : "full");

        err = alloc_stream_buffers(ua, &ua->capture);
        if (err < 0)
                goto probe_error;
        err = alloc_stream_buffers(ua, &ua->playback);
        if (err < 0)
                goto probe_error;

        err = alloc_stream_urbs(ua, &ua->capture, capture_urb_complete);
        if (err < 0)
                goto probe_error;
        err = alloc_stream_urbs(ua, &ua->playback, playback_urb_complete);
        if (err < 0)
                goto probe_error;

        err = snd_pcm_new(card, name, 0, 1, 1, &ua->pcm);
        if (err < 0)
                goto probe_error;
        ua->pcm->private_data = ua;
        strscpy(ua->pcm->name, name);
        snd_pcm_set_ops(ua->pcm, SNDRV_PCM_STREAM_PLAYBACK, &playback_pcm_ops);
        snd_pcm_set_ops(ua->pcm, SNDRV_PCM_STREAM_CAPTURE, &capture_pcm_ops);
        snd_pcm_set_managed_buffer_all(ua->pcm, SNDRV_DMA_TYPE_VMALLOC,
                                       NULL, 0, 0);

        err = snd_usbmidi_create(card, ua->intf[INTF_MIDI],
                                 &ua->midi_list, &midi_quirk);
        if (err < 0)
                goto probe_error;

        err = snd_card_register(card);
        if (err < 0)
                goto probe_error;

        usb_set_intfdata(interface, ua);
        devices_used |= 1 << card_index;

        return 0;

probe_error:
        free_usb_related_resources(ua, interface);
        snd_card_free(card);
        return err;
}

static void ua101_disconnect(struct usb_interface *interface)
{
        struct ua101 *ua = usb_get_intfdata(interface);
        struct list_head *midi;

        if (!ua)
                return;

        guard(mutex)(&devices_mutex);

        set_bit(DISCONNECTED, &ua->states);
        wake_up(&ua->rate_feedback_wait);

        /* make sure that userspace cannot create new requests */
        snd_card_disconnect(ua->card);

        /* make sure that there are no pending USB requests */
        list_for_each(midi, &ua->midi_list)
                snd_usbmidi_disconnect(midi);
        abort_alsa_playback(ua);
        abort_alsa_capture(ua);
        scoped_guard(mutex, &ua->mutex) {
                stop_usb_playback(ua);
                stop_usb_capture(ua);
        }

        free_usb_related_resources(ua, interface);

        devices_used &= ~(1 << ua->card_index);

        snd_card_free_when_closed(ua->card);
}

static const struct usb_device_id ua101_ids[] = {
        { USB_DEVICE(0x0582, 0x0044) }, /* UA-1000 high speed */
        { USB_DEVICE(0x0582, 0x007d) }, /* UA-101 high speed */
        { USB_DEVICE(0x0582, 0x008d) }, /* UA-101 full speed */
        { }
};
MODULE_DEVICE_TABLE(usb, ua101_ids);

static struct usb_driver ua101_driver = {
        .name = "snd-ua101",
        .id_table = ua101_ids,
        .probe = ua101_probe,
        .disconnect = ua101_disconnect,
#if 0
        .suspend = ua101_suspend,
        .resume = ua101_resume,
#endif
};

module_usb_driver(ua101_driver);