/*
 *   (Tentative) USB Audio Driver for ALSA
 *
 *   Copyright (c) 2002 by Takashi Iwai <tiwai@suse.de>
 *
 *   Many codes borrowed from audio.c by
 *          Alan Cox (alan@lxorguk.ukuu.org.uk)
 *          Thomas Sailer (sailer@ife.ee.ethz.ch)
 *
 *
 *   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
 *
 *
 *  NOTES:
 *
 *   - the linked URBs would be preferred but not used so far because of
 *     the instability of unlinking.
 *   - type II is not supported properly.  there is no device which supports
 *     this type *correctly*.  SB extigy looks as if it supports, but it's
 *     indeed an AC3 stream packed in SPDIF frames (i.e. no real AC3 stream).
 */


#include <linux/bitops.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/ctype.h>
#include <linux/usb.h>
#include <linux/moduleparam.h>
#include <linux/mutex.h>
#include <linux/usb/audio.h>
#include <linux/usb/audio-v2.h>
#include <linux/module.h>

#include <sound/control.h>
#include <sound/core.h>
#include <sound/info.h>
#include <sound/pcm.h>
#include <sound/pcm_params.h>
#include <sound/initval.h>

#include "usbaudio.h"
#include "card.h"
#include "midi.h"
#include "mixer.h"
#include "proc.h"
#include "quirks.h"
#include "endpoint.h"
#include "helper.h"
#include "debug.h"
#include "pcm.h"
#include "format.h"
#include "power.h"
#include "stream.h"

MODULE_AUTHOR("Takashi Iwai <tiwai@suse.de>");
MODULE_DESCRIPTION("USB Audio");
MODULE_LICENSE("GPL");
MODULE_SUPPORTED_DEVICE("{{Generic,USB Audio}}");


static int index[SNDRV_CARDS] = SNDRV_DEFAULT_IDX;      /* Index 0-MAX */
static char *id[SNDRV_CARDS] = SNDRV_DEFAULT_STR;       /* ID for this card */
static bool enable[SNDRV_CARDS] = SNDRV_DEFAULT_ENABLE_PNP;/* Enable this card */
/* Vendor/product IDs for this card */
static int vid[SNDRV_CARDS] = { [0 ... (SNDRV_CARDS-1)] = -1 };
static int pid[SNDRV_CARDS] = { [0 ... (SNDRV_CARDS-1)] = -1 };
static int nrpacks = 8;         /* max. number of packets per urb */
static int device_setup[SNDRV_CARDS]; /* device parameter for this card */
static bool ignore_ctl_error;

module_param_array(index, int, NULL, 0444);
MODULE_PARM_DESC(index, "Index value for the USB audio adapter.");
module_param_array(id, charp, NULL, 0444);
MODULE_PARM_DESC(id, "ID string for the USB audio adapter.");
module_param_array(enable, bool, NULL, 0444);
MODULE_PARM_DESC(enable, "Enable USB audio adapter.");
module_param_array(vid, int, NULL, 0444);
MODULE_PARM_DESC(vid, "Vendor ID for the USB audio device.");
module_param_array(pid, int, NULL, 0444);
MODULE_PARM_DESC(pid, "Product ID for the USB audio device.");
module_param(nrpacks, int, 0644);
MODULE_PARM_DESC(nrpacks, "Max. number of packets per URB.");
module_param_array(device_setup, int, NULL, 0444);
MODULE_PARM_DESC(device_setup, "Specific device setup (if needed).");
module_param(ignore_ctl_error, bool, 0444);
MODULE_PARM_DESC(ignore_ctl_error,
                 "Ignore errors from USB controller for mixer interfaces.");

/*
 * we keep the snd_usb_audio_t instances by ourselves for merging
 * the all interfaces on the same card as one sound device.
 */

static DEFINE_MUTEX(register_mutex);
static struct snd_usb_audio *usb_chip[SNDRV_CARDS];
static struct usb_driver usb_audio_driver;

/*
 * disconnect streams
 * called from snd_usb_audio_disconnect()
 */
static void snd_usb_stream_disconnect(struct list_head *head)
{
        int idx;
        struct snd_usb_stream *as;
        struct snd_usb_substream *subs;

        as = list_entry(head, struct snd_usb_stream, list);
        for (idx = 0; idx < 2; idx++) {
                subs = &as->substream[idx];
                if (!subs->num_formats)
                        continue;
                subs->interface = -1;
                subs->data_endpoint = NULL;
                subs->sync_endpoint = NULL;
        }
}

static int snd_usb_create_stream(struct snd_usb_audio *chip, int ctrlif, int interface)
{
        struct usb_device *dev = chip->dev;
        struct usb_host_interface *alts;
        struct usb_interface_descriptor *altsd;
        struct usb_interface *iface = usb_ifnum_to_if(dev, interface);

        if (!iface) {
                snd_printk(KERN_ERR "%d:%u:%d : does not exist\n",
                           dev->devnum, ctrlif, interface);
                return -EINVAL;
        }

        if (usb_interface_claimed(iface)) {
                snd_printdd(KERN_INFO "%d:%d:%d: skipping, already claimed\n",
                                                dev->devnum, ctrlif, interface);
                return -EINVAL;
        }

        alts = &iface->altsetting[0];
        altsd = get_iface_desc(alts);
        if ((altsd->bInterfaceClass == USB_CLASS_AUDIO ||
             altsd->bInterfaceClass == USB_CLASS_VENDOR_SPEC) &&
            altsd->bInterfaceSubClass == USB_SUBCLASS_MIDISTREAMING) {
                int err = snd_usbmidi_create(chip->card, iface,
                                             &chip->midi_list, NULL);
                if (err < 0) {
                        snd_printk(KERN_ERR "%d:%u:%d: cannot create sequencer device\n",
                                                dev->devnum, ctrlif, interface);
                        return -EINVAL;
                }
                usb_driver_claim_interface(&usb_audio_driver, iface, (void *)-1L);

                return 0;
        }

        if ((altsd->bInterfaceClass != USB_CLASS_AUDIO &&
             altsd->bInterfaceClass != USB_CLASS_VENDOR_SPEC) ||
            altsd->bInterfaceSubClass != USB_SUBCLASS_AUDIOSTREAMING) {
                snd_printdd(KERN_ERR "%d:%u:%d: skipping non-supported interface %d\n",
                                        dev->devnum, ctrlif, interface, altsd->bInterfaceClass);
                /* skip non-supported classes */
                return -EINVAL;
        }

        if (snd_usb_get_speed(dev) == USB_SPEED_LOW) {
                snd_printk(KERN_ERR "low speed audio streaming not supported\n");
                return -EINVAL;
        }

        if (! snd_usb_parse_audio_interface(chip, interface)) {
                usb_set_interface(dev, interface, 0); /* reset the current interface */
                usb_driver_claim_interface(&usb_audio_driver, iface, (void *)-1L);
                return -EINVAL;
        }

        return 0;
}

/*
 * parse audio control descriptor and create pcm/midi streams
 */
static int snd_usb_create_streams(struct snd_usb_audio *chip, int ctrlif)
{
        struct usb_device *dev = chip->dev;
        struct usb_host_interface *host_iface;
        struct usb_interface_descriptor *altsd;
        void *control_header;
        int i, protocol;

        /* find audiocontrol interface */
        host_iface = &usb_ifnum_to_if(dev, ctrlif)->altsetting[0];
        control_header = snd_usb_find_csint_desc(host_iface->extra,
                                                 host_iface->extralen,
                                                 NULL, UAC_HEADER);
        altsd = get_iface_desc(host_iface);
        protocol = altsd->bInterfaceProtocol;

        if (!control_header) {
                snd_printk(KERN_ERR "cannot find UAC_HEADER\n");
                return -EINVAL;
        }

        switch (protocol) {
        default:
                snd_printdd(KERN_WARNING "unknown interface protocol %#02x, assuming v1\n",
                            protocol);
                /* fall through */

        case UAC_VERSION_1: {
                struct uac1_ac_header_descriptor *h1 = control_header;

                if (!h1->bInCollection) {
                        snd_printk(KERN_INFO "skipping empty audio interface (v1)\n");
                        return -EINVAL;
                }

                if (h1->bLength < sizeof(*h1) + h1->bInCollection) {
                        snd_printk(KERN_ERR "invalid UAC_HEADER (v1)\n");
                        return -EINVAL;
                }

                for (i = 0; i < h1->bInCollection; i++)
                        snd_usb_create_stream(chip, ctrlif, h1->baInterfaceNr[i]);

                break;
        }

        case UAC_VERSION_2: {
                struct usb_interface_assoc_descriptor *assoc =
                        usb_ifnum_to_if(dev, ctrlif)->intf_assoc;

                if (!assoc) {
                        /*
                         * Firmware writers cannot count to three.  So to find
                         * the IAD on the NuForce UDH-100, also check the next
                         * interface.
                         */
                        struct usb_interface *iface =
                                usb_ifnum_to_if(dev, ctrlif + 1);
                        if (iface &&
                            iface->intf_assoc &&
                            iface->intf_assoc->bFunctionClass == USB_CLASS_AUDIO &&
                            iface->intf_assoc->bFunctionProtocol == UAC_VERSION_2)
                                assoc = iface->intf_assoc;
                }

                if (!assoc) {
                        snd_printk(KERN_ERR "Audio class v2 interfaces need an interface association\n");
                        return -EINVAL;
                }

                for (i = 0; i < assoc->bInterfaceCount; i++) {
                        int intf = assoc->bFirstInterface + i;

                        if (intf != ctrlif)
                                snd_usb_create_stream(chip, ctrlif, intf);
                }

                break;
        }
        }

        return 0;
}

/*
 * free the chip instance
 *
 * here we have to do not much, since pcm and controls are already freed
 *
 */

static int snd_usb_audio_free(struct snd_usb_audio *chip)
{
        mutex_destroy(&chip->mutex);
        kfree(chip);
        return 0;
}

static int snd_usb_audio_dev_free(struct snd_device *device)
{
        struct snd_usb_audio *chip = device->device_data;
        return snd_usb_audio_free(chip);
}

static void remove_trailing_spaces(char *str)
{
        char *p;

        if (!*str)
                return;
        for (p = str + strlen(str) - 1; p >= str && isspace(*p); p--)
                *p = 0;
}

/*
 * create a chip instance and set its names.
 */
static int snd_usb_audio_create(struct usb_device *dev, int idx,
                                const struct snd_usb_audio_quirk *quirk,
                                struct snd_usb_audio **rchip)
{
        struct snd_card *card;
        struct snd_usb_audio *chip;
        int err, len;
        char component[14];
        static struct snd_device_ops ops = {
                .dev_free =     snd_usb_audio_dev_free,
        };

        *rchip = NULL;

        switch (snd_usb_get_speed(dev)) {
        case USB_SPEED_LOW:
        case USB_SPEED_FULL:
        case USB_SPEED_HIGH:
        case USB_SPEED_SUPER:
                break;
        default:
                snd_printk(KERN_ERR "unknown device speed %d\n", snd_usb_get_speed(dev));
                return -ENXIO;
        }

        err = snd_card_create(index[idx], id[idx], THIS_MODULE, 0, &card);
        if (err < 0) {
                snd_printk(KERN_ERR "cannot create card instance %d\n", idx);
                return err;
        }

        chip = kzalloc(sizeof(*chip), GFP_KERNEL);
        if (! chip) {
                snd_card_free(card);
                return -ENOMEM;
        }

        mutex_init(&chip->mutex);
        init_rwsem(&chip->shutdown_rwsem);
        chip->index = idx;
        chip->dev = dev;
        chip->card = card;
        chip->setup = device_setup[idx];
        chip->nrpacks = nrpacks;
        chip->probing = 1;

        chip->usb_id = USB_ID(le16_to_cpu(dev->descriptor.idVendor),
                              le16_to_cpu(dev->descriptor.idProduct));
        INIT_LIST_HEAD(&chip->pcm_list);
        INIT_LIST_HEAD(&chip->ep_list);
        INIT_LIST_HEAD(&chip->midi_list);
        INIT_LIST_HEAD(&chip->mixer_list);

        if ((err = snd_device_new(card, SNDRV_DEV_LOWLEVEL, chip, &ops)) < 0) {
                snd_usb_audio_free(chip);
                snd_card_free(card);
                return err;
        }

        strcpy(card->driver, "USB-Audio");
        sprintf(component, "USB%04x:%04x",
                USB_ID_VENDOR(chip->usb_id), USB_ID_PRODUCT(chip->usb_id));
        snd_component_add(card, component);

        /* retrieve the device string as shortname */
        if (quirk && quirk->product_name && *quirk->product_name) {
                strlcpy(card->shortname, quirk->product_name, sizeof(card->shortname));
        } else {
                if (!dev->descriptor.iProduct ||
                    usb_string(dev, dev->descriptor.iProduct,
                    card->shortname, sizeof(card->shortname)) <= 0) {
                        /* no name available from anywhere, so use ID */
                        sprintf(card->shortname, "USB Device %#04x:%#04x",
                                USB_ID_VENDOR(chip->usb_id),
                                USB_ID_PRODUCT(chip->usb_id));
                }
        }
        remove_trailing_spaces(card->shortname);

        /* retrieve the vendor and device strings as longname */
        if (quirk && quirk->vendor_name && *quirk->vendor_name) {
                len = strlcpy(card->longname, quirk->vendor_name, sizeof(card->longname));
        } else {
                if (dev->descriptor.iManufacturer)
                        len = usb_string(dev, dev->descriptor.iManufacturer,
                                         card->longname, sizeof(card->longname));
                else
                        len = 0;
                /* we don't really care if there isn't any vendor string */
        }
        if (len > 0) {
                remove_trailing_spaces(card->longname);
                if (*card->longname)
                        strlcat(card->longname, " ", sizeof(card->longname));
        }

        strlcat(card->longname, card->shortname, sizeof(card->longname));

        len = strlcat(card->longname, " at ", sizeof(card->longname));

        if (len < sizeof(card->longname))
                usb_make_path(dev, card->longname + len, sizeof(card->longname) - len);

        switch (snd_usb_get_speed(dev)) {
        case USB_SPEED_LOW:
                strlcat(card->longname, ", low speed", sizeof(card->longname));
                break;
        case USB_SPEED_FULL:
                strlcat(card->longname, ", full speed", sizeof(card->longname));
                break;
        case USB_SPEED_HIGH:
                strlcat(card->longname, ", high speed", sizeof(card->longname));
                break;
        case USB_SPEED_SUPER:
                strlcat(card->longname, ", super speed", sizeof(card->longname));
                break;
        default:
                break;
        }

        snd_usb_audio_create_proc(chip);

        *rchip = chip;
        return 0;
}

/*
 * probe the active usb device
 *
 * note that this can be called multiple times per a device, when it
 * includes multiple audio control interfaces.
 *
 * thus we check the usb device pointer and creates the card instance
 * only at the first time.  the successive calls of this function will
 * append the pcm interface to the corresponding card.
 */
static struct snd_usb_audio *
snd_usb_audio_probe(struct usb_device *dev,
                    struct usb_interface *intf,
                    const struct usb_device_id *usb_id)
{
        const struct snd_usb_audio_quirk *quirk = (const struct snd_usb_audio_quirk *)usb_id->driver_info;
        int i, err;
        struct snd_usb_audio *chip;
        struct usb_host_interface *alts;
        int ifnum;
        u32 id;

        alts = &intf->altsetting[0];
        ifnum = get_iface_desc(alts)->bInterfaceNumber;
        id = USB_ID(le16_to_cpu(dev->descriptor.idVendor),
                    le16_to_cpu(dev->descriptor.idProduct));
        if (quirk && quirk->ifnum >= 0 && ifnum != quirk->ifnum)
                goto __err_val;

        if (snd_usb_apply_boot_quirk(dev, intf, quirk) < 0)
                goto __err_val;

        /*
         * found a config.  now register to ALSA
         */

        /* check whether it's already registered */
        chip = NULL;
        mutex_lock(&register_mutex);
        for (i = 0; i < SNDRV_CARDS; i++) {
                if (usb_chip[i] && usb_chip[i]->dev == dev) {
                        if (usb_chip[i]->shutdown) {
                                snd_printk(KERN_ERR "USB device is in the shutdown state, cannot create a card instance\n");
                                goto __error;
                        }
                        chip = usb_chip[i];
                        chip->probing = 1;
                        break;
                }
        }
        if (! chip) {
                /* it's a fresh one.
                 * now look for an empty slot and create a new card instance
                 */
                for (i = 0; i < SNDRV_CARDS; i++)
                        if (enable[i] && ! usb_chip[i] &&
                            (vid[i] == -1 || vid[i] == USB_ID_VENDOR(id)) &&
                            (pid[i] == -1 || pid[i] == USB_ID_PRODUCT(id))) {
                                if (snd_usb_audio_create(dev, i, quirk, &chip) < 0) {
                                        goto __error;
                                }
                                snd_card_set_dev(chip->card, &intf->dev);
                                chip->pm_intf = intf;
                                break;
                        }
                if (!chip) {
                        printk(KERN_ERR "no available usb audio device\n");
                        goto __error;
                }
        }

        /*
         * For devices with more than one control interface, we assume the
         * first contains the audio controls. We might need a more specific
         * check here in the future.
         */
        if (!chip->ctrl_intf)
                chip->ctrl_intf = alts;

        chip->txfr_quirk = 0;
        err = 1; /* continue */
        if (quirk && quirk->ifnum != QUIRK_NO_INTERFACE) {
                /* need some special handlings */
                if ((err = snd_usb_create_quirk(chip, intf, &usb_audio_driver, quirk)) < 0)
                        goto __error;
        }

        if (err > 0) {
                /* create normal USB audio interfaces */
                if (snd_usb_create_streams(chip, ifnum) < 0 ||
                    snd_usb_create_mixer(chip, ifnum, ignore_ctl_error) < 0) {
                        goto __error;
                }
        }

        /* we are allowed to call snd_card_register() many times */
        if (snd_card_register(chip->card) < 0) {
                goto __error;
        }

        usb_chip[chip->index] = chip;
        chip->num_interfaces++;
        chip->probing = 0;
        mutex_unlock(&register_mutex);
        return chip;

 __error:
        if (chip) {
                if (!chip->num_interfaces)
                        snd_card_free(chip->card);
                chip->probing = 0;
        }
        mutex_unlock(&register_mutex);
 __err_val:
        return NULL;
}

/*
 * we need to take care of counter, since disconnection can be called also
 * many times as well as usb_audio_probe().
 */
static void snd_usb_audio_disconnect(struct usb_device *dev,
                                     struct snd_usb_audio *chip)
{
        struct snd_card *card;
        struct list_head *p, *n;

        if (chip == (void *)-1L)
                return;

        card = chip->card;
        down_write(&chip->shutdown_rwsem);
        chip->shutdown = 1;
        up_write(&chip->shutdown_rwsem);

        mutex_lock(&register_mutex);
        chip->num_interfaces--;
        if (chip->num_interfaces <= 0) {
                snd_card_disconnect(card);
                /* release the pcm resources */
                list_for_each(p, &chip->pcm_list) {
                        snd_usb_stream_disconnect(p);
                }
                /* release the endpoint resources */
                list_for_each_safe(p, n, &chip->ep_list) {
                        snd_usb_endpoint_free(p);
                }
                /* release the midi resources */
                list_for_each(p, &chip->midi_list) {
                        snd_usbmidi_disconnect(p);
                }
                /* release mixer resources */
                list_for_each(p, &chip->mixer_list) {
                        snd_usb_mixer_disconnect(p);
                }
                usb_chip[chip->index] = NULL;
                mutex_unlock(&register_mutex);
                snd_card_free_when_closed(card);
        } else {
                mutex_unlock(&register_mutex);
        }
}

/*
 * new 2.5 USB kernel API
 */
static int usb_audio_probe(struct usb_interface *intf,
                           const struct usb_device_id *id)
{
        struct snd_usb_audio *chip;
        chip = snd_usb_audio_probe(interface_to_usbdev(intf), intf, id);
        if (chip) {
                usb_set_intfdata(intf, chip);
                return 0;
        } else
                return -EIO;
}

static void usb_audio_disconnect(struct usb_interface *intf)
{
        snd_usb_audio_disconnect(interface_to_usbdev(intf),
                                 usb_get_intfdata(intf));
}

#ifdef CONFIG_PM

int snd_usb_autoresume(struct snd_usb_audio *chip)
{
        int err = -ENODEV;

        down_read(&chip->shutdown_rwsem);
        if (chip->probing)
                err = 0;
        else if (!chip->shutdown)
                err = usb_autopm_get_interface(chip->pm_intf);
        up_read(&chip->shutdown_rwsem);

        return err;
}

void snd_usb_autosuspend(struct snd_usb_audio *chip)
{
        down_read(&chip->shutdown_rwsem);
        if (!chip->shutdown && !chip->probing)
                usb_autopm_put_interface(chip->pm_intf);
        up_read(&chip->shutdown_rwsem);
}

static int usb_audio_suspend(struct usb_interface *intf, pm_message_t message)
{
        struct snd_usb_audio *chip = usb_get_intfdata(intf);
        struct list_head *p;
        struct snd_usb_stream *as;
        struct usb_mixer_interface *mixer;

        if (chip == (void *)-1L)
                return 0;

        if (!PMSG_IS_AUTO(message)) {
                snd_power_change_state(chip->card, SNDRV_CTL_POWER_D3hot);
                if (!chip->num_suspended_intf++) {
                        list_for_each(p, &chip->pcm_list) {
                                as = list_entry(p, struct snd_usb_stream, list);
                                snd_pcm_suspend_all(as->pcm);
                                as->substream[0].need_setup_ep =
                                        as->substream[1].need_setup_ep = true;
                        }
                }
        } else {
                /*
                 * otherwise we keep the rest of the system in the dark
                 * to keep this transparent
                 */
                if (!chip->num_suspended_intf++)
                        chip->autosuspended = 1;
        }

        list_for_each_entry(mixer, &chip->mixer_list, list)
                snd_usb_mixer_inactivate(mixer);

        return 0;
}

static int usb_audio_resume(struct usb_interface *intf)
{
        struct snd_usb_audio *chip = usb_get_intfdata(intf);
        struct usb_mixer_interface *mixer;
        int err = 0;

        if (chip == (void *)-1L)
                return 0;
        if (--chip->num_suspended_intf)
                return 0;
        /*
         * ALSA leaves material resumption to user space
         * we just notify and restart the mixers
         */
        list_for_each_entry(mixer, &chip->mixer_list, list) {
                err = snd_usb_mixer_activate(mixer);
                if (err < 0)
                        goto err_out;
        }

        if (!chip->autosuspended)
                snd_power_change_state(chip->card, SNDRV_CTL_POWER_D0);
        chip->autosuspended = 0;

err_out:
        return err;
}
#else
#define usb_audio_suspend       NULL
#define usb_audio_resume        NULL
#endif          /* CONFIG_PM */

static struct usb_device_id usb_audio_ids [] = {
#include "quirks-table.h"
    { .match_flags = (USB_DEVICE_ID_MATCH_INT_CLASS | USB_DEVICE_ID_MATCH_INT_SUBCLASS),
      .bInterfaceClass = USB_CLASS_AUDIO,
      .bInterfaceSubClass = USB_SUBCLASS_AUDIOCONTROL },
    { }                                         /* Terminating entry */
};

MODULE_DEVICE_TABLE (usb, usb_audio_ids);

/*
 * entry point for linux usb interface
 */

static struct usb_driver usb_audio_driver = {
        .name =         "snd-usb-audio",
        .probe =        usb_audio_probe,
        .disconnect =   usb_audio_disconnect,
        .suspend =      usb_audio_suspend,
        .resume =       usb_audio_resume,
        .id_table =     usb_audio_ids,
        .supports_autosuspend = 1,
};

static int __init snd_usb_audio_init(void)
{
        if (nrpacks < 1 || nrpacks > MAX_PACKS) {
                printk(KERN_WARNING "invalid nrpacks value.\n");
                return -EINVAL;
        }
        return usb_register(&usb_audio_driver);
}

static void __exit snd_usb_audio_cleanup(void)
{
        usb_deregister(&usb_audio_driver);
}

module_init(snd_usb_audio_init);
module_exit(snd_usb_audio_cleanup);