kernel_optimize_test/sound/usb/card.c
Takashi Iwai 92a586bdc0 ALSA: usb-audio: Fix races at disconnection and PCM closing
When a USB-audio device is disconnected while PCM is still running, we
still see some race: the disconnect callback calls
snd_usb_endpoint_free() that calls release_urbs() and then kfree()
while a PCM stream would be closed at the same time and calls
stop_endpoints() that leads to wait_clear_urbs().  That is, the EP
object might be deallocated while a PCM stream is syncing with
wait_clear_urbs() with the same EP.

Basically calling multiple wait_clear_urbs() would work fine, also
calling wait_clear_urbs() and release_urbs() would work, too, as
wait_clear_urbs() just reads some fields in ep.  The problem is the
succeeding kfree() in snd_pcm_endpoint_free().

This patch moves out the EP deallocation into the later point, the
destructor callback.  At this stage, all PCMs must have been already
closed, so it's safe to free the objects.

Reported-by: Alan Stern <stern@rowland.harvard.edu>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
2014-06-26 10:33:35 +02:00

783 lines
20 KiB
C

/*
* (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 device_setup[SNDRV_CARDS]; /* device parameter for this card */
static bool ignore_ctl_error;
static bool autoclock = true;
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_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.");
module_param(autoclock, bool, 0444);
MODULE_PARM_DESC(autoclock, "Enable auto-clock selection for UAC2 devices (default: yes).");
/*
* 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) {
dev_err(&dev->dev, "%u:%d : does not exist\n",
ctrlif, interface);
return -EINVAL;
}
alts = &iface->altsetting[0];
altsd = get_iface_desc(alts);
/*
* Android with both accessory and audio interfaces enabled gets the
* interface numbers wrong.
*/
if ((chip->usb_id == USB_ID(0x18d1, 0x2d04) ||
chip->usb_id == USB_ID(0x18d1, 0x2d05)) &&
interface == 0 &&
altsd->bInterfaceClass == USB_CLASS_VENDOR_SPEC &&
altsd->bInterfaceSubClass == USB_SUBCLASS_VENDOR_SPEC) {
interface = 2;
iface = usb_ifnum_to_if(dev, interface);
if (!iface)
return -EINVAL;
alts = &iface->altsetting[0];
altsd = get_iface_desc(alts);
}
if (usb_interface_claimed(iface)) {
dev_dbg(&dev->dev, "%d:%d: skipping, already claimed\n",
ctrlif, interface);
return -EINVAL;
}
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) {
dev_err(&dev->dev,
"%u:%d: cannot create sequencer device\n",
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) {
dev_dbg(&dev->dev,
"%u:%d: skipping non-supported interface %d\n",
ctrlif, interface, altsd->bInterfaceClass);
/* skip non-supported classes */
return -EINVAL;
}
if (snd_usb_get_speed(dev) == USB_SPEED_LOW) {
dev_err(&dev->dev, "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) {
dev_err(&dev->dev, "cannot find UAC_HEADER\n");
return -EINVAL;
}
switch (protocol) {
default:
dev_warn(&dev->dev,
"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) {
dev_info(&dev->dev, "skipping empty audio interface (v1)\n");
return -EINVAL;
}
if (h1->bLength < sizeof(*h1) + h1->bInCollection) {
dev_err(&dev->dev, "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) {
dev_err(&dev->dev, "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)
{
struct list_head *p, *n;
list_for_each_safe(p, n, &chip->ep_list)
snd_usb_endpoint_free(p);
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_interface *intf,
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_WIRELESS:
case USB_SPEED_SUPER:
break;
default:
dev_err(&dev->dev, "unknown device speed %d\n", snd_usb_get_speed(dev));
return -ENXIO;
}
err = snd_card_new(&intf->dev, index[idx], id[idx], THIS_MODULE,
0, &card);
if (err < 0) {
dev_err(&dev->dev, "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->autoclock = autoclock;
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) {
dev_err(&dev->dev, "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(intf, dev, i, quirk,
&chip) < 0) {
goto __error;
}
chip->pm_intf = intf;
break;
}
if (!chip) {
dev_err(&dev->dev, "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;
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) {
struct snd_usb_endpoint *ep;
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_entry(ep, &chip->ep_list, list) {
snd_usb_endpoint_release(ep);
}
/* 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 && chip->in_pm)
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 && !chip->in_pm)
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 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_entry(as, &chip->pcm_list, 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;
}
if (chip->num_suspended_intf == 1)
list_for_each_entry(mixer, &chip->mixer_list, list)
snd_usb_mixer_suspend(mixer);
return 0;
}
static int __usb_audio_resume(struct usb_interface *intf, bool reset_resume)
{
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;
chip->in_pm = 1;
/*
* 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_resume(mixer, reset_resume);
if (err < 0)
goto err_out;
}
if (!chip->autosuspended)
snd_power_change_state(chip->card, SNDRV_CTL_POWER_D0);
chip->autosuspended = 0;
err_out:
chip->in_pm = 0;
return err;
}
static int usb_audio_resume(struct usb_interface *intf)
{
return __usb_audio_resume(intf, false);
}
static int usb_audio_reset_resume(struct usb_interface *intf)
{
return __usb_audio_resume(intf, true);
}
#else
#define usb_audio_suspend NULL
#define usb_audio_resume NULL
#define usb_audio_reset_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,
.reset_resume = usb_audio_reset_resume,
.id_table = usb_audio_ids,
.supports_autosuspend = 1,
};
module_usb_driver(usb_audio_driver);