/*
   *   (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:
   *
   *   - async unlink should be used for avoiding the sleep inside lock.
   *     2.4.22 usb-uhci seems buggy for async unlinking and results in
   *     oops.  in such a cse, pass async_unlink=0 option.
   *   - 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 bool async_unlink = 1;

  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(async_unlink, bool, 0444);
  MODULE_PARM_DESC(async_unlink, "Use async unlink mode.");
  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;

  		snd_usb_release_substream_urbs(subs, 1);
  		subs->interface = -1;
  	}
  }
  
  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
  ",
  			   dev->devnum, ctrlif, interface);
  		return -EINVAL;
  	}
  
  	if (usb_interface_claimed(iface)) {
  		snd_printdd(KERN_INFO "%d:%d:%d: skipping, already claimed
  ",
  						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
  ",
  						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
  ",
  					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
  ");
  		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
  ");
  		return -EINVAL;
  	}
  
  	switch (protocol) {

  	default:
  		snd_printdd(KERN_WARNING "unknown interface protocol %#02x, assuming v1
  ",
  			    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)
  ");
  			return -EINVAL;
  		}
  
  		if (h1->bLength < sizeof(*h1) + h1->bInCollection) {
  			snd_printk(KERN_ERR "invalid UAC_HEADER (v1)
  ");
  			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) {
  			snd_printk(KERN_ERR "Audio class v2 interfaces need an interface association
  ");
  			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)
  {
  	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
  ", 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
  ", idx);
  		return err;
  	}
  
  	chip = kzalloc(sizeof(*chip), GFP_KERNEL);
  	if (! chip) {
  		snd_card_free(card);
  		return -ENOMEM;
  	}

  	mutex_init(&chip->shutdown_mutex);

  	chip->index = idx;
  	chip->dev = dev;
  	chip->card = card;
  	chip->setup = device_setup[idx];
  	chip->nrpacks = nrpacks;
  	chip->async_unlink = async_unlink;

  	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->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
  ");
  				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
  ");
  			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;
  	mutex_lock(&register_mutex);

  	mutex_lock(&chip->shutdown_mutex);

  	chip->shutdown = 1;
  	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 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(&chip->shutdown_mutex);

  		mutex_unlock(&register_mutex);
  		snd_card_free_when_closed(card);
  	} else {

  		mutex_unlock(&chip->shutdown_mutex);

  		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;
  
  	if (!chip->shutdown && !chip->probing)
  		err = usb_autopm_get_interface(chip->pm_intf);
  
  	return err;
  }
  
  void snd_usb_autosuspend(struct snd_usb_audio *chip)
  {
  	if (!chip->shutdown && !chip->probing)
  		usb_autopm_put_interface(chip->pm_intf);
  }

  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);
  			}
   		}
  	} 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.
  ");
  		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);