xref: /linux/sound/usb/card.c (revision 765532c8aaac624b5f8687af6d319c6a1138a257)
1 /*
2  *   (Tentative) USB Audio Driver for ALSA
3  *
4  *   Copyright (c) 2002 by Takashi Iwai <tiwai@suse.de>
5  *
6  *   Many codes borrowed from audio.c by
7  *	    Alan Cox (alan@lxorguk.ukuu.org.uk)
8  *	    Thomas Sailer (sailer@ife.ee.ethz.ch)
9  *
10  *
11  *   This program is free software; you can redistribute it and/or modify
12  *   it under the terms of the GNU General Public License as published by
13  *   the Free Software Foundation; either version 2 of the License, or
14  *   (at your option) any later version.
15  *
16  *   This program is distributed in the hope that it will be useful,
17  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
18  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
19  *   GNU General Public License for more details.
20  *
21  *   You should have received a copy of the GNU General Public License
22  *   along with this program; if not, write to the Free Software
23  *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
24  *
25  *
26  *  NOTES:
27  *
28  *   - async unlink should be used for avoiding the sleep inside lock.
29  *     2.4.22 usb-uhci seems buggy for async unlinking and results in
30  *     oops.  in such a cse, pass async_unlink=0 option.
31  *   - the linked URBs would be preferred but not used so far because of
32  *     the instability of unlinking.
33  *   - type II is not supported properly.  there is no device which supports
34  *     this type *correctly*.  SB extigy looks as if it supports, but it's
35  *     indeed an AC3 stream packed in SPDIF frames (i.e. no real AC3 stream).
36  */
37 
38 
39 #include <linux/bitops.h>
40 #include <linux/init.h>
41 #include <linux/list.h>
42 #include <linux/slab.h>
43 #include <linux/string.h>
44 #include <linux/usb.h>
45 #include <linux/moduleparam.h>
46 #include <linux/mutex.h>
47 #include <linux/usb/audio.h>
48 #include <linux/usb/audio-v2.h>
49 
50 #include <sound/core.h>
51 #include <sound/info.h>
52 #include <sound/pcm.h>
53 #include <sound/pcm_params.h>
54 #include <sound/initval.h>
55 
56 #include "usbaudio.h"
57 #include "card.h"
58 #include "midi.h"
59 #include "mixer.h"
60 #include "proc.h"
61 #include "quirks.h"
62 #include "endpoint.h"
63 #include "helper.h"
64 #include "debug.h"
65 #include "pcm.h"
66 #include "urb.h"
67 #include "format.h"
68 
69 MODULE_AUTHOR("Takashi Iwai <tiwai@suse.de>");
70 MODULE_DESCRIPTION("USB Audio");
71 MODULE_LICENSE("GPL");
72 MODULE_SUPPORTED_DEVICE("{{Generic,USB Audio}}");
73 
74 
75 static int index[SNDRV_CARDS] = SNDRV_DEFAULT_IDX;	/* Index 0-MAX */
76 static char *id[SNDRV_CARDS] = SNDRV_DEFAULT_STR;	/* ID for this card */
77 static int enable[SNDRV_CARDS] = SNDRV_DEFAULT_ENABLE_PNP;/* Enable this card */
78 /* Vendor/product IDs for this card */
79 static int vid[SNDRV_CARDS] = { [0 ... (SNDRV_CARDS-1)] = -1 };
80 static int pid[SNDRV_CARDS] = { [0 ... (SNDRV_CARDS-1)] = -1 };
81 static int nrpacks = 8;		/* max. number of packets per urb */
82 static int async_unlink = 1;
83 static int device_setup[SNDRV_CARDS]; /* device parameter for this card */
84 static int ignore_ctl_error;
85 
86 module_param_array(index, int, NULL, 0444);
87 MODULE_PARM_DESC(index, "Index value for the USB audio adapter.");
88 module_param_array(id, charp, NULL, 0444);
89 MODULE_PARM_DESC(id, "ID string for the USB audio adapter.");
90 module_param_array(enable, bool, NULL, 0444);
91 MODULE_PARM_DESC(enable, "Enable USB audio adapter.");
92 module_param_array(vid, int, NULL, 0444);
93 MODULE_PARM_DESC(vid, "Vendor ID for the USB audio device.");
94 module_param_array(pid, int, NULL, 0444);
95 MODULE_PARM_DESC(pid, "Product ID for the USB audio device.");
96 module_param(nrpacks, int, 0644);
97 MODULE_PARM_DESC(nrpacks, "Max. number of packets per URB.");
98 module_param(async_unlink, bool, 0444);
99 MODULE_PARM_DESC(async_unlink, "Use async unlink mode.");
100 module_param_array(device_setup, int, NULL, 0444);
101 MODULE_PARM_DESC(device_setup, "Specific device setup (if needed).");
102 module_param(ignore_ctl_error, bool, 0444);
103 MODULE_PARM_DESC(ignore_ctl_error,
104 		 "Ignore errors from USB controller for mixer interfaces.");
105 
106 /*
107  * we keep the snd_usb_audio_t instances by ourselves for merging
108  * the all interfaces on the same card as one sound device.
109  */
110 
111 static DEFINE_MUTEX(register_mutex);
112 static struct snd_usb_audio *usb_chip[SNDRV_CARDS];
113 static struct usb_driver usb_audio_driver;
114 
115 /*
116  * disconnect streams
117  * called from snd_usb_audio_disconnect()
118  */
119 static void snd_usb_stream_disconnect(struct list_head *head)
120 {
121 	int idx;
122 	struct snd_usb_stream *as;
123 	struct snd_usb_substream *subs;
124 
125 	as = list_entry(head, struct snd_usb_stream, list);
126 	for (idx = 0; idx < 2; idx++) {
127 		subs = &as->substream[idx];
128 		if (!subs->num_formats)
129 			continue;
130 		snd_usb_release_substream_urbs(subs, 1);
131 		subs->interface = -1;
132 	}
133 }
134 
135 static int snd_usb_create_stream(struct snd_usb_audio *chip, int ctrlif, int interface)
136 {
137 	struct usb_device *dev = chip->dev;
138 	struct usb_host_interface *alts;
139 	struct usb_interface_descriptor *altsd;
140 	struct usb_interface *iface = usb_ifnum_to_if(dev, interface);
141 
142 	if (!iface) {
143 		snd_printk(KERN_ERR "%d:%u:%d : does not exist\n",
144 			   dev->devnum, ctrlif, interface);
145 		return -EINVAL;
146 	}
147 
148 	if (usb_interface_claimed(iface)) {
149 		snd_printdd(KERN_INFO "%d:%d:%d: skipping, already claimed\n",
150 						dev->devnum, ctrlif, interface);
151 		return -EINVAL;
152 	}
153 
154 	alts = &iface->altsetting[0];
155 	altsd = get_iface_desc(alts);
156 	if ((altsd->bInterfaceClass == USB_CLASS_AUDIO ||
157 	     altsd->bInterfaceClass == USB_CLASS_VENDOR_SPEC) &&
158 	    altsd->bInterfaceSubClass == USB_SUBCLASS_MIDISTREAMING) {
159 		int err = snd_usbmidi_create(chip->card, iface,
160 					     &chip->midi_list, NULL);
161 		if (err < 0) {
162 			snd_printk(KERN_ERR "%d:%u:%d: cannot create sequencer device\n",
163 						dev->devnum, ctrlif, interface);
164 			return -EINVAL;
165 		}
166 		usb_driver_claim_interface(&usb_audio_driver, iface, (void *)-1L);
167 
168 		return 0;
169 	}
170 
171 	if ((altsd->bInterfaceClass != USB_CLASS_AUDIO &&
172 	     altsd->bInterfaceClass != USB_CLASS_VENDOR_SPEC) ||
173 	    altsd->bInterfaceSubClass != USB_SUBCLASS_AUDIOSTREAMING) {
174 		snd_printdd(KERN_ERR "%d:%u:%d: skipping non-supported interface %d\n",
175 					dev->devnum, ctrlif, interface, altsd->bInterfaceClass);
176 		/* skip non-supported classes */
177 		return -EINVAL;
178 	}
179 
180 	if (snd_usb_get_speed(dev) == USB_SPEED_LOW) {
181 		snd_printk(KERN_ERR "low speed audio streaming not supported\n");
182 		return -EINVAL;
183 	}
184 
185 	if (! snd_usb_parse_audio_endpoints(chip, interface)) {
186 		usb_set_interface(dev, interface, 0); /* reset the current interface */
187 		usb_driver_claim_interface(&usb_audio_driver, iface, (void *)-1L);
188 		return -EINVAL;
189 	}
190 
191 	return 0;
192 }
193 
194 /*
195  * parse audio control descriptor and create pcm/midi streams
196  */
197 static int snd_usb_create_streams(struct snd_usb_audio *chip, int ctrlif)
198 {
199 	struct usb_device *dev = chip->dev;
200 	struct usb_host_interface *host_iface;
201 	struct usb_interface_descriptor *altsd;
202 	void *control_header;
203 	int i, protocol;
204 
205 	/* find audiocontrol interface */
206 	host_iface = &usb_ifnum_to_if(dev, ctrlif)->altsetting[0];
207 	control_header = snd_usb_find_csint_desc(host_iface->extra,
208 						 host_iface->extralen,
209 						 NULL, UAC_HEADER);
210 	altsd = get_iface_desc(host_iface);
211 	protocol = altsd->bInterfaceProtocol;
212 
213 	if (!control_header) {
214 		snd_printk(KERN_ERR "cannot find UAC_HEADER\n");
215 		return -EINVAL;
216 	}
217 
218 	switch (protocol) {
219 	default:
220 		snd_printdd(KERN_WARNING "unknown interface protocol %#02x, assuming v1\n",
221 			    protocol);
222 		/* fall through */
223 
224 	case UAC_VERSION_1: {
225 		struct uac1_ac_header_descriptor *h1 = control_header;
226 
227 		if (!h1->bInCollection) {
228 			snd_printk(KERN_INFO "skipping empty audio interface (v1)\n");
229 			return -EINVAL;
230 		}
231 
232 		if (h1->bLength < sizeof(*h1) + h1->bInCollection) {
233 			snd_printk(KERN_ERR "invalid UAC_HEADER (v1)\n");
234 			return -EINVAL;
235 		}
236 
237 		for (i = 0; i < h1->bInCollection; i++)
238 			snd_usb_create_stream(chip, ctrlif, h1->baInterfaceNr[i]);
239 
240 		break;
241 	}
242 
243 	case UAC_VERSION_2: {
244 		struct usb_interface_assoc_descriptor *assoc =
245 			usb_ifnum_to_if(dev, ctrlif)->intf_assoc;
246 
247 		if (!assoc) {
248 			snd_printk(KERN_ERR "Audio class v2 interfaces need an interface association\n");
249 			return -EINVAL;
250 		}
251 
252 		for (i = 0; i < assoc->bInterfaceCount; i++) {
253 			int intf = assoc->bFirstInterface + i;
254 
255 			if (intf != ctrlif)
256 				snd_usb_create_stream(chip, ctrlif, intf);
257 		}
258 
259 		break;
260 	}
261 	}
262 
263 	return 0;
264 }
265 
266 /*
267  * free the chip instance
268  *
269  * here we have to do not much, since pcm and controls are already freed
270  *
271  */
272 
273 static int snd_usb_audio_free(struct snd_usb_audio *chip)
274 {
275 	kfree(chip);
276 	return 0;
277 }
278 
279 static int snd_usb_audio_dev_free(struct snd_device *device)
280 {
281 	struct snd_usb_audio *chip = device->device_data;
282 	return snd_usb_audio_free(chip);
283 }
284 
285 
286 /*
287  * create a chip instance and set its names.
288  */
289 static int snd_usb_audio_create(struct usb_device *dev, int idx,
290 				const struct snd_usb_audio_quirk *quirk,
291 				struct snd_usb_audio **rchip)
292 {
293 	struct snd_card *card;
294 	struct snd_usb_audio *chip;
295 	int err, len;
296 	char component[14];
297 	static struct snd_device_ops ops = {
298 		.dev_free =	snd_usb_audio_dev_free,
299 	};
300 
301 	*rchip = NULL;
302 
303 	switch (snd_usb_get_speed(dev)) {
304 	case USB_SPEED_LOW:
305 	case USB_SPEED_FULL:
306 	case USB_SPEED_HIGH:
307 	case USB_SPEED_SUPER:
308 		break;
309 	default:
310 		snd_printk(KERN_ERR "unknown device speed %d\n", snd_usb_get_speed(dev));
311 		return -ENXIO;
312 	}
313 
314 	err = snd_card_create(index[idx], id[idx], THIS_MODULE, 0, &card);
315 	if (err < 0) {
316 		snd_printk(KERN_ERR "cannot create card instance %d\n", idx);
317 		return err;
318 	}
319 
320 	chip = kzalloc(sizeof(*chip), GFP_KERNEL);
321 	if (! chip) {
322 		snd_card_free(card);
323 		return -ENOMEM;
324 	}
325 
326 	chip->index = idx;
327 	chip->dev = dev;
328 	chip->card = card;
329 	chip->setup = device_setup[idx];
330 	chip->nrpacks = nrpacks;
331 	chip->async_unlink = async_unlink;
332 
333 	chip->usb_id = USB_ID(le16_to_cpu(dev->descriptor.idVendor),
334 			      le16_to_cpu(dev->descriptor.idProduct));
335 	INIT_LIST_HEAD(&chip->pcm_list);
336 	INIT_LIST_HEAD(&chip->midi_list);
337 	INIT_LIST_HEAD(&chip->mixer_list);
338 
339 	if ((err = snd_device_new(card, SNDRV_DEV_LOWLEVEL, chip, &ops)) < 0) {
340 		snd_usb_audio_free(chip);
341 		snd_card_free(card);
342 		return err;
343 	}
344 
345 	strcpy(card->driver, "USB-Audio");
346 	sprintf(component, "USB%04x:%04x",
347 		USB_ID_VENDOR(chip->usb_id), USB_ID_PRODUCT(chip->usb_id));
348 	snd_component_add(card, component);
349 
350 	/* retrieve the device string as shortname */
351 	if (quirk && quirk->product_name) {
352 		strlcpy(card->shortname, quirk->product_name, sizeof(card->shortname));
353 	} else {
354 		if (!dev->descriptor.iProduct ||
355 		    usb_string(dev, dev->descriptor.iProduct,
356 		    card->shortname, sizeof(card->shortname)) <= 0) {
357 			/* no name available from anywhere, so use ID */
358 			sprintf(card->shortname, "USB Device %#04x:%#04x",
359 				USB_ID_VENDOR(chip->usb_id),
360 				USB_ID_PRODUCT(chip->usb_id));
361 		}
362 	}
363 
364 	/* retrieve the vendor and device strings as longname */
365 	if (quirk && quirk->vendor_name) {
366 		len = strlcpy(card->longname, quirk->vendor_name, sizeof(card->longname));
367 	} else {
368 		if (dev->descriptor.iManufacturer)
369 			len = usb_string(dev, dev->descriptor.iManufacturer,
370 					 card->longname, sizeof(card->longname));
371 		else
372 			len = 0;
373 		/* we don't really care if there isn't any vendor string */
374 	}
375 	if (len > 0)
376 		strlcat(card->longname, " ", sizeof(card->longname));
377 
378 	strlcat(card->longname, card->shortname, sizeof(card->longname));
379 
380 	len = strlcat(card->longname, " at ", sizeof(card->longname));
381 
382 	if (len < sizeof(card->longname))
383 		usb_make_path(dev, card->longname + len, sizeof(card->longname) - len);
384 
385 	switch (snd_usb_get_speed(dev)) {
386 	case USB_SPEED_LOW:
387 		strlcat(card->longname, ", low speed", sizeof(card->longname));
388 		break;
389 	case USB_SPEED_FULL:
390 		strlcat(card->longname, ", full speed", sizeof(card->longname));
391 		break;
392 	case USB_SPEED_HIGH:
393 		strlcat(card->longname, ", high speed", sizeof(card->longname));
394 		break;
395 	case USB_SPEED_SUPER:
396 		strlcat(card->longname, ", super speed", sizeof(card->longname));
397 		break;
398 	default:
399 		break;
400 	}
401 
402 	snd_usb_audio_create_proc(chip);
403 
404 	*rchip = chip;
405 	return 0;
406 }
407 
408 /*
409  * probe the active usb device
410  *
411  * note that this can be called multiple times per a device, when it
412  * includes multiple audio control interfaces.
413  *
414  * thus we check the usb device pointer and creates the card instance
415  * only at the first time.  the successive calls of this function will
416  * append the pcm interface to the corresponding card.
417  */
418 static void *snd_usb_audio_probe(struct usb_device *dev,
419 				 struct usb_interface *intf,
420 				 const struct usb_device_id *usb_id)
421 {
422 	const struct snd_usb_audio_quirk *quirk = (const struct snd_usb_audio_quirk *)usb_id->driver_info;
423 	int i, err;
424 	struct snd_usb_audio *chip;
425 	struct usb_host_interface *alts;
426 	int ifnum;
427 	u32 id;
428 
429 	alts = &intf->altsetting[0];
430 	ifnum = get_iface_desc(alts)->bInterfaceNumber;
431 	id = USB_ID(le16_to_cpu(dev->descriptor.idVendor),
432 		    le16_to_cpu(dev->descriptor.idProduct));
433 	if (quirk && quirk->ifnum >= 0 && ifnum != quirk->ifnum)
434 		goto __err_val;
435 
436 	if (snd_usb_apply_boot_quirk(dev, intf, quirk) < 0)
437 		goto __err_val;
438 
439 	/*
440 	 * found a config.  now register to ALSA
441 	 */
442 
443 	/* check whether it's already registered */
444 	chip = NULL;
445 	mutex_lock(&register_mutex);
446 	for (i = 0; i < SNDRV_CARDS; i++) {
447 		if (usb_chip[i] && usb_chip[i]->dev == dev) {
448 			if (usb_chip[i]->shutdown) {
449 				snd_printk(KERN_ERR "USB device is in the shutdown state, cannot create a card instance\n");
450 				goto __error;
451 			}
452 			chip = usb_chip[i];
453 			break;
454 		}
455 	}
456 	if (! chip) {
457 		/* it's a fresh one.
458 		 * now look for an empty slot and create a new card instance
459 		 */
460 		for (i = 0; i < SNDRV_CARDS; i++)
461 			if (enable[i] && ! usb_chip[i] &&
462 			    (vid[i] == -1 || vid[i] == USB_ID_VENDOR(id)) &&
463 			    (pid[i] == -1 || pid[i] == USB_ID_PRODUCT(id))) {
464 				if (snd_usb_audio_create(dev, i, quirk, &chip) < 0) {
465 					goto __error;
466 				}
467 				snd_card_set_dev(chip->card, &intf->dev);
468 				break;
469 			}
470 		if (!chip) {
471 			printk(KERN_ERR "no available usb audio device\n");
472 			goto __error;
473 		}
474 	}
475 
476 	chip->txfr_quirk = 0;
477 	err = 1; /* continue */
478 	if (quirk && quirk->ifnum != QUIRK_NO_INTERFACE) {
479 		/* need some special handlings */
480 		if ((err = snd_usb_create_quirk(chip, intf, &usb_audio_driver, quirk)) < 0)
481 			goto __error;
482 	}
483 
484 	/*
485 	 * For devices with more than one control interface, we assume the
486 	 * first contains the audio controls. We might need a more specific
487 	 * check here in the future.
488 	 */
489 	if (!chip->ctrl_intf)
490 		chip->ctrl_intf = alts;
491 
492 	if (err > 0) {
493 		/* create normal USB audio interfaces */
494 		if (snd_usb_create_streams(chip, ifnum) < 0 ||
495 		    snd_usb_create_mixer(chip, ifnum, ignore_ctl_error) < 0) {
496 			goto __error;
497 		}
498 	}
499 
500 	/* we are allowed to call snd_card_register() many times */
501 	if (snd_card_register(chip->card) < 0) {
502 		goto __error;
503 	}
504 
505 	usb_chip[chip->index] = chip;
506 	chip->num_interfaces++;
507 	mutex_unlock(&register_mutex);
508 	return chip;
509 
510  __error:
511 	if (chip && !chip->num_interfaces)
512 		snd_card_free(chip->card);
513 	mutex_unlock(&register_mutex);
514  __err_val:
515 	return NULL;
516 }
517 
518 /*
519  * we need to take care of counter, since disconnection can be called also
520  * many times as well as usb_audio_probe().
521  */
522 static void snd_usb_audio_disconnect(struct usb_device *dev, void *ptr)
523 {
524 	struct snd_usb_audio *chip;
525 	struct snd_card *card;
526 	struct list_head *p;
527 
528 	if (ptr == (void *)-1L)
529 		return;
530 
531 	chip = ptr;
532 	card = chip->card;
533 	mutex_lock(&register_mutex);
534 	chip->shutdown = 1;
535 	chip->num_interfaces--;
536 	if (chip->num_interfaces <= 0) {
537 		snd_card_disconnect(card);
538 		/* release the pcm resources */
539 		list_for_each(p, &chip->pcm_list) {
540 			snd_usb_stream_disconnect(p);
541 		}
542 		/* release the midi resources */
543 		list_for_each(p, &chip->midi_list) {
544 			snd_usbmidi_disconnect(p);
545 		}
546 		/* release mixer resources */
547 		list_for_each(p, &chip->mixer_list) {
548 			snd_usb_mixer_disconnect(p);
549 		}
550 		usb_chip[chip->index] = NULL;
551 		mutex_unlock(&register_mutex);
552 		snd_card_free_when_closed(card);
553 	} else {
554 		mutex_unlock(&register_mutex);
555 	}
556 }
557 
558 /*
559  * new 2.5 USB kernel API
560  */
561 static int usb_audio_probe(struct usb_interface *intf,
562 			   const struct usb_device_id *id)
563 {
564 	void *chip;
565 	chip = snd_usb_audio_probe(interface_to_usbdev(intf), intf, id);
566 	if (chip) {
567 		usb_set_intfdata(intf, chip);
568 		return 0;
569 	} else
570 		return -EIO;
571 }
572 
573 static void usb_audio_disconnect(struct usb_interface *intf)
574 {
575 	snd_usb_audio_disconnect(interface_to_usbdev(intf),
576 				 usb_get_intfdata(intf));
577 }
578 
579 #ifdef CONFIG_PM
580 static int usb_audio_suspend(struct usb_interface *intf, pm_message_t message)
581 {
582 	struct snd_usb_audio *chip = usb_get_intfdata(intf);
583 	struct list_head *p;
584 	struct snd_usb_stream *as;
585 
586 	if (chip == (void *)-1L)
587 		return 0;
588 
589 	snd_power_change_state(chip->card, SNDRV_CTL_POWER_D3hot);
590 	if (!chip->num_suspended_intf++) {
591 		list_for_each(p, &chip->pcm_list) {
592 			as = list_entry(p, struct snd_usb_stream, list);
593 			snd_pcm_suspend_all(as->pcm);
594 		}
595 	}
596 
597 	return 0;
598 }
599 
600 static int usb_audio_resume(struct usb_interface *intf)
601 {
602 	struct snd_usb_audio *chip = usb_get_intfdata(intf);
603 
604 	if (chip == (void *)-1L)
605 		return 0;
606 	if (--chip->num_suspended_intf)
607 		return 0;
608 	/*
609 	 * ALSA leaves material resumption to user space
610 	 * we just notify
611 	 */
612 
613 	snd_power_change_state(chip->card, SNDRV_CTL_POWER_D0);
614 
615 	return 0;
616 }
617 #else
618 #define usb_audio_suspend	NULL
619 #define usb_audio_resume	NULL
620 #endif		/* CONFIG_PM */
621 
622 static struct usb_device_id usb_audio_ids [] = {
623 #include "quirks-table.h"
624     { .match_flags = (USB_DEVICE_ID_MATCH_INT_CLASS | USB_DEVICE_ID_MATCH_INT_SUBCLASS),
625       .bInterfaceClass = USB_CLASS_AUDIO,
626       .bInterfaceSubClass = USB_SUBCLASS_AUDIOCONTROL },
627     { }						/* Terminating entry */
628 };
629 
630 MODULE_DEVICE_TABLE (usb, usb_audio_ids);
631 
632 /*
633  * entry point for linux usb interface
634  */
635 
636 static struct usb_driver usb_audio_driver = {
637 	.name =		"snd-usb-audio",
638 	.probe =	usb_audio_probe,
639 	.disconnect =	usb_audio_disconnect,
640 	.suspend =	usb_audio_suspend,
641 	.resume =	usb_audio_resume,
642 	.id_table =	usb_audio_ids,
643 };
644 
645 static int __init snd_usb_audio_init(void)
646 {
647 	if (nrpacks < 1 || nrpacks > MAX_PACKS) {
648 		printk(KERN_WARNING "invalid nrpacks value.\n");
649 		return -EINVAL;
650 	}
651 	return usb_register(&usb_audio_driver);
652 }
653 
654 static void __exit snd_usb_audio_cleanup(void)
655 {
656 	usb_deregister(&usb_audio_driver);
657 }
658 
659 module_init(snd_usb_audio_init);
660 module_exit(snd_usb_audio_cleanup);
661