[linux.git] / sound / usb / clock.c

/*
 *   Clock domain and sample rate management functions
 *
 *   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
 *
 */

#include <linux/bitops.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/usb.h>
#include <linux/usb/audio.h>
#include <linux/usb/audio-v2.h>

#include <sound/core.h>
#include <sound/info.h>
#include <sound/pcm.h>

#include "usbaudio.h"
#include "card.h"
#include "helper.h"
#include "clock.h"

static struct uac_clock_source_descriptor *
	snd_usb_find_clock_source(struct usb_host_interface *ctrl_iface,
				  int clock_id)
{
	struct uac_clock_source_descriptor *cs = NULL;

	while ((cs = snd_usb_find_csint_desc(ctrl_iface->extra,
					     ctrl_iface->extralen,
					     cs, UAC2_CLOCK_SOURCE))) {
		if (cs->bClockID == clock_id)
			return cs;
	}

	return NULL;
}

static struct uac_clock_selector_descriptor *
	snd_usb_find_clock_selector(struct usb_host_interface *ctrl_iface,
				    int clock_id)
{
	struct uac_clock_selector_descriptor *cs = NULL;

	while ((cs = snd_usb_find_csint_desc(ctrl_iface->extra,
					     ctrl_iface->extralen,
					     cs, UAC2_CLOCK_SELECTOR))) {
		if (cs->bClockID == clock_id)
			return cs;
	}

	return NULL;
}

static struct uac_clock_multiplier_descriptor *
	snd_usb_find_clock_multiplier(struct usb_host_interface *ctrl_iface,
				      int clock_id)
{
	struct uac_clock_multiplier_descriptor *cs = NULL;

	while ((cs = snd_usb_find_csint_desc(ctrl_iface->extra,
					     ctrl_iface->extralen,
					     cs, UAC2_CLOCK_MULTIPLIER))) {
		if (cs->bClockID == clock_id)
			return cs;
	}

	return NULL;
}

static int uac_clock_selector_get_val(struct snd_usb_audio *chip, int selector_id)
{
	unsigned char buf;
	int ret;

	ret = snd_usb_ctl_msg(chip->dev, usb_rcvctrlpipe(chip->dev, 0),
			      UAC2_CS_CUR,
			      USB_RECIP_INTERFACE | USB_TYPE_CLASS | USB_DIR_IN,
			      UAC2_CX_CLOCK_SELECTOR << 8,
			      snd_usb_ctrl_intf(chip) | (selector_id << 8),
			      &buf, sizeof(buf));

	if (ret < 0)
		return ret;

	return buf;
}

static bool uac_clock_source_is_valid(struct snd_usb_audio *chip, int source_id)
{
	int err;
	unsigned char data;
	struct usb_device *dev = chip->dev;
	struct uac_clock_source_descriptor *cs_desc =
		snd_usb_find_clock_source(chip->ctrl_intf, source_id);

	if (!cs_desc)
		return 0;

	/* If a clock source can't tell us whether it's valid, we assume it is */
	if (!uac2_control_is_readable(cs_desc->bmControls, UAC2_CS_CONTROL_CLOCK_VALID))
		return 1;

	err = snd_usb_ctl_msg(dev, usb_rcvctrlpipe(dev, 0), UAC2_CS_CUR,
			      USB_TYPE_CLASS | USB_RECIP_INTERFACE | USB_DIR_IN,
			      UAC2_CS_CONTROL_CLOCK_VALID << 8,
			      snd_usb_ctrl_intf(chip) | (source_id << 8),
			      &data, sizeof(data));

	if (err < 0) {
		snd_printk(KERN_WARNING "%s(): cannot get clock validity for id %d\n",
			   __func__, source_id);
		return 0;
	}

	return !!data;
}

static int __uac_clock_find_source(struct snd_usb_audio *chip,
				   int entity_id, unsigned long *visited)
{
	struct uac_clock_source_descriptor *source;
	struct uac_clock_selector_descriptor *selector;
	struct uac_clock_multiplier_descriptor *multiplier;

	entity_id &= 0xff;

	if (test_and_set_bit(entity_id, visited)) {
		snd_printk(KERN_WARNING
			"%s(): recursive clock topology detected, id %d.\n",
			__func__, entity_id);
		return -EINVAL;
	}

	/* first, see if the ID we're looking for is a clock source already */
	source = snd_usb_find_clock_source(chip->ctrl_intf, entity_id);
	if (source)
		return source->bClockID;

	selector = snd_usb_find_clock_selector(chip->ctrl_intf, entity_id);
	if (selector) {
		int ret;

		/* the entity ID we are looking for is a selector.
		 * find out what it currently selects */
		ret = uac_clock_selector_get_val(chip, selector->bClockID);
		if (ret < 0)
			return ret;

		/* Selector values are one-based */

		if (ret > selector->bNrInPins || ret < 1) {
			printk(KERN_ERR
				"%s(): selector reported illegal value, id %d, ret %d\n",
				__func__, selector->bClockID, ret);

			return -EINVAL;
		}

		return __uac_clock_find_source(chip, selector->baCSourceID[ret-1],
					       visited);
	}

	/* FIXME: multipliers only act as pass-thru element for now */
	multiplier = snd_usb_find_clock_multiplier(chip->ctrl_intf, entity_id);
	if (multiplier)
		return __uac_clock_find_source(chip, multiplier->bCSourceID,
						visited);

	return -EINVAL;
}

/*
 * For all kinds of sample rate settings and other device queries,
 * the clock source (end-leaf) must be used. However, clock selectors,
 * clock multipliers and sample rate converters may be specified as
 * clock source input to terminal. This functions walks the clock path
 * to its end and tries to find the source.
 *
 * The 'visited' bitfield is used internally to detect recursive loops.
 *
 * Returns the clock source UnitID (>=0) on success, or an error.
 */
int snd_usb_clock_find_source(struct snd_usb_audio *chip, int entity_id)
{
	DECLARE_BITMAP(visited, 256);
	memset(visited, 0, sizeof(visited));
	return __uac_clock_find_source(chip, entity_id, visited);
}

static int set_sample_rate_v1(struct snd_usb_audio *chip, int iface,
			      struct usb_host_interface *alts,
			      struct audioformat *fmt, int rate)
{
	struct usb_device *dev = chip->dev;
	unsigned int ep;
	unsigned char data[3];
	int err, crate;

	ep = get_endpoint(alts, 0)->bEndpointAddress;

	/* if endpoint doesn't have sampling rate control, bail out */
	if (!(fmt->attributes & UAC_EP_CS_ATTR_SAMPLE_RATE))
		return 0;

	data[0] = rate;
	data[1] = rate >> 8;
	data[2] = rate >> 16;
	if ((err = snd_usb_ctl_msg(dev, usb_sndctrlpipe(dev, 0), UAC_SET_CUR,
				   USB_TYPE_CLASS | USB_RECIP_ENDPOINT | USB_DIR_OUT,
				   UAC_EP_CS_ATTR_SAMPLE_RATE << 8, ep,
				   data, sizeof(data))) < 0) {
		snd_printk(KERN_ERR "%d:%d:%d: cannot set freq %d to ep %#x\n",
			   dev->devnum, iface, fmt->altsetting, rate, ep);
		return err;
	}

	if ((err = snd_usb_ctl_msg(dev, usb_rcvctrlpipe(dev, 0), UAC_GET_CUR,
				   USB_TYPE_CLASS | USB_RECIP_ENDPOINT | USB_DIR_IN,
				   UAC_EP_CS_ATTR_SAMPLE_RATE << 8, ep,
				   data, sizeof(data))) < 0) {
		snd_printk(KERN_WARNING "%d:%d:%d: cannot get freq at ep %#x\n",
			   dev->devnum, iface, fmt->altsetting, ep);
		return 0; /* some devices don't support reading */
	}

	crate = data[0] | (data[1] << 8) | (data[2] << 16);
	if (crate != rate) {
		snd_printd(KERN_WARNING "current rate %d is different from the runtime rate %d\n", crate, rate);
		// runtime->rate = crate;
	}

	return 0;
}

static int set_sample_rate_v2(struct snd_usb_audio *chip, int iface,
			      struct usb_host_interface *alts,
			      struct audioformat *fmt, int rate)
{
	struct usb_device *dev = chip->dev;
	unsigned char data[4];
	int err, crate;
	int clock = snd_usb_clock_find_source(chip, fmt->clock);

	if (clock < 0)
		return clock;

	if (!uac_clock_source_is_valid(chip, clock)) {
		/* TODO: should we try to find valid clock setups by ourself? */
		snd_printk(KERN_ERR "%d:%d:%d: clock source %d is not valid, cannot use\n",
			   dev->devnum, iface, fmt->altsetting, clock);
		return -ENXIO;
	}

	data[0] = rate;
	data[1] = rate >> 8;
	data[2] = rate >> 16;
	data[3] = rate >> 24;
	if ((err = snd_usb_ctl_msg(dev, usb_sndctrlpipe(dev, 0), UAC2_CS_CUR,
				   USB_TYPE_CLASS | USB_RECIP_INTERFACE | USB_DIR_OUT,
				   UAC2_CS_CONTROL_SAM_FREQ << 8,
				   snd_usb_ctrl_intf(chip) | (clock << 8),
				   data, sizeof(data))) < 0) {
		snd_printk(KERN_ERR "%d:%d:%d: cannot set freq %d (v2)\n",
			   dev->devnum, iface, fmt->altsetting, rate);
		return err;
	}

	if ((err = snd_usb_ctl_msg(dev, usb_rcvctrlpipe(dev, 0), UAC2_CS_CUR,
				   USB_TYPE_CLASS | USB_RECIP_INTERFACE | USB_DIR_IN,
				   UAC2_CS_CONTROL_SAM_FREQ << 8,
				   snd_usb_ctrl_intf(chip) | (clock << 8),
				   data, sizeof(data))) < 0) {
		snd_printk(KERN_WARNING "%d:%d:%d: cannot get freq (v2)\n",
			   dev->devnum, iface, fmt->altsetting);
		return err;
	}

	crate = data[0] | (data[1] << 8) | (data[2] << 16) | (data[3] << 24);
	if (crate != rate)
		snd_printd(KERN_WARNING "current rate %d is different from the runtime rate %d\n", crate, rate);

	return 0;
}

int snd_usb_init_sample_rate(struct snd_usb_audio *chip, int iface,
			     struct usb_host_interface *alts,
			     struct audioformat *fmt, int rate)
{
	struct usb_interface_descriptor *altsd = get_iface_desc(alts);

	switch (altsd->bInterfaceProtocol) {
	case UAC_VERSION_1:
	default:
		return set_sample_rate_v1(chip, iface, alts, fmt, rate);

	case UAC_VERSION_2:
		return set_sample_rate_v2(chip, iface, alts, fmt, rate);
	}
}
Commit	Line	Data
79f920fb DM	1	/*
	2	* Clock domain and sample rate management functions
	3	*
	4	* This program is free software; you can redistribute it and/or modify
	5	* it under the terms of the GNU General Public License as published by
	6	* the Free Software Foundation; either version 2 of the License, or
	7	* (at your option) any later version.
	8	*
	9	* This program is distributed in the hope that it will be useful,
	10	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	11	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	12	* GNU General Public License for more details.
	13	*
	14	* You should have received a copy of the GNU General Public License
	15	* along with this program; if not, write to the Free Software
	16	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
	17	*
	18	*/
	19
	20	#include <linux/bitops.h>
	21	#include <linux/init.h>
79f920fb DM	22	#include <linux/string.h>
79f920fb DM	23	#include <linux/usb.h>
79f920fb DM	24	#include <linux/usb/audio.h>
	25	#include <linux/usb/audio-v2.h>
	26
	27	#include <sound/core.h>
	28	#include <sound/info.h>
	29	#include <sound/pcm.h>
79f920fb DM	30
	31	#include "usbaudio.h"
	32	#include "card.h"
79f920fb	33	#include "helper.h"
f22aa949	34	#include "clock.h"
79f920fb DM	35
	36	static struct uac_clock_source_descriptor *
	37	snd_usb_find_clock_source(struct usb_host_interface *ctrl_iface,
	38	int clock_id)
	39	{
	40	struct uac_clock_source_descriptor *cs = NULL;
	41
	42	while ((cs = snd_usb_find_csint_desc(ctrl_iface->extra,
	43	ctrl_iface->extralen,
	44	cs, UAC2_CLOCK_SOURCE))) {
	45	if (cs->bClockID == clock_id)
	46	return cs;
	47	}
	48
	49	return NULL;
	50	}
	51
	52	static struct uac_clock_selector_descriptor *
	53	snd_usb_find_clock_selector(struct usb_host_interface *ctrl_iface,
	54	int clock_id)
	55	{
	56	struct uac_clock_selector_descriptor *cs = NULL;
	57
	58	while ((cs = snd_usb_find_csint_desc(ctrl_iface->extra,
	59	ctrl_iface->extralen,
	60	cs, UAC2_CLOCK_SELECTOR))) {
	61	if (cs->bClockID == clock_id)
	62	return cs;
	63	}
	64
	65	return NULL;
	66	}
	67
	68	static struct uac_clock_multiplier_descriptor *
	69	snd_usb_find_clock_multiplier(struct usb_host_interface *ctrl_iface,
	70	int clock_id)
	71	{
	72	struct uac_clock_multiplier_descriptor *cs = NULL;
	73
	74	while ((cs = snd_usb_find_csint_desc(ctrl_iface->extra,
	75	ctrl_iface->extralen,
	76	cs, UAC2_CLOCK_MULTIPLIER))) {
	77	if (cs->bClockID == clock_id)
	78	return cs;
	79	}
	80
	81	return NULL;
	82	}
	83
	84	static int uac_clock_selector_get_val(struct snd_usb_audio *chip, int selector_id)
	85	{
	86	unsigned char buf;
	87	int ret;
	88
	89	ret = snd_usb_ctl_msg(chip->dev, usb_rcvctrlpipe(chip->dev, 0),
	90	UAC2_CS_CUR,
	91	USB_RECIP_INTERFACE \| USB_TYPE_CLASS \| USB_DIR_IN,
11bcbc44 DM	92	UAC2_CX_CLOCK_SELECTOR << 8,
11bcbc44 DM	93	snd_usb_ctrl_intf(chip) \| (selector_id << 8),
17d900c4	94	&buf, sizeof(buf));
79f920fb DM	95
	96	if (ret < 0)
	97	return ret;
	98
	99	return buf;
	100	}
	101
	102	static bool uac_clock_source_is_valid(struct snd_usb_audio *chip, int source_id)
	103	{
	104	int err;
	105	unsigned char data;
	106	struct usb_device *dev = chip->dev;
3bc6fbc7 DM	107	struct uac_clock_source_descriptor *cs_desc =
	108	snd_usb_find_clock_source(chip->ctrl_intf, source_id);
	109
	110	if (!cs_desc)
	111	return 0;
	112
	113	/* If a clock source can't tell us whether it's valid, we assume it is */
	114	if (!uac2_control_is_readable(cs_desc->bmControls, UAC2_CS_CONTROL_CLOCK_VALID))
	115	return 1;
79f920fb DM	116
	117	err = snd_usb_ctl_msg(dev, usb_rcvctrlpipe(dev, 0), UAC2_CS_CUR,
	118	USB_TYPE_CLASS \| USB_RECIP_INTERFACE \| USB_DIR_IN,
11bcbc44 DM	119	UAC2_CS_CONTROL_CLOCK_VALID << 8,
11bcbc44 DM	120	snd_usb_ctrl_intf(chip) \| (source_id << 8),
17d900c4	121	&data, sizeof(data));
79f920fb DM	122
	123	if (err < 0) {
	124	snd_printk(KERN_WARNING "%s(): cannot get clock validity for id %d\n",
	125	__func__, source_id);
3bc6fbc7	126	return 0;
79f920fb DM	127	}
	128
	129	return !!data;
	130	}
	131
79f920fb	132	static int __uac_clock_find_source(struct snd_usb_audio *chip,
79f920fb DM	133	int entity_id, unsigned long *visited)
	134	{
	135	struct uac_clock_source_descriptor *source;
	136	struct uac_clock_selector_descriptor *selector;
	137	struct uac_clock_multiplier_descriptor *multiplier;
	138
	139	entity_id &= 0xff;
	140
	141	if (test_and_set_bit(entity_id, visited)) {
	142	snd_printk(KERN_WARNING
	143	"%s(): recursive clock topology detected, id %d.\n",
	144	__func__, entity_id);
	145	return -EINVAL;
	146	}
	147
	148	/* first, see if the ID we're looking for is a clock source already */
3d8d4dcf	149	source = snd_usb_find_clock_source(chip->ctrl_intf, entity_id);
79f920fb DM	150	if (source)
	151	return source->bClockID;
	152
3d8d4dcf	153	selector = snd_usb_find_clock_selector(chip->ctrl_intf, entity_id);
79f920fb DM	154	if (selector) {
	155	int ret;
	156
	157	/* the entity ID we are looking for is a selector.
	158	* find out what it currently selects */
	159	ret = uac_clock_selector_get_val(chip, selector->bClockID);
	160	if (ret < 0)
	161	return ret;
	162
157a57b6 DM	163	/* Selector values are one-based */
157a57b6 DM	164
79f920fb DM	165	if (ret > selector->bNrInPins \|\| ret < 1) {
	166	printk(KERN_ERR
	167	"%s(): selector reported illegal value, id %d, ret %d\n",
	168	__func__, selector->bClockID, ret);
	169
	170	return -EINVAL;
	171	}
	172
3d8d4dcf	173	return __uac_clock_find_source(chip, selector->baCSourceID[ret-1],
79f920fb DM	174	visited);
	175	}
	176
	177	/* FIXME: multipliers only act as pass-thru element for now */
3d8d4dcf	178	multiplier = snd_usb_find_clock_multiplier(chip->ctrl_intf, entity_id);
79f920fb	179	if (multiplier)
3d8d4dcf DM	180	return __uac_clock_find_source(chip, multiplier->bCSourceID,
3d8d4dcf DM	181	visited);
79f920fb DM	182
	183	return -EINVAL;
	184	}
	185
157a57b6 DM	186	/*
	187	* For all kinds of sample rate settings and other device queries,
	188	* the clock source (end-leaf) must be used. However, clock selectors,
	189	* clock multipliers and sample rate converters may be specified as
	190	* clock source input to terminal. This functions walks the clock path
	191	* to its end and tries to find the source.
	192	*
	193	* The 'visited' bitfield is used internally to detect recursive loops.
	194	*
	195	* Returns the clock source UnitID (>=0) on success, or an error.
	196	*/
3d8d4dcf	197	int snd_usb_clock_find_source(struct snd_usb_audio *chip, int entity_id)
79f920fb DM	198	{
	199	DECLARE_BITMAP(visited, 256);
	200	memset(visited, 0, sizeof(visited));
3d8d4dcf	201	return __uac_clock_find_source(chip, entity_id, visited);
79f920fb DM	202	}
	203
	204	static int set_sample_rate_v1(struct snd_usb_audio *chip, int iface,
	205	struct usb_host_interface *alts,
	206	struct audioformat *fmt, int rate)
	207	{
	208	struct usb_device *dev = chip->dev;
	209	unsigned int ep;
	210	unsigned char data[3];
	211	int err, crate;
	212
	213	ep = get_endpoint(alts, 0)->bEndpointAddress;
	214
	215	/* if endpoint doesn't have sampling rate control, bail out */
d32d552e	216	if (!(fmt->attributes & UAC_EP_CS_ATTR_SAMPLE_RATE))
79f920fb	217	return 0;
79f920fb DM	218
	219	data[0] = rate;
	220	data[1] = rate >> 8;
	221	data[2] = rate >> 16;
	222	if ((err = snd_usb_ctl_msg(dev, usb_sndctrlpipe(dev, 0), UAC_SET_CUR,
	223	USB_TYPE_CLASS \| USB_RECIP_ENDPOINT \| USB_DIR_OUT,
	224	UAC_EP_CS_ATTR_SAMPLE_RATE << 8, ep,
17d900c4	225	data, sizeof(data))) < 0) {
79f920fb DM	226	snd_printk(KERN_ERR "%d:%d:%d: cannot set freq %d to ep %#x\n",
	227	dev->devnum, iface, fmt->altsetting, rate, ep);
	228	return err;
	229	}
	230
	231	if ((err = snd_usb_ctl_msg(dev, usb_rcvctrlpipe(dev, 0), UAC_GET_CUR,
	232	USB_TYPE_CLASS \| USB_RECIP_ENDPOINT \| USB_DIR_IN,
	233	UAC_EP_CS_ATTR_SAMPLE_RATE << 8, ep,
17d900c4	234	data, sizeof(data))) < 0) {
79f920fb DM	235	snd_printk(KERN_WARNING "%d:%d:%d: cannot get freq at ep %#x\n",
	236	dev->devnum, iface, fmt->altsetting, ep);
	237	return 0; /* some devices don't support reading */
	238	}
	239
	240	crate = data[0] \| (data[1] << 8) \| (data[2] << 16);
	241	if (crate != rate) {
	242	snd_printd(KERN_WARNING "current rate %d is different from the runtime rate %d\n", crate, rate);
	243	// runtime->rate = crate;
	244	}
	245
	246	return 0;
	247	}
	248
	249	static int set_sample_rate_v2(struct snd_usb_audio *chip, int iface,
	250	struct usb_host_interface *alts,
	251	struct audioformat *fmt, int rate)
	252	{
	253	struct usb_device *dev = chip->dev;
	254	unsigned char data[4];
	255	int err, crate;
3d8d4dcf	256	int clock = snd_usb_clock_find_source(chip, fmt->clock);
79f920fb DM	257
	258	if (clock < 0)
	259	return clock;
	260
	261	if (!uac_clock_source_is_valid(chip, clock)) {
157a57b6	262	/* TODO: should we try to find valid clock setups by ourself? */
79f920fb DM	263	snd_printk(KERN_ERR "%d:%d:%d: clock source %d is not valid, cannot use\n",
	264	dev->devnum, iface, fmt->altsetting, clock);
	265	return -ENXIO;
	266	}
	267
	268	data[0] = rate;
	269	data[1] = rate >> 8;
	270	data[2] = rate >> 16;
	271	data[3] = rate >> 24;
	272	if ((err = snd_usb_ctl_msg(dev, usb_sndctrlpipe(dev, 0), UAC2_CS_CUR,
	273	USB_TYPE_CLASS \| USB_RECIP_INTERFACE \| USB_DIR_OUT,
11bcbc44 DM	274	UAC2_CS_CONTROL_SAM_FREQ << 8,
11bcbc44 DM	275	snd_usb_ctrl_intf(chip) \| (clock << 8),
17d900c4	276	data, sizeof(data))) < 0) {
79f920fb DM	277	snd_printk(KERN_ERR "%d:%d:%d: cannot set freq %d (v2)\n",
	278	dev->devnum, iface, fmt->altsetting, rate);
	279	return err;
	280	}
	281
	282	if ((err = snd_usb_ctl_msg(dev, usb_rcvctrlpipe(dev, 0), UAC2_CS_CUR,
	283	USB_TYPE_CLASS \| USB_RECIP_INTERFACE \| USB_DIR_IN,
11bcbc44 DM	284	UAC2_CS_CONTROL_SAM_FREQ << 8,
11bcbc44 DM	285	snd_usb_ctrl_intf(chip) \| (clock << 8),
17d900c4	286	data, sizeof(data))) < 0) {
79f920fb DM	287	snd_printk(KERN_WARNING "%d:%d:%d: cannot get freq (v2)\n",
	288	dev->devnum, iface, fmt->altsetting);
	289	return err;
	290	}
	291
	292	crate = data[0] \| (data[1] << 8) \| (data[2] << 16) \| (data[3] << 24);
	293	if (crate != rate)
	294	snd_printd(KERN_WARNING "current rate %d is different from the runtime rate %d\n", crate, rate);
	295
	296	return 0;
	297	}
	298
	299	int snd_usb_init_sample_rate(struct snd_usb_audio *chip, int iface,
	300	struct usb_host_interface *alts,
	301	struct audioformat *fmt, int rate)
	302	{
	303	struct usb_interface_descriptor *altsd = get_iface_desc(alts);
	304
	305	switch (altsd->bInterfaceProtocol) {
	306	case UAC_VERSION_1:
a2acad82	307	default:
79f920fb DM	308	return set_sample_rate_v1(chip, iface, alts, fmt, rate);
	309
	310	case UAC_VERSION_2:
	311	return set_sample_rate_v2(chip, iface, alts, fmt, rate);
	312	}
79f920fb DM	313	}
79f920fb DM	314