sound/usb/clock.c - kernel/msm-4.9 - Gitiles

 /*
  *   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"
 #include "quirks.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 int uac_clock_selector_set_val(struct snd_usb_audio *chip, int selector_id,
 					unsigned char pin)
 {
 	int ret;

 	ret = snd_usb_ctl_msg(chip->dev, usb_sndctrlpipe(chip->dev, 0),
 			      UAC2_CS_CUR,
 			      USB_RECIP_INTERFACE | USB_TYPE_CLASS | USB_DIR_OUT,
 			      UAC2_CX_CLOCK_SELECTOR << 8,
 			      snd_usb_ctrl_intf(chip) | (selector_id << 8),
 			      &pin, sizeof(pin));
 	if (ret < 0)
 		return ret;

 	if (ret != sizeof(pin)) {
 		snd_printk(KERN_ERR
 			"usb-audio:%d: setting selector (id %d) unexpected length %d\n",
 			chip->dev->devnum, selector_id, ret);
 		return -EINVAL;
 	}

 	ret = uac_clock_selector_get_val(chip, selector_id);
 	if (ret < 0)
 		return ret;

 	if (ret != pin) {
 		snd_printk(KERN_ERR
 			"usb-audio:%d: setting selector (id %d) to %x failed (current: %d)\n",
 			chip->dev->devnum, selector_id, pin, ret);
 		return -EINVAL;
 	}

 	return ret;
 }

 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 - 1))
 		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,
 				   bool validate)
 {
 	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) {
 		entity_id = source->bClockID;
 		if (validate && !uac_clock_source_is_valid(chip, entity_id)) {
 			snd_printk(KERN_ERR "usb-audio:%d: clock source %d is not valid, cannot use\n",
 				   chip->dev->devnum, entity_id);
 			return -ENXIO;
 		}
 		return entity_id;
 	}

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

 		/* 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) {
 			snd_printk(KERN_ERR
 				"%s(): selector reported illegal value, id %d, ret %d\n",
 				__func__, selector->bClockID, ret);

 			return -EINVAL;
 		}

 		cur = ret;
 		ret = __uac_clock_find_source(chip, selector->baCSourceID[ret - 1],
 					       visited, validate);
 		if (!validate || ret > 0 || !chip->autoclock)
 			return ret;

 		/* The current clock source is invalid, try others. */
 		for (i = 1; i <= selector->bNrInPins; i++) {
 			int err;

 			if (i == cur)
 				continue;

 			ret = __uac_clock_find_source(chip, selector->baCSourceID[i - 1],
 				visited, true);
 			if (ret < 0)
 				continue;

 			err = uac_clock_selector_set_val(chip, entity_id, i);
 			if (err < 0)
 				continue;

 			snd_printk(KERN_INFO
 				"usb-audio:%d: found and selected valid clock source %d\n",
 				chip->dev->devnum, ret);
 			return ret;
 		}

 		return -ENXIO;
 	}

 	/* 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, validate);

 	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,
 			      bool validate)
 {
 	DECLARE_BITMAP(visited, 256);
 	memset(visited, 0, sizeof(visited));
 	return __uac_clock_find_source(chip, entity_id, visited, validate);
 }

 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 get_sample_rate_v2(struct snd_usb_audio *chip, int iface,
 			      int altsetting, int clock)
 {
 	struct usb_device *dev = chip->dev;
 	__le32 data;
 	int err;

 	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));
 	if (err < 0) {
 		snd_printk(KERN_WARNING "%d:%d:%d: cannot get freq (v2): err %d\n",
 			   dev->devnum, iface, altsetting, err);
 		return 0;
 	}

 	return le32_to_cpu(data);
 }

 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;
 	__le32 data;
 	int err, cur_rate, prev_rate;
 	int clock;
 	bool writeable;
 	struct uac_clock_source_descriptor *cs_desc;

 	clock = snd_usb_clock_find_source(chip, fmt->clock, true);
 	if (clock < 0)
 		return clock;

 	prev_rate = get_sample_rate_v2(chip, iface, fmt->altsetting, clock);
 	if (prev_rate == rate)
 		return 0;

 	cs_desc = snd_usb_find_clock_source(chip->ctrl_intf, clock);
 	writeable = uac2_control_is_writeable(cs_desc->bmControls, UAC2_CS_CONTROL_SAM_FREQ - 1);
 	if (writeable) {
 		data = cpu_to_le32(rate);
 		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));
 		if (err < 0) {
 			snd_printk(KERN_ERR "%d:%d:%d: cannot set freq %d (v2): err %d\n",
 				   dev->devnum, iface, fmt->altsetting, rate, err);
 			return err;
 		}

 		cur_rate = get_sample_rate_v2(chip, iface, fmt->altsetting, clock);
 	} else {
 		cur_rate = prev_rate;
 	}

 	if (cur_rate != rate) {
 		if (!writeable) {
 			snd_printk(KERN_WARNING
 				   "%d:%d:%d: freq mismatch (RO clock): req %d, clock runs @%d\n",
 				   dev->devnum, iface, fmt->altsetting, rate, cur_rate);
 			return -ENXIO;
 		}
 		snd_printd(KERN_WARNING
 			   "current rate %d is different from the runtime rate %d\n",
 			   cur_rate, rate);
 	}

 	/* Some devices doesn't respond to sample rate changes while the
 	 * interface is active. */
 	if (rate != prev_rate) {
 		usb_set_interface(dev, iface, 0);
 		snd_usb_set_interface_quirk(dev);
 		usb_set_interface(dev, iface, fmt->altsetting);
 		snd_usb_set_interface_quirk(dev);
 	}

 	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);
 	}
 }
	/*
	* 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"
	#include "quirks.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 int uac_clock_selector_set_val(struct snd_usb_audio *chip, int selector_id,
	unsigned char pin)
	{
	int ret;

	ret = snd_usb_ctl_msg(chip->dev, usb_sndctrlpipe(chip->dev, 0),
	UAC2_CS_CUR,
	USB_RECIP_INTERFACE \| USB_TYPE_CLASS \| USB_DIR_OUT,
	UAC2_CX_CLOCK_SELECTOR << 8,
	snd_usb_ctrl_intf(chip) \| (selector_id << 8),
	&pin, sizeof(pin));
	if (ret < 0)
	return ret;

	if (ret != sizeof(pin)) {
	snd_printk(KERN_ERR
	"usb-audio:%d: setting selector (id %d) unexpected length %d\n",
	chip->dev->devnum, selector_id, ret);
	return -EINVAL;
	}

	ret = uac_clock_selector_get_val(chip, selector_id);
	if (ret < 0)
	return ret;

	if (ret != pin) {
	snd_printk(KERN_ERR
	"usb-audio:%d: setting selector (id %d) to %x failed (current: %d)\n",
	chip->dev->devnum, selector_id, pin, ret);
	return -EINVAL;
	}

	return ret;
	}

	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 - 1))
	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,
	bool validate)
	{
	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) {
	entity_id = source->bClockID;
	if (validate && !uac_clock_source_is_valid(chip, entity_id)) {
	snd_printk(KERN_ERR "usb-audio:%d: clock source %d is not valid, cannot use\n",
	chip->dev->devnum, entity_id);
	return -ENXIO;
	}
	return entity_id;
	}

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

	/* 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) {
	snd_printk(KERN_ERR
	"%s(): selector reported illegal value, id %d, ret %d\n",
	__func__, selector->bClockID, ret);

	return -EINVAL;
	}

	cur = ret;
	ret = __uac_clock_find_source(chip, selector->baCSourceID[ret - 1],
	visited, validate);
	if (!validate \|\| ret > 0 \|\| !chip->autoclock)
	return ret;

	/* The current clock source is invalid, try others. */
	for (i = 1; i <= selector->bNrInPins; i++) {
	int err;

	if (i == cur)
	continue;

	ret = __uac_clock_find_source(chip, selector->baCSourceID[i - 1],
	visited, true);
	if (ret < 0)
	continue;

	err = uac_clock_selector_set_val(chip, entity_id, i);
	if (err < 0)
	continue;

	snd_printk(KERN_INFO
	"usb-audio:%d: found and selected valid clock source %d\n",
	chip->dev->devnum, ret);
	return ret;
	}

	return -ENXIO;
	}

	/* 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, validate);

	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,
	bool validate)
	{
	DECLARE_BITMAP(visited, 256);
	memset(visited, 0, sizeof(visited));
	return __uac_clock_find_source(chip, entity_id, visited, validate);
	}

	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 get_sample_rate_v2(struct snd_usb_audio *chip, int iface,
	int altsetting, int clock)
	{
	struct usb_device *dev = chip->dev;
	__le32 data;
	int err;

	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));
	if (err < 0) {
	snd_printk(KERN_WARNING "%d:%d:%d: cannot get freq (v2): err %d\n",
	dev->devnum, iface, altsetting, err);
	return 0;
	}

	return le32_to_cpu(data);
	}

	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;
	__le32 data;
	int err, cur_rate, prev_rate;
	int clock;
	bool writeable;
	struct uac_clock_source_descriptor *cs_desc;

	clock = snd_usb_clock_find_source(chip, fmt->clock, true);
	if (clock < 0)
	return clock;

	prev_rate = get_sample_rate_v2(chip, iface, fmt->altsetting, clock);
	if (prev_rate == rate)
	return 0;

	cs_desc = snd_usb_find_clock_source(chip->ctrl_intf, clock);
	writeable = uac2_control_is_writeable(cs_desc->bmControls, UAC2_CS_CONTROL_SAM_FREQ - 1);
	if (writeable) {
	data = cpu_to_le32(rate);
	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));
	if (err < 0) {
	snd_printk(KERN_ERR "%d:%d:%d: cannot set freq %d (v2): err %d\n",
	dev->devnum, iface, fmt->altsetting, rate, err);
	return err;
	}

	cur_rate = get_sample_rate_v2(chip, iface, fmt->altsetting, clock);
	} else {
	cur_rate = prev_rate;
	}

	if (cur_rate != rate) {
	if (!writeable) {
	snd_printk(KERN_WARNING
	"%d:%d:%d: freq mismatch (RO clock): req %d, clock runs @%d\n",
	dev->devnum, iface, fmt->altsetting, rate, cur_rate);
	return -ENXIO;
	}
	snd_printd(KERN_WARNING
	"current rate %d is different from the runtime rate %d\n",
	cur_rate, rate);
	}

	/* Some devices doesn't respond to sample rate changes while the
	* interface is active. */
	if (rate != prev_rate) {
	usb_set_interface(dev, iface, 0);
	snd_usb_set_interface_quirk(dev);
	usb_set_interface(dev, iface, fmt->altsetting);
	snd_usb_set_interface_quirk(dev);
	}

	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);
	}
	}