endpoint.o \
                        urb.o \
                        pcm.o \
-                       helper.o
+                       helper.o \
+                       clock.o
 
 snd-usbmidi-lib-objs := midi.o
 
 
        }
 
        case UAC_VERSION_2: {
-               struct uac_clock_source_descriptor *cs;
                struct usb_interface_assoc_descriptor *assoc =
                        usb_ifnum_to_if(dev, ctrlif)->intf_assoc;
 
                        return -EINVAL;
                }
 
-               /* FIXME: for now, we expect there is at least one clock source
-                * descriptor and we always take the first one.
-                * We should properly support devices with multiple clock sources,
-                * clock selectors and sample rate conversion units. */
-
-               cs = snd_usb_find_csint_desc(host_iface->extra, host_iface->extralen,
-                                               NULL, UAC2_CLOCK_SOURCE);
-
-               if (!cs) {
-                       snd_printk(KERN_ERR "CLOCK_SOURCE descriptor not found\n");
-                       return -EINVAL;
-               }
-
-               chip->clock_id = cs->bClockID;
-
                for (i = 0; i < assoc->bInterfaceCount; i++) {
                        int intf = assoc->bFirstInterface + i;
 
                        goto __error;
        }
 
+       chip->ctrl_intf = alts;
+
        if (err > 0) {
                /* create normal USB audio interfaces */
                if (snd_usb_create_streams(chip, ifnum) < 0 ||
 
        unsigned int rate_min, rate_max;        /* min/max rates */
        unsigned int nr_rates;          /* number of rate table entries */
        unsigned int *rate_table;       /* rate table */
+       unsigned char clock;            /* associated clock */
 };
 
 struct snd_usb_substream;
 
--- /dev/null
+/*
+ *   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/list.h>
+#include <linux/slab.h>
+#include <linux/string.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 <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 "urb.h"
+#include "format.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, selector_id << 8,
+                             &buf, sizeof(buf), 1000);
+
+       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;
+
+       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, source_id << 8,
+                             &data, sizeof(data), 1000);
+
+       if (err < 0) {
+               snd_printk(KERN_WARNING "%s(): cannot get clock validity for id %d\n",
+                          __func__, source_id);
+               return err;
+       }
+
+       return !!data;
+}
+
+/* Try to find the clock source ID of a given clock entity */
+
+static int __uac_clock_find_source(struct snd_usb_audio *chip,
+                                  struct usb_host_interface *host_iface,
+                                  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(host_iface, entity_id);
+       if (source)
+               return source->bClockID;
+
+       selector = snd_usb_find_clock_selector(host_iface, 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;
+
+               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, host_iface,
+                                              selector->baCSourceID[ret-1],
+                                              visited);
+       }
+
+       /* FIXME: multipliers only act as pass-thru element for now */
+       multiplier = snd_usb_find_clock_multiplier(host_iface, entity_id);
+       if (multiplier)
+               return __uac_clock_find_source(chip, host_iface,
+                                              multiplier->bCSourceID, visited);
+
+       return -EINVAL;
+}
+
+int snd_usb_clock_find_source(struct snd_usb_audio *chip,
+                             struct usb_host_interface *host_iface,
+                             int entity_id)
+{
+       DECLARE_BITMAP(visited, 256);
+       memset(visited, 0, sizeof(visited));
+       return __uac_clock_find_source(chip, host_iface, 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)) {
+               snd_printk(KERN_WARNING "%d:%d:%d: endpoint lacks sample rate attribute bit, cannot set.\n",
+                                  dev->devnum, iface, fmt->altsetting);
+               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), 1000)) < 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), 1000)) < 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, chip->ctrl_intf, fmt->clock);
+
+       if (clock < 0)
+               return clock;
+
+       if (!uac_clock_source_is_valid(chip, clock)) {
+               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, clock << 8,
+                                  data, sizeof(data), 1000)) < 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, clock << 8,
+                                  data, sizeof(data), 1000)) < 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:
+               return set_sample_rate_v1(chip, iface, alts, fmt, rate);
+
+       case UAC_VERSION_2:
+               return set_sample_rate_v2(chip, iface, alts, fmt, rate);
+       }
+
+       return -EINVAL;
+}
+
 
--- /dev/null
+#ifndef __USBAUDIO_CLOCK_H
+#define __USBAUDIO_CLOCK_H
+
+int snd_usb_init_sample_rate(struct snd_usb_audio *chip, int iface,
+                            struct usb_host_interface *alts,
+                            struct audioformat *fmt, int rate);
+
+int snd_usb_clock_find_source(struct snd_usb_audio *chip,
+                             struct usb_host_interface *host_iface,
+                             int entity_id);
+
+#endif /* __USBAUDIO_CLOCK_H */
 
        return attributes;
 }
 
+static struct uac2_input_terminal_descriptor *
+       snd_usb_find_input_terminal_descriptor(struct usb_host_interface *ctrl_iface,
+                                              int terminal_id)
+{
+       struct uac2_input_terminal_descriptor *term = NULL;
+
+       while ((term = snd_usb_find_csint_desc(ctrl_iface->extra,
+                                              ctrl_iface->extralen,
+                                              term, UAC_INPUT_TERMINAL))) {
+               if (term->bTerminalID == terminal_id)
+                       return term;
+       }
+
+       return NULL;
+}
+
+static struct uac2_output_terminal_descriptor *
+       snd_usb_find_output_terminal_descriptor(struct usb_host_interface *ctrl_iface,
+                                               int terminal_id)
+{
+       struct uac2_output_terminal_descriptor *term = NULL;
+
+       while ((term = snd_usb_find_csint_desc(ctrl_iface->extra,
+                                              ctrl_iface->extralen,
+                                              term, UAC_OUTPUT_TERMINAL))) {
+               if (term->bTerminalID == terminal_id)
+                       return term;
+       }
+
+       return NULL;
+}
+
 int snd_usb_parse_audio_endpoints(struct snd_usb_audio *chip, int iface_no)
 {
        struct usb_device *dev;
        int i, altno, err, stream;
        int format = 0, num_channels = 0;
        struct audioformat *fp = NULL;
-       int num, protocol;
+       int num, protocol, clock = 0;
        struct uac_format_type_i_continuous_descriptor *fmt;
 
        dev = chip->dev;
                }
 
                case UAC_VERSION_2: {
+                       struct uac2_input_terminal_descriptor *input_term;
+                       struct uac2_output_terminal_descriptor *output_term;
                        struct uac_as_header_descriptor_v2 *as =
                                snd_usb_find_csint_desc(alts->extra, alts->extralen, NULL, UAC_AS_GENERAL);
 
                        num_channels = as->bNrChannels;
                        format = le32_to_cpu(as->bmFormats);
 
-                       break;
+                       /* lookup the terminal associated to this interface
+                        * to extract the clock */
+                       input_term = snd_usb_find_input_terminal_descriptor(chip->ctrl_intf,
+                                                                           as->bTerminalLink);
+                       if (input_term) {
+                               clock = input_term->bCSourceID;
+                               break;
+                       }
+
+                       output_term = snd_usb_find_output_terminal_descriptor(chip->ctrl_intf,
+                                                                             as->bTerminalLink);
+                       if (output_term) {
+                               clock = output_term->bCSourceID;
+                               break;
+                       }
+
+                       snd_printk(KERN_ERR "%d:%u:%d : bogus bTerminalLink %d\n",
+                                  dev->devnum, iface_no, altno, as->bTerminalLink);
+                       continue;
                }
 
                default:
                        fp->maxpacksize = (((fp->maxpacksize >> 11) & 3) + 1)
                                        * (fp->maxpacksize & 0x7ff);
                fp->attributes = parse_uac_endpoint_attributes(chip, alts, protocol, iface_no);
+               fp->clock = clock;
 
                /* some quirks for attributes here */
 
 
 #include "quirks.h"
 #include "helper.h"
 #include "debug.h"
+#include "clock.h"
 
 /*
  * parse the audio format type I descriptor
        struct usb_device *dev = chip->dev;
        unsigned char tmp[2], *data;
        int i, nr_rates, data_size, ret = 0;
+       int clock = snd_usb_clock_find_source(chip, chip->ctrl_intf, fp->clock);
 
        /* get the number of sample rates first by only fetching 2 bytes */
        ret = snd_usb_ctl_msg(dev, usb_rcvctrlpipe(dev, 0), UAC2_CS_RANGE,
                              USB_TYPE_CLASS | USB_RECIP_INTERFACE | USB_DIR_IN,
-                             UAC2_CS_CONTROL_SAM_FREQ << 8, chip->clock_id << 8,
+                             UAC2_CS_CONTROL_SAM_FREQ << 8, clock << 8,
                              tmp, sizeof(tmp), 1000);
 
        if (ret < 0) {
-               snd_printk(KERN_ERR "unable to retrieve number of sample rates\n");
+               snd_printk(KERN_ERR "%s(): unable to retrieve number of sample rates (clock %d)\n",
+                               __func__, clock);
                goto err;
        }
 
 
        /* now get the full information */
        ret = snd_usb_ctl_msg(dev, usb_rcvctrlpipe(dev, 0), UAC2_CS_RANGE,
-                              USB_TYPE_CLASS | USB_RECIP_INTERFACE | USB_DIR_IN,
-                              UAC2_CS_CONTROL_SAM_FREQ << 8, chip->clock_id << 8,
-                              data, data_size, 1000);
+                             USB_TYPE_CLASS | USB_RECIP_INTERFACE | USB_DIR_IN,
+                             UAC2_CS_CONTROL_SAM_FREQ << 8, clock << 8,
+                             data, data_size, 1000);
 
        if (ret < 0) {
-               snd_printk(KERN_ERR "unable to retrieve sample rate range\n");
+               snd_printk(KERN_ERR "%s(): unable to retrieve sample rate range (clock %d)\n",
+                               __func__, clock);
                ret = -EINVAL;
                goto err_free;
        }
 
 #include "urb.h"
 #include "helper.h"
 #include "pcm.h"
+#include "clock.h"
 
 /*
  * return the current pcm pointer.  just based on the hwptr_done value.
        return -EINVAL;
 }
 
-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)) {
-               snd_printk(KERN_WARNING "%d:%d:%d: endpoint lacks sample rate attribute bit, cannot set.\n",
-                                  dev->devnum, iface, fmt->altsetting);
-               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), 1000)) < 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), 1000)) < 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;
-
-       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, chip->clock_id << 8,
-                                  data, sizeof(data), 1000)) < 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, chip->clock_id << 8,
-                                  data, sizeof(data), 1000)) < 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:
-               return set_sample_rate_v1(chip, iface, alts, fmt, rate);
-
-       case UAC_VERSION_2:
-               return set_sample_rate_v2(chip, iface, alts, fmt, rate);
-       }
-
-       return -EINVAL;
-}
-
 /*
  * find a matching format and set up the interface
  */
 
        int num_interfaces;
        int num_suspended_intf;
 
-       /* for audio class v2 */
-       int clock_id;
-
        struct list_head pcm_list;      /* list of pcm streams */
        int pcm_devs;
 
        int setup;                      /* from the 'device_setup' module param */
        int nrpacks;                    /* from the 'nrpacks' module param */
        int async_unlink;               /* from the 'async_unlink' module param */
+
+       struct usb_host_interface *ctrl_intf;   /* the audio control interface */
 };
 
 /*