ALSA: usb-audio: parse clock topology of UAC2 devices

Audio devices which comply to the UAC2 standard can export complex clock
topologies in its descriptors and set up links between them.

The entities that are defined are

 - clock sources, which define the end-leafs.
 - clock selectors, which act as switch to select one out of many
   possible clocks sources.
 - clock multipliers, which have an input clock source, and act as clock
   source again. They can be used to derive one clock from another.

All sample rate changes, clock validity queries and the like must go to
clock source elements, while clock selectors and multipliers can be used
as terminal clock source.

The following patch adds a parser for these elements and functions to
iterate over the tree and find the leaf nodes (clock sources).

The samplerate set functions were moved to the new clock.c file.

Signed-off-by: Daniel Mack <daniel@caiaq.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 55 insertions, 2 deletions

diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
index 28ee1ce3971a..9593b91452b9 100644
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -190,6 +190,38 @@ static int parse_uac_endpoint_attributes(struct snd_usb_audio *chip,
         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;
@@ -199,7 +231,7 @@ int snd_usb_parse_audio_endpoints(struct snd_usb_audio *chip, int iface_no)
         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;
@@ -263,6 +295,8 @@ int snd_usb_parse_audio_endpoints(struct snd_usb_audio *chip, int iface_no)
                 }
 
                 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);
 
@@ -281,7 +315,25 @@ int snd_usb_parse_audio_endpoints(struct snd_usb_audio *chip, int iface_no)
                         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:
@@ -338,6 +390,7 @@ int snd_usb_parse_audio_endpoints(struct snd_usb_audio *chip, int iface_no)
                         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 */