ALSA: usb-audio: clean up find_audio_control_unit()
Use a struct to parse the audio units, and return usable descriptors
for all types. There's no need to limit the result set, except for some
kind of sanity check.
Signed-off-by: Daniel Mack <daniel@caiaq.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
index 8be6bf2..cb345360 100644
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -165,22 +165,24 @@
/*
* find an audio control unit with the given unit id
- * this doesn't return any clock related units, so they need to be handled elsewhere
*/
static void *find_audio_control_unit(struct mixer_build *state, unsigned char unit)
{
- unsigned char *p;
+ /* we just parse the header */
+ struct uac_feature_unit_descriptor *hdr = NULL;
- p = NULL;
- while ((p = snd_usb_find_desc(state->buffer, state->buflen, p,
- USB_DT_CS_INTERFACE)) != NULL) {
- if (p[0] >= 4 && p[2] >= UAC_INPUT_TERMINAL && p[2] <= UAC2_EXTENSION_UNIT_V2 && p[3] == unit)
- return p;
+ while ((hdr = snd_usb_find_desc(state->buffer, state->buflen, hdr,
+ USB_DT_CS_INTERFACE)) != NULL) {
+ if (hdr->bLength >= 4 &&
+ hdr->bDescriptorSubtype >= UAC_INPUT_TERMINAL &&
+ hdr->bDescriptorSubtype <= UAC2_SAMPLE_RATE_CONVERTER &&
+ hdr->bUnitID == unit)
+ return hdr;
}
+
return NULL;
}
-
/*
* copy a string with the given id
*/