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ALSA: usb-audio: clean up find_audio_control_unit()

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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>
This commit is contained in:
Daniel Mack 2010-05-31 13:35:43 +02:00 committed by Takashi Iwai
parent 2e0281d15c
commit 67e1daa0bb
1 changed files with 10 additions and 8 deletions
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18
sound/usb/mixer.c
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@ -165,22 +165,24 @@ static int check_mapped_selector_name(struct mixer_build *state, int unitid,
/*
* 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
*/