Re: [alsa-devel] focusrite scarlett 18i20 : Mixer controls with corrupted names for

Am 25.06.19 um 09:54 schrieb Takashi Iwai:

On Sat, 22 Jun 2019 22:55:25 +0200, Stefan Sauer wrote:

...

So the first 8 controls are added somewhere else. Looks like this is from mixer.c and after echo -n 'file sound/usb/mixer.c +p' >/sys/kernel/debug/dynamic_debug/control I get [ 4405.855432] usb 1-2: [51] PU [KKKKKKKKKKKKKÃÃÃÃÃÃÃÃÃÃÃ Switch] ch = 1, val = 0/1 [ 4405.856423] usb 1-2: [52] PU [ Switch] ch = 1, val = 0/1

This indicates that these weird names come from the two extension units id 51 and 52. Could you put some debug print in build_audio_procunit() like below?

I traced it down to this part from sound/usb/mixer.c: nameid = uac_processing_unit_iProcessing(desc, state->mixer->protocol); usb_audio_dbg(state->chip, "desc->bUnitID=%d, proto=%d, nameid=%d\n", desc->bUnitID, state->mixer->protocol, nameid); len = 0; if (nameid) { len = snd_usb_copy_string_desc(state->chip, nameid, kctl->id.name, sizeof(kctl->id.name)); usb_audio_dbg(state->chip, "nameid=%d, len=%d, fallback name='%s'\n", nameid, len, name); }

[ 6241.045734] usb 1-2: desc->bUnitID=51, proto=32, nameid=90 [ 6241.045861] usb 1-2: nameid=90, len=35, fallback name='Extension Unit' [ 6241.045868] usb 1-2: [51] PU [KKKKKKKKKKKKKÃÃÃÃÃÃÃÃÃÃÃ Switch] ch = 1, val = 0/1 [ 6241.046745] usb 1-2: desc->bUnitID=52, proto=32, nameid=82 [ 6241.046857] usb 1-2: nameid=82, len=1, fallback name='Extension Unit' [ 6241.046862] usb 1-2: [52] PU [ Switch] ch = 1, val = 0/1

The device is using UAC_VERSION_2. The code in include/uapi/linux/usb/audio.h is a bit hard to read since uac_mixer_unit_descriptor has a variable length and the code is adding several offset, I'll need to add more printfs there to check if it is correct. I am consulting https://www.usb.org/sites/default/files/audio10.pdf but I am not sure if this covers UAC2.

Stefan

thanks,

Takashi

--- a/sound/usb/mixer.c +++ b/sound/usb/mixer.c @@ -2358,8 +2358,10 @@ static int build_audio_procunit(struct mixer_build *state, int unitid, for (info = list; info && info->type; info++) if (info->type == type) break;

• if (!info || !info->type)

• if (!info || !info->type) {

• pr_info("XXX unit %d to default_info\n", unitid);
  

  info = &default_info;

• }

  for (valinfo = info->values; valinfo->control; valinfo++) { __u8 *controls = uac_processing_unit_bmControls(desc, state->mixer->protocol);

@@ -2375,8 +2377,11 @@ static int build_audio_procunit(struct mixer_build *state, int unitid, }

map = find_map(state->map, unitid, valinfo->control);

• if (map)
  

• 	pr_info("XXX map found for unit %d\n", unitid);
  

  if (check_ignored_ctl(map)) continue;
• cval = kzalloc(sizeof(*cval), GFP_KERNEL); if (!cval) return -ENOMEM;

@@ -2444,19 +2449,26 @@ static int build_audio_procunit(struct mixer_build *state, int unitid, kctl->private_free = snd_usb_mixer_elem_free;

if (check_mapped_name(map, kctl->id.name, sizeof(kctl->id.name))) {

• 	pr_info("XXX name copied from map: '%s' for unit %d\n", kctl->id.name, unitid);
  /* nothing */ ;
  

  } else if (info->name) { strlcpy(kctl->id.name, info->name, sizeof(kctl->id.name));

• 	pr_info("XXX name copied from info: '%s' for unit %d\n", kctl->id.name, unitid);
  

  } else { nameid = uac_processing_unit_iProcessing(desc, state->mixer->protocol);

• 	pr_info("XXX nameid=%d, unit %d\n", nameid, unitid);
  len = 0;
  

• 	if (nameid)
  

• 	if (nameid) {
  	len = snd_usb_copy_string_desc(state->chip,
  				       nameid,
  				       kctl->id.name,
  				       sizeof(kctl->id.name));
  

• 	if (!len)
  

• 		pr_info("XXX copy string desc '%s'\n", kctl->id.name);
  

• 	}
  

• 	if (!len) {
  	strlcpy(kctl->id.name, name, sizeof(kctl->id.name));
  

• 		pr_info("XXX copy default name '%s'\n", kctl->id.name);
  

• 	}
  

  } append_ctl_name(kctl, " "); append_ctl_name(kctl, valinfo->suffix);

---

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