On Sat, 29 Jun 2019 14:32:21 +0200, Stefan Sauer wrote:
Am 26.06.19 um 23:42 schrieb Takashi Iwai:
On Wed, 26 Jun 2019 22:06:32 +0200, Stefan Sauer wrote:
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?
Thanks for the patch! With that I get nameid=0 for both PUs:
[ 976.445182] usb 1-2: desc->bUnitID=51, proto=32, nameid=0 [ 976.445186] usb 1-2: fallback name='Extension Unit' [ 976.445189] usb 1-2: [51] PU [Extension Unit Switch] ch = 1, val = 0/1 [ 976.446052] usb 1-2: [40] SU [Scarlett 18i20 USB-Sync Clock Source] items = 3 [ 976.446059] usb 1-2: desc->bUnitID=52, proto=32, nameid=0 [ 976.446061] usb 1-2: fallback name='Extension Unit' [ 976.446064] usb 1-2: [52] PU [Extension Unit Switch] ch = 1, val = 0/1
on eocmment for the patch below.
Good, that's the expected behavior. The string index 0 indicates no specific string, so it falls back.
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.
UAC2 is completely different from UAC1, so you can forget that PDF.
I think I found the culprit. The bug was that UAC2 extension unit descriptor has a very slight difference from UAC2 processing unit descriptor: namely, the size of bmControls field is 1 while processing unit has 2. And iExtension follows that, so we're reading a wrong offset.
That's the reason a bogus nameid like 90 is read.
Could you try the patch below?
thanks,
Takashi
--- a/include/uapi/linux/usb/audio.h +++ b/include/uapi/linux/usb/audio.h @@ -450,6 +450,37 @@ static inline __u8 *uac_processing_unit_specific(struct uac_processing_unit_desc } }
+static inline __u8 uac_extension_unit_bControlSize(struct uac_processing_unit_descriptor *desc,
int protocol)+{
- switch (protocol) {
- case UAC_VERSION_1:
return desc->baSourceID[desc->bNrInPins + 4];- case UAC_VERSION_2:
return 1; /* in UAC2, this value is constant */- case UAC_VERSION_3:
return 4; /* in UAC3, this value is constant */- default:
return 1;- }
+}
+static inline __u8 uac_extension_unit_iExtension(struct uac_processing_unit_descriptor *desc,
int protocol)+{
- __u8 control_size = uac_extension_unit_bControlSize(desc, protocol);
- switch (protocol) {
- case UAC_VERSION_1:
- case UAC_VERSION_2:
- default:
return *(uac_processing_unit_bmControls(desc, protocol)+ control_size);if this is for 'extension_units' can we still use the offset helper for 'processing_units'?
Yes, until this point, both extension units and processing units are identical. The difference comes after that.
Is the UAC2 spec available freely, if so with a link, I can probably figure this out.
You should be able to find on the net, I suppose.
In anyway I'm going to prepare the proper patch for merging to upstream.
thanks,
Takashi