Quick followup. Here is the lsusb -v output for the device: https://gist.github.com/ensonic/2d286a85bbf4aca25e6f36b3569849c3 I noticed two warnings: Warning: Junk at end of descriptor (17 bytes): ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff 00 00 Could those be the cause? I don't now how to map the 'nameid' index to anything in the lsub output though. Am 22.06.19 um 22:55 schrieb Stefan Sauer: > Hi, > > when I run > amixer -D hw:4 controls | sort -n -t = -k2 > > I get the output below > > numid=1,iface=MIXER,name='KKKKKKKKKKKKKÃÃÃÃÃÃÃÃÃÃÃ Switch' > numid=2,iface=CARD,name='Internal Validity' > numid=3,iface=CARD,name='S/PDIF Validity' > numid=4,iface=CARD,name='ADAT Validity' > numid=5,iface=MIXER,name='Scarlett 18i20 USB-Sync Clock Source' > numid=6,iface=MIXER,name=' Switch' > numid=7,iface=CARD,name='Keep Interface' > numid=8,iface=MIXER,name='Master Playback Switch' > numid=9,iface=MIXER,name='Master Playback Volume' > numid=10,iface=MIXER,name='Master 1 (Monitor) Playback Switch' > numid=11,iface=MIXER,name='Master 1 (Monitor) Playback Volume' > ... lots of extra lines ... > > Please note the lines for numid=1 and numid=6. The first one contains some > garbage and the 2nd one look like it should start with another word. > > I now added some debug printing here: > https://github.com/torvalds/linux/blob/master/sound/usb/mixer_scarlett.c#L562 > > and get output in dmesg: > [ 2971.642137] usb 1-2: Product: Scarlett 18i20 USB > [ 2971.642141] usb 1-2: Manufacturer: Focusrite > [ 2971.709773] new ctrl: name='Master Playback Switch', index=10, offset=1, > num=0: numid=8 > [ 2971.709781] new ctrl: name='Master Playback Volume', index=10, offset=2, > num=0: numid=9 > [ 2971.709788] new ctrl: name='Master 1 (Monitor) Playback Switch', index=10, > offset=1, num=1: numid=10 > > 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 > > I now added more debug prints into > https://github.com/torvalds/linux/blob/master/sound/usb/mixer.c#L2431 > and its the code that calls snd_usb_copy_string_desc() > [ 5750.124123] usb 1-2: nameid=90, len=35 > [ 5750.124157] usb 1-2: [51] PU [KKKKKKKKKKKKKÃÃÃÃÃÃÃÃÃÃÃ Switch] ch = 1, val = 0/1 > [ 5750.125241] usb 1-2: nameid=82, len=1 > [ 5750.125260] usb 1-2: [52] PU [ Switch] ch = 1, val = 0/1 > > In both cases the returned len seems wrong and the function does not seems to > copy any useful string here. snd_usb_copy_string_desc() is just a wrapper around > usb_string(). > > Is my hardware returning bogus data in usb descriptors? Can this be address > through some quirks table? Any other ideas? > > Thanks! > Stefan > _______________________________________________ > Alsa-devel mailing list > Alsa-devel@xxxxxxxxxxxxxxxx > https://mailman.alsa-project.org/mailman/listinfo/alsa-devel > _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx https://mailman.alsa-project.org/mailman/listinfo/alsa-devel
