Re: 42fdcd9fd917 broke my snd_uaudio(4)

hi Florian,

Florian Walpen:
> I have a Scarlett 18i20 myself, but maybe a different generation - it has 18 
> recording channels as its name suggests. Is 20 recording channels correct for 
> your device?
 
this is a 3rd generation 18i20; as well the usual physical inputs it has
a stereo loopback channel that can be configured in the built-in mixer
and which appears as an additional two recording channels.  i think
(although i'm not certain) that loopback functionality is new in the 3rd
generation model.

this is (very briefly) documented in the manual, which doesn't really
add anything to what i just said but does show a screenshot of Ableton
with 20 channels on p.16, which matches how the interface appeared in
Logic when i used it there:

https://fael-downloads-prod.focusrite.com/customer/prod/downloads/scarlett_18i20_3rd_gen_user_guide_v3_english_en.pdf

> > FreeBSD Audio Driver (64bit 2009061500/amd64)
> > Installed devices:
> > pcm0: <Focusrite Scarlett 18i20 USB> on uaudio0 (1p:0v/1r:0v) default
> > 	snddev
> > flags=0x3e6<AUTOVCHAN,SOFTPCMVOL,BUSY,MPSAFE,REGISTERED,BITPERFECT,VPC>
> > [pcm0:play:dsp0.p0]: spd 48000, fmt 0x01401000, flags 0x2000110c,
> > 0x00000001, pid 22326 (virtual_oss) interrupts 115908, underruns 0, feed
> > 115907, ready 123440 [b:30720/15360/2|bs:131040/65520/2] channel
> > flags=0x2000110c<RUNNING,TRIGGERED,BUSY,HAS_SIZE,BITPERFECT> {userland} ->
> > feeder_root(0x01401000) -> {hardware}
> > 	[pcm0:record:dsp0.r0]: spd 48000, fmt 0x01401000, flags 0x2000112c,
> > 0x00000001, pid 22326 (virtual_oss) interrupts 115930, overruns 97, feed
> > 229796, hfree 30720, sfree 65440 [b:30720/15360/2|bs:65440/32720/2] channel
> > flags=0x2000112c<RUNNING,TRIGGERED,SLEEPING,BUSY,HAS_SIZE,BITPERFECT>
> > {hardware} -> feeder_root(0x01401000) -> {userland}
> > Installed devices from userspace:
> > dsp.full: <Virtual OSS> (play/rec)
> > dsp.record: <Virtual OSS> (play/rec)
> > dsp: <Virtual OSS> (play/rec)
> 
> I see that there's a lot of recording overruns and the recording software side 
> buffer of the pcm device is unusually small. Does recording work well for you?
 
i haven't had a chance to test recording yet beyond a single work
conference call, as i've only just got playback working well (that
required a lot of fiddling with various options until i settled on
virtual_oss).

if you can suggset any obvious changes i'd appreciate that - maybe it's
just a case of increasing the virtual_oss buffer?  i did have to
increase the playback buffer a bit as the virtual_oss default is rather
small.

> Apart from that, I'd be interested in the exact circumstances this problem 
> occurs. Could you provide the dmesg and sndstat output as above, but with the 
> settings in loader.conf applied and playback hanging?
 
> Since you're using virtual_oss, I suppose it produces an error log somewhere? 
> And then maybe the output of the following commands, also while playback is 
> hanging:
> 
> sysctl hw.snd
> sysctl dev.pcm.0

i'll open a bug with this and the other details once i get a chance to
reboot again to test, probably later today.

	thanks, lexi.