[alsa-devel] aplay -l vs. aplay -L: Missing PCMs?

[Stephen Warren]

Jaroslav Kysela wrote:
> 
> On Fri, 20 Aug 2010, Stephen Warren wrote:
> 
> > Jaroslav Kysela wrote:
> >>
> >> On Thu, 19 Aug 2010, Stephen Warren wrote:
> >>
> >>> The Azalia controller on NVIDIA GPUs gives 4 ALSA hw devices:
> >>>
> >>> (on card 1):
> >>>
> >>> [swarren at swarren-lx2 ~]$ sudo aplay -l
> >>> << includes hw=1,3 hw=1,7 hw=1,8 hw=1,9 >>
> >>> ... all of which appear to work OK.
> >>>
> >>> However, the list of available "PCMs" from aplay -L doesn't expose them all:
> >>>
> >>> [swarren at swarren-lx2 ~]$ sudo aplay -L
> >>> <<card 0 "Nvidia" elided>>
> >>> hdmi:CARD=NVidia_1
> >>>    HDA NVidia, NVIDIA HDMI
> >>>    HDMI Audio Output
> >>>
> >>> Instead, I imagined that I'd see 4 PCMs listed by "aplay -L"; one for each
> >>> converter. Is this an incorrect assumption? How would I make that happen?
> >>
> >> There is a bug in alsa-lib to namehint.c. The code assumes that hw device
> >> number is similar to logical device numbers which is not true in case of
> >> your HDMI devices:
> >>
> >> 3, 7, 8, 9
> >>
> >> The fallback code is used and only first logical device 0 is created.
> >>
> >> Could you test this patch?
> >>
> >> http://git.alsa-project.org/?p=alsa-lib.git;a=commitdiff;h=97d25c0766405453d3c298bd51dd4916121a4f6a
> >
> > I tested that, and unfortunately it doesn't seem to work; I get the exact same
> > aplay -L output.
> >
> > I debugged this a little, and see that add_card() is calculating the correct
> > max_devices value for card=1 str=hdmi. However, in the loop that right after
> > that calls try_config, when device=0, it returns 0, but when device=1, it
> > returns -2 (-ENOENT). This happens inside try_config where it calls
> > snd_config_search_definition (line 244 in latest git). At that point, buf is:
> >
> > hdmi:CARD=NVidia_1,DEV=1
> >
> > ... which seems reasonable.
> >
> > I'm a little confused about the device numbering though: The max_devices
> > value is counting values "3, 7, 8, 9" and hence gets 9. However, the
> > loop that calls try_config loops 0..max_devices-1, but bails out as soon
> > as any error is found, thus disallowing "holes" in the numbering. That
> > implies that "device" in that loop is a different numbering space? After
> > I noticed that, I hacked that loop to continue instead of break on
> > errors, and also removed the "err >= 0" condition from the loop,
> > expecting that when device==3/7/8/9, try_config might work. In fact, 0
> > still works (of course) and 1..8 all fail with err=-2, so I assume at
> > the same place in try_config.
> 
> See my description. It's assumed that the logical devices
> (hdmi:DEV=<logical_device>) are continous. Does
> 'aplay -D hdmi:CARD=NVidia_1,DEV=1' work in your system?

Sure, the logical device IDs should be contiguous. But then, I don't see why
the code would need to calculate max_devices (which is max HW device ID and
hence something other than logical device ID). Anyway...

[swarren at swarren-lx2 ~]$ aplay -D hw:1,7 Shamisen-C4.wav 
Playing WAVE 'Shamisen-C4.wav' : Signed 16 bit Little Endian, Rate 44100 Hz, Stereo

[swarren at swarren-lx2 ~]$ aplay -D hdmi:CARD=NVidia_1,DEV=1 Shamisen-C4.wav 
ALSA lib confmisc.c:1286:(snd_func_refer) Unable to find definition 'cards.HDA-Intel.pcm.hdmi.1:CARD=NVidia_1,AES0=4,AES1=130,AES2=0,AES3=2'
ALSA lib conf.c:4170:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory
ALSA lib conf.c:4649:(snd_config_expand) Evaluate error: No such file or directory
ALSA lib pcm.c:2229:(snd_pcm_open_noupdate) Unknown PCM hdmi:CARD=NVidia_1,DEV=1
aplay: main:608: audio open error: No such file or directory

-- 
nvpublic