/dev/sequencer descriptions

[Takashi Iwai]

On Mon, 27 Jul 2020 19:47:54 +0200,
Andrey Konovalov wrote:
> 
> Hi Takashi,
> 
> We're working on syzkaller descriptions for /dev/sequencer [1], but
> have some troubles understanding its functionality. The main question
> is: is sound/synth/emux/ code reachable when tested in a VM (we're
> using QEMU with -soundhw all), or does it require some specific
> hardware to be present?

It's for Creative SoundBlaster EMU chips, and it needs the specific
hardware that isn't emulated, so far.

> In our setup (with Debian Stretch userspace image) we have
> /dev/sequencer with SNDRV_MINOR_OSS_SEQUENCER and /dev/sequencer2 with
> SNDRV_MINOR_OSS_MUSIC. For the former, there are no synth devices as
> reported by SNDCTL_SEQ_NRSYNTHS. For the latter, synth devices are
> there, but the load_patch() callback is not reachable as this check
> [2] fails.
> 
> Is that code impossible to test in a VM at all? Or are there some
> specific kernel options/drivers that need to be enabled?

Another possible device supporting the OSS sequencer is the old FM
OPL3.  But it seems also not properly implemented in QEMU (I see only
OPL2), unfortunately.


thanks,

Takashi