/dev/sequencer descriptions

[Andrey Konovalov]

On Mon, Jul 27, 2020 at 8:02 PM Takashi Iwai <tiwai at suse.de> wrote:
>
> 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.

OK, got it, thank you!