[alsa-devel] calling snd_ctl_notify from mixer ctl_put

Ondrej Zary linux at rainbow-software.org
Sat Oct 13 23:23:44 CEST 2012

On Friday 12 October 2012 08:03:13 Clemens Ladisch wrote:
> Ondrej Zary wrote:
> > I want to enable/disable some mixer controls based on state of another
> > control (switching between limiter and AGC mode). So I (re)set the
> > SNDRV_CTL_ELEM_ACCESS_INACTIVE flag in kctl->vd[0].access
> > and then call snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_INFO, &kctl->id);
> > Everyting from ctl_put() mixer callback.
> >
> > When changing the control value in alsamixer, it crashes with:
> > alsamixer: simple.c:948: snd_mixer_selem_get_enum_item: Assertion
> > `(elem)->type == SND_MIXER_ELEM_SIMPLE' failed.
> Looks like a bug in alsamixer.

Thanks. I've now tried some other mixers that are present in Debian and most 
of them are unusable:
alsamixergui: does not understand ENUM controls
gnome-alsamixer: does not understand ENUM controls
gnome-volume-control: crashes like alsamixer
xfce4-mixer: crashes like alsamixer
kmix (TDE 3.5.13): does not update controls when switching limiter/AGC
kmix (KDE 4): crashes like alsamixer
(other mixers won't even run as they seem to be OSS-only)

But there's one that works fine: QasMixer.

Ondrej Zary

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