[alsa-devel] get rid of controls with snd_ctl_remove
Liam Girdwood
lrg at kernel.org
Fri Aug 29 15:16:52 CEST 2008
On Fri, 2008-08-29 at 15:01 +0200, Takashi Iwai wrote:
> At Fri, 29 Aug 2008 14:54:42 +0200,
> Harald Radke wrote:
> >
> > Hi there!
> >
> > Please be patient with me, I am quite inexperienced with alsa programming, so
> > this might be a dumb question:
> >
> > We have a WM8750 working in our PDA, the codec is working so far but I want to
> > remove some of the control since they aren't needed.
> >
> > Instead of copying the wm8750.c file and adjusting it, I want to write another
> > module which basically get rid of those controls, something like:
> >
> > [...]
> >
> > static const char* unused_controls[] = {"AAAA", "BBBB,"CCCC"};
> >
> > struct snd_kcontrol *ctl;
> >
> > list_for_each_entry(ctl, &card->controls, list)
>
> You can't use list_for_each_entry() together with removal.
> Use list_for_each_entry_safe() for such a purpose.
>
> But...
>
> > for(i=0; i < ARRAY_SIZE(unused_controls); i++)
> > if (!strcmp(unused_controls[i],ctl->id.name)) {
> > down_write(&card->controls_rwsem);
> > snd_ctl_remove(card,ctl);
> > up_write(&card->controls_rwsem);
> > break;
> > }
>
> It'd be easier like the following:
>
> for (i = 0; i < ARRAY_SIZE(unused_controls); i++) {
> struct snd_ctl_elem_id id;
> memset(&id, 0, sizeof(id));
> strcpy(id.name, unused_controls[i]);
> id.iface = SNDRV_CTL_ELEM_IFACE_MIXER;
> snd_ctl_remove_id(card, &id);
> }
I'd prefer an addition to our API to handle this more _common_ case
rather than just removing controls.
Something where we can mark controls as "disabled" so alsamixer and
friends wont render/get them. This would also allow scenario code to
disable relevant mixers and then re-enable when required.
Liam
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