[alsa-devel] ALSA: hda: hdmi: Hint matching between input devices and pcm devices

[Takashi Iwai]

At Tue, 30 Aug 2011 08:01:50 -0500,
Pierre-Louis Bossart wrote:
> 
> Hi Clemens,
> 
> > If the driver can detect ELD changes, it must inform userspace that
> > the control has changed.  If there is no ELD, the _get callback should
> > return an error, and the control should have been set to unreadable.
> 
> Bear with my ignorance of controls, but how does the driver 'inform
> userspace that the control has changed'?

The control API has a notification mechanism.  You can find some
drivers calling snd_ctl_notify().


Takashi