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

Pierre-Louis Bossart pierre-louis.bossart at linux.intel.com
Tue Aug 30 15:01:50 CEST 2011

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'?

> > Or is there a way to link a control to a specify PCM device?
> Yes: set .iface to _PCM instead of _MIXER (this will also prevent
> 'normal' mixers from showing this control, but a _BYTE control wouldn't
> be shown anyway), and set .device (and .subdevice, if appropriate) to
> the PCM device's (sub)device number.

This is exactly what I wanted, it makes things simpler. Thanks for the

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