[alsa-devel] HDMI codec, way forward?

[Takashi Iwai]

On Sun, 18 Oct 2015 19:16:42 +0200,
Russell King - ARM Linux wrote:
> 
> On Sun, Oct 18, 2015 at 09:43:29PM +0530, Vinod Koul wrote:
> > Right but can I ask why you didn't try making video as component and then
> > CEC, audio and others receive the notification over this.
> 
> Okay, I think I see what you're getting at.  No, I don't want to tie
> this stuff into the component helpers because that's the wrong approach.
> 
> The component helper is purely about combining several struct devices
> into one larger component for a subsystem which deals with card-level
> components.  It's not about cross-subsystem stuff.
> 
> The problem with using it for cross-subsystem stuff is that it becomes
> too tightly bound together: why should the graphics side get torn down
> if you unload the audio or CEC driver?
> 
> Audio and CEC are rather optional for HDMI - HDMI can work without audio
> and CEC being present.  However, audio can't be conveyed across the link
> without the video side being configured.  So, it makes sense to allow
> the CEC and audio parts to be loaded separately (possibly as modules)
> while having the video parts built-in to the kernel - especially if you
> want to use the HDMI output as the console.
> 
> Binding CEC and audio into the component helper alongside the video part
> will mean that nothing will come up until all the components are present,
> and everything will be torn down when any one of those components are
> removed.  Clearly, that's undesirable.

Currently i915/audio component works as you described.  The audio is
optional and HDMI graphics works without audio, while HDMI HD-audio
mandates i915 graphics.


Takashi