[alsa-devel] HDMI codec, way forward?

[Russell King - ARM Linux]

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.

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