How to hook HDMI audio to vga-switcher?

[Dave Airlie]

On Wed, Apr 25, 2012 at 9:36 AM, Takashi Iwai <tiwai at suse.de> wrote:
> Hi Dave,
>
> in kernel bug 43155, we found out that the HDMI audio controller on
> AMD graphics is also disabled when the graphics chip is disabled via
> vga-switcher:
>    https://bugzilla.kernel.org/show_bug.cgi?id=43155
>
> This screws up the sound driver, takes too long time for boot.
>
> Since the audio controller/codec becomes active again once when the
> graphics is turned on, the best solution would be to add a client to
> vga-swicheroo for handling the status of the HDMI audio controller.
>
> But, looking at the current vga_switcheroo.c, it seems that the
> current code assumes only two clients and doesn't consider about
> non-graphics PCI entries.
>
> As a workaround, I'm thiking of a sort of slave client belonging to
> the video client, so that a callback like set_gpu_state() can be
> called.

I'd envisage some sort of notifier interface that other non-gpu
drivers can hook into
to be told about the current state of the GPU device. So some sort of separate
client type with a callback when we turn on/off the device so other drivers can
init themselves.


Dave.