Re: [PATCH] platform/raspberrypi: vchiq: register bus at subsys_initcall

[Martin Wetterwald]

On Thu, Oct 15, 2026 at 11:25 PM Gaston Gonzalez <gascoar@xxxxxxxxx> wrote:
> Hi,
>
> For Raspberry Pi Zero v1.3:
>
> Tested-by: Gaston Gonzalez <gascoar@xxxxxxxxx>
>
> Test setup:
>
> - Branch: patch manually applied in staging-next over commit ec1ecf4f23c5
> - Setup: RPi Zero v1.3 connected to a HDMI monitor
> - OS: standard raspbian with the desktop environment enabled
> - Driver built both as a module and built-in.
> - The following command was run to test the sound: 'speaker-test -t wav -c 2'
> - Result: Both HDMI audio channels worked correctly

Hello Gaston,
Thanks very much for your test!
It's great to have variety in tests because I don't have the Pi Zero, and I
didn't test it through HDMI, I tested through the Headphones jack (which
doesn't exist on the Pi Zero).

Did you also also reproduce the bug without adding my patch?
If the bug is present, cat /proc/asound/cards should reveal bcm2835_hdmi and
bcm2835_headphones are both not present. And you should see this in the dmesg:
> Driver 'bcm2835-audio' was unable to register with bus_type 'vchiq-bus' because the bus was not initialized.

Regarding your test: there are two ways for the sound to go through the HDMI
port:
- One is through the bcm2835-audio driver (using VCHIQ)
- The other way is through the vc4-hdmi (bypassing VCHIQ)

  # cat /proc/asound/cards
   0 [vc4hdmi        ]: vc4-hdmi - vc4-hdmi
                        vc4-hdmi
   1 [HDMI           ]: bcm2835_hdmi - bcm2835 HDMI
                        bcm2835 HDMI
   2 [Headphones     ]: bcm2835_headpho - bcm2835 Headphones
                        bcm2835 Headphones

Can you make sure that your HDMI sound is really using bcm2835_hdmi ?
If your sound happens to actually go through vc4-hdmi, then you are not testing
my patch. If you can't see the bcm2835_hdmi, you just need to add:

  snd_bcm2835.enable_hdmi=1

to your kernel command line if the driver is built in, or to the modprobe
command as module parameter.

> I’d be happy to run any additional tests if needed.

It would be interesting to test other "clients" of the VCHIQ bus (because I
only tested bcm2835-audio).
But I've just noticed that bcm2835-camera doesn't exist anymore (it was using
VCHIQ via VCHIQ_MMAL).
If I understand correctly, if VCHIQ_MMAL is still there, it's because the
bcm2835-isp and bcm2835-codec drivers will be upstreamed in the future, but
there is not current "client" in the kernel as far as I understand.

The only remaining thing I can think of is /dev/vchiq (CONFIG_VCHIQ_CDEV).

Thanks again for the tests!
Martin