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

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

[Martin Wetterwald]

Since the VCHIQ interface was moved out of staging, its bus is no longer
guaranteed to be registered before its client drivers. bcm2835-audio,
still in drivers/staging, registers at device_initcall level and now
runs first:

  Driver 'bcm2835-audio' was unable to register with bus_type
  'vchiq-bus' because the bus was not initialized.

Register the bus and the platform driver at subsys_initcall so the bus
exists before any client driver, independently of link order. The
platform driver probe already returns -EPROBE_DEFER while the firmware
is not ready, so probing earlier is safe. When built as modules, this is
equivalent to module_init() and nothing changes.

Tested on Raspberry Pi 1B rev2, 1B+, 2B, 3B and 4B with VCHIQ and
bcm2835-audio both builtin and both as modules.

Fixes: aa125180c673 ("platform/raspberrypi: Destage VCHIQ interface")
Reported-by: Martin Wetterwald <martin@wetterwald.eu>
Link: https://lore.kernel.org/r/CAFERDQ0FpdVvA5VJxOyRAE_pgxnPVmFx1tkZio5R272j6Bs4tg@mail.gmail.com/
Closes: https://lore.kernel.org/r/CAFERDQ0FpdVvA5VJxOyRAE_pgxnPVmFx1tkZio5R272j6Bs4tg@mail.gmail.com/
Signed-off-by: Martin Wetterwald <martin@wetterwald.eu>
---
 drivers/platform/raspberrypi/vchiq-interface/vchiq_arm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/platform/raspberrypi/vchiq-interface/vchiq_arm.c b/drivers/platform/raspberrypi/vchiq-interface/vchiq_arm.c
index e78641703252..d35f5ac5c2e2 100644
--- a/drivers/platform/raspberrypi/vchiq-interface/vchiq_arm.c
+++ b/drivers/platform/raspberrypi/vchiq-interface/vchiq_arm.c
@@ -1462,7 +1462,7 @@ static int __init vchiq_driver_init(void)
 
 	return ret;
 }
-module_init(vchiq_driver_init);
+subsys_initcall(vchiq_driver_init);
 
 static void __exit vchiq_driver_exit(void)
 {
-- 
2.55.0

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

[Jai Luthra]

Hi Martin,

Thanks for the quick fix.

Quoting Martin Wetterwald (2026-10-13 18:44:35)
> Since the VCHIQ interface was moved out of staging, its bus is no longer
> guaranteed to be registered before its client drivers. bcm2835-audio,
> still in drivers/staging, registers at device_initcall level and now
> runs first:
> 
>   Driver 'bcm2835-audio' was unable to register with bus_type
>   'vchiq-bus' because the bus was not initialized.
> 
> Register the bus and the platform driver at subsys_initcall so the bus
> exists before any client driver, independently of link order. The
> platform driver probe already returns -EPROBE_DEFER while the firmware
> is not ready, so probing earlier is safe. When built as modules, this is
> equivalent to module_init() and nothing changes.
> 
> Tested on Raspberry Pi 1B rev2, 1B+, 2B, 3B and 4B with VCHIQ and
> bcm2835-audio both builtin and both as modules.
> 
> Fixes: aa125180c673 ("platform/raspberrypi: Destage VCHIQ interface")
> Reported-by: Martin Wetterwald <martin@wetterwald.eu>
> Link: https://lore.kernel.org/r/CAFERDQ0FpdVvA5VJxOyRAE_pgxnPVmFx1tkZio5R272j6Bs4tg@mail.gmail.com/
> Closes: https://lore.kernel.org/r/CAFERDQ0FpdVvA5VJxOyRAE_pgxnPVmFx1tkZio5R272j6Bs4tg@mail.gmail.com/
> Signed-off-by: Martin Wetterwald <martin@wetterwald.eu>

Reviewed-by: Jai Luthra <jai.luthra@ideasonboard.com>

Thanks,
  Jai

> ---
>  drivers/platform/raspberrypi/vchiq-interface/vchiq_arm.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/platform/raspberrypi/vchiq-interface/vchiq_arm.c b/drivers/platform/raspberrypi/vchiq-interface/vchiq_arm.c
> index e78641703252..d35f5ac5c2e2 100644
> --- a/drivers/platform/raspberrypi/vchiq-interface/vchiq_arm.c
> +++ b/drivers/platform/raspberrypi/vchiq-interface/vchiq_arm.c
> @@ -1462,7 +1462,7 @@ static int __init vchiq_driver_init(void)
>  
>  	return ret;
>  }
> -module_init(vchiq_driver_init);
> +subsys_initcall(vchiq_driver_init);
>  
>  static void __exit vchiq_driver_exit(void)
>  {
> -- 
> 2.55.0
>

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

[Gaston Gonzalez]

On Tue Oct 13, 2026 at 10:14 AM -03, Martin Wetterwald wrote:
> Since the VCHIQ interface was moved out of staging, its bus is no longer
> guaranteed to be registered before its client drivers. bcm2835-audio,
> still in drivers/staging, registers at device_initcall level and now
> runs first:
>
>   Driver 'bcm2835-audio' was unable to register with bus_type
>   'vchiq-bus' because the bus was not initialized.
>
> Register the bus and the platform driver at subsys_initcall so the bus
> exists before any client driver, independently of link order. The
> platform driver probe already returns -EPROBE_DEFER while the firmware
> is not ready, so probing earlier is safe. When built as modules, this is
> equivalent to module_init() and nothing changes.
>
> Tested on Raspberry Pi 1B rev2, 1B+, 2B, 3B and 4B with VCHIQ and
> bcm2835-audio both builtin and both as modules.
>
> Fixes: aa125180c673 ("platform/raspberrypi: Destage VCHIQ interface")
> Reported-by: Martin Wetterwald <martin@wetterwald.eu>
> Link: https://lore.kernel.org/r/CAFERDQ0FpdVvA5VJxOyRAE_pgxnPVmFx1tkZio5R272j6Bs4tg@mail.gmail.com/
> Closes: https://lore.kernel.org/r/CAFERDQ0FpdVvA5VJxOyRAE_pgxnPVmFx1tkZio5R272j6Bs4tg@mail.gmail.com/
> Signed-off-by: Martin Wetterwald <martin@wetterwald.eu>
> ---
>  drivers/platform/raspberrypi/vchiq-interface/vchiq_arm.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/platform/raspberrypi/vchiq-interface/vchiq_arm.c b/drivers/platform/raspberrypi/vchiq-interface/vchiq_arm.c
> index e78641703252..d35f5ac5c2e2 100644
> --- a/drivers/platform/raspberrypi/vchiq-interface/vchiq_arm.c
> +++ b/drivers/platform/raspberrypi/vchiq-interface/vchiq_arm.c
> @@ -1462,7 +1462,7 @@ static int __init vchiq_driver_init(void)
>  
>  	return ret;
>  }
> -module_init(vchiq_driver_init);
> +subsys_initcall(vchiq_driver_init);
>  
>  static void __exit vchiq_driver_exit(void)
>  {

Hi,

For Raspberry Pi Zero v1.3:

Tested-by: Gaston Gonzalez <gascoar@gmail.com>

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

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

Regards,

Gaston

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

[Martin Wetterwald]

On Thu, Oct 15, 2026 at 11:25 PM Gaston Gonzalez <gascoar@gmail.com> wrote:
> Hi,
>
> For Raspberry Pi Zero v1.3:
>
> Tested-by: Gaston Gonzalez <gascoar@gmail.com>
>
> 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