[PATCH 05/14] drm/nouveau: Don't register backlight when another backlight should be used

[Lyude Paul]

Reviewed-by: Lyude Paul <lyude at redhat.com>

Also, ack on this being pushed to drm-misc, along with any other patches I r-b

On Tue, 2022-05-17 at 17:23 +0200, Hans de Goede wrote:
> Before this commit when we want userspace to use the acpi_video backlight
> device we register both the GPU's native backlight device and acpi_video's
> firmware acpi_video# backlight device. This relies on userspace preferring
> firmware type backlight devices over native ones.
> 
> Registering 2 backlight devices for a single display really is
> undesirable, don't register the GPU's native backlight device when
> another backlight device should be used.
> 
> Signed-off-by: Hans de Goede <hdegoede at redhat.com>
> ---
>  drivers/gpu/drm/nouveau/nouveau_backlight.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/gpu/drm/nouveau/nouveau_backlight.c
> b/drivers/gpu/drm/nouveau/nouveau_backlight.c
> index daf9f87477ba..f56ff797c78c 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_backlight.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_backlight.c
> @@ -34,6 +34,8 @@
>  #include <linux/backlight.h>
>  #include <linux/idr.h>
>  
> +#include <acpi/video.h>
> +
>  #include "nouveau_drv.h"
>  #include "nouveau_reg.h"
>  #include "nouveau_encoder.h"
> @@ -404,6 +406,11 @@ nouveau_backlight_init(struct drm_connector *connector)
>                 goto fail_alloc;
>         }
>  
> +       if (acpi_video_get_backlight_type(true) != acpi_backlight_native) {
> +               NV_INFO(drm, "Skipping nv_backlight registration\n");
> +               goto fail_alloc;
> +       }
> +
>         if (!nouveau_get_backlight_name(backlight_name, bl)) {
>                 NV_ERROR(drm, "Failed to retrieve a unique name for the
> backlight interface\n");
>                 goto fail_alloc;

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat