Re: [PATCH v2 03/29] drm/amdgpu: Don't register backlight when another backlight should be used

[Alex Deucher <alexdeucher@gmail.com>]

On Tue, Jul 12, 2022 at 3:39 PM Hans de Goede <hdegoede@redhat.com> 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.
>
> Changes in v2:
> - To avoid linker errors when amdgpu is builtin and video_detect.c is in
>   a module, select ACPI_VIDEO and its deps if ACPI && X86 are enabled.
>   When these are not set, ACPI_VIDEO is disabled, ensuring the stubs
>   from acpi/video.h will be used.
>
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Acked-by: Alex Deucher <alexander.deucher@amd.com>

> ---
>  drivers/gpu/drm/Kconfig                           | 6 ++++++
>  drivers/gpu/drm/amd/amdgpu/atombios_encoders.c    | 7 +++++++
>  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 7 +++++++
>  3 files changed, 20 insertions(+)
>
> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> index aaa7ad1f0614..d65119860760 100644
> --- a/drivers/gpu/drm/Kconfig
> +++ b/drivers/gpu/drm/Kconfig
> @@ -258,6 +258,12 @@ config DRM_AMDGPU
>         select HWMON
>         select BACKLIGHT_CLASS_DEVICE
>         select INTERVAL_TREE
> +       # amdgpu depends on ACPI_VIDEO when X86 and ACPI are both enabled
> +       # for select to work, ACPI_VIDEO's dependencies must also be selected
> +       select INPUT if ACPI && X86
> +       select X86_PLATFORM_DEVICES if ACPI && X86
> +       select ACPI_WMI if ACPI && X86
> +       select ACPI_VIDEO if ACPI && X86
>         help
>           Choose this option if you have a recent AMD Radeon graphics card.
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/atombios_encoders.c b/drivers/gpu/drm/amd/amdgpu/atombios_encoders.c
> index fa7421afb9a6..abf209e36fca 100644
> --- a/drivers/gpu/drm/amd/amdgpu/atombios_encoders.c
> +++ b/drivers/gpu/drm/amd/amdgpu/atombios_encoders.c
> @@ -26,6 +26,8 @@
>
>  #include <linux/pci.h>
>
> +#include <acpi/video.h>
> +
>  #include <drm/drm_crtc_helper.h>
>  #include <drm/amdgpu_drm.h>
>  #include "amdgpu.h"
> @@ -184,6 +186,11 @@ void amdgpu_atombios_encoder_init_backlight(struct amdgpu_encoder *amdgpu_encode
>         if (!(adev->mode_info.firmware_flags & ATOM_BIOS_INFO_BL_CONTROLLED_BY_GPU))
>                 return;
>
> +       if (!acpi_video_backlight_use_native()) {
> +               DRM_INFO("Skipping amdgpu atom DIG backlight registration\n");
> +               return;
> +       }
> +
>         pdata = kmalloc(sizeof(struct amdgpu_backlight_privdata), GFP_KERNEL);
>         if (!pdata) {
>                 DRM_ERROR("Memory allocation failed\n");
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index 5eb111d35793..3b03a95e59a8 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -86,6 +86,8 @@
>  #include <drm/drm_audio_component.h>
>  #include <drm/drm_gem_atomic_helper.h>
>
> +#include <acpi/video.h>
> +
>  #include "ivsrcid/dcn/irqsrcs_dcn_1_0.h"
>
>  #include "dcn/dcn_1_0_offset.h"
> @@ -4050,6 +4052,11 @@ amdgpu_dm_register_backlight_device(struct amdgpu_display_manager *dm)
>         amdgpu_dm_update_backlight_caps(dm, dm->num_of_edps);
>         dm->brightness[dm->num_of_edps] = AMDGPU_MAX_BL_LEVEL;
>
> +       if (!acpi_video_backlight_use_native()) {
> +               DRM_INFO("Skipping amdgpu DM backlight registration\n");
> +               return;
> +       }
> +
>         props.max_brightness = AMDGPU_MAX_BL_LEVEL;
>         props.brightness = AMDGPU_MAX_BL_LEVEL;
>         props.type = BACKLIGHT_RAW;
> --
> 2.36.0
>