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

[Hans de Goede]

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 at redhat.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