drm/radeon: Don't register backlight when another backlight should be used (v3)

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 is enabled.
  When ACPI is disabled, ACPI_VIDEO is also always disabled, ensuring
  the stubs from acpi/video.h will be used.

Changes in v3:
- Use drm_info(drm_dev, "...") to log messages
- ACPI_VIDEO can now be enabled on non X86 too,
  adjust the Kconfig changes to match this.

Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

2 files changed, 14 insertions, 0 deletions

diff --git a/drivers/gpu/drm/radeon/atombios_encoders.c b/drivers/gpu/drm/radeon/atombios_encoders.c
index c93040e60d04..2b01edea8fe8 100644
--- a/drivers/gpu/drm/radeon/atombios_encoders.c
+++ b/drivers/gpu/drm/radeon/atombios_encoders.c
@@ -32,6 +32,8 @@
 #include <drm/drm_file.h>
 #include <drm/radeon_drm.h>
 
+#include <acpi/video.h>
+
 #include "atom.h"
 #include "radeon_atombios.h"
 #include "radeon.h"
@@ -209,6 +211,11 @@ void radeon_atom_backlight_init(struct radeon_encoder *radeon_encoder,
 	if (!(rdev->mode_info.firmware_flags & ATOM_BIOS_INFO_BL_CONTROLLED_BY_GPU))
 		return;
 
+	if (!acpi_video_backlight_use_native()) {
+		drm_info(dev, "Skipping radeon atom DIG backlight registration\n");
+		return;
+	}
+
 	pdata = kmalloc(sizeof(struct radeon_backlight_privdata), GFP_KERNEL);
 	if (!pdata) {
 		DRM_ERROR("Memory allocation failed\n");
diff --git a/drivers/gpu/drm/radeon/radeon_legacy_encoders.c b/drivers/gpu/drm/radeon/radeon_legacy_encoders.c
index 1a66fb969ee7..0cd32c65456c 100644
--- a/drivers/gpu/drm/radeon/radeon_legacy_encoders.c
+++ b/drivers/gpu/drm/radeon/radeon_legacy_encoders.c
@@ -33,6 +33,8 @@
 #include <drm/drm_util.h>
 #include <drm/radeon_drm.h>
 
+#include <acpi/video.h>
+
 #include "radeon.h"
 #include "radeon_asic.h"
 #include "radeon_legacy_encoders.h"
@@ -387,6 +389,11 @@ void radeon_legacy_backlight_init(struct radeon_encoder *radeon_encoder,
 		return;
 #endif
 
+	if (!acpi_video_backlight_use_native()) {
+		drm_info(dev, "Skipping radeon legacy LVDS backlight registration\n");
+		return;
+	}
+
 	pdata = kmalloc(sizeof(struct radeon_backlight_privdata), GFP_KERNEL);
 	if (!pdata) {
 		DRM_ERROR("Memory allocation failed\n");