[PATCH] ACPI: video: force native backlight on Acer Nitro AN515-46

The Acer Nitro AN515-46 is a hybrid graphics laptop whose internal
panel is driven by the AMD GPU (Radeon 680M); the discrete NVIDIA GPU
only drives external outputs. The firmware nevertheless advertises the
NVIDIA WMI EC backlight GUID, so the backlight type resolves to
nvidia_wmi_ec. The nvidia-wmi-ec-backlight driver however fails to
probe ("EC backlight control failed: AE_NOT_FOUND") and, since the
backlight type is still nvidia_wmi_ec, amdgpu skips registering its
own backlight device. The result is no backlight device at all,
leaving the brightness keys and the desktop brightness slider
non-functional.

Booting with acpi_backlight=native makes amdgpu register its backlight
interface and brightness control works. Add a DMI quirk to use the
native backlight on this model by default.

Signed-off-by: Marcos Paulo Medeiros <[email protected]>
---
 drivers/acpi/video_detect.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/acpi/video_detect.c b/drivers/acpi/video_detect.c
index 5b0dc679e..07755b856 100644
--- a/drivers/acpi/video_detect.c
+++ b/drivers/acpi/video_detect.c
@@ -919,6 +919,14 @@ static const struct dmi_system_id video_detect_dmi_table[] = {
 		DMI_MATCH(DMI_PRODUCT_NAME, "OMEN by HP Gaming Laptop 16-n0xxx"),
 		},
 	},
+	{
+	 .callback = video_detect_force_native,
+	 /* Acer Nitro AN515-46 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Acer"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "Nitro AN515-46"),
+		},
+	},
 
 	/*
 	 * x86 android tablets which directly control the backlight through
-- 
2.53.0