The Lenovo ThinkPad W530 uses a nvidia k1000m GPU. When this gets used together with one of the older nvidia binary driver series (the latest series does not support it), then backlight control does not work.

This is caused by commit 3dbc80a3e4c5 ("ACPI: video: Make backlight class device registration a separate step (v2)") combined with commit 5aa9d943e9b6 ("ACPI: video: Don't enable fallback path for creating ACPI backlight by default").

After these changes the acpi_video# backlight device is only registered when requested by a GPU driver calling acpi_video_register_backlight() which the nvidia binary driver does not do.

I realize that using the nvidia binary driver is not a supported use-case and users can workaround this by adding acpi_backlight=video on the kernel commandline, but the ThinkPad W530 is a popular model under Linux users, so it seems worthwhile to add a quirk for this.

I will also email Nvidia asking them to make the driver call acpi_video_register_backlight() when an internal LCD panel is detected. So maybe the next maintenance release of the drivers will fix this...

Fixes: 5aa9d943e9b6 ("ACPI: video: Don't enable fallback path for creating ACPI backlight by default") Cc: stable@vger.kernel.org Reviewed-by: Mario Limonciello mario.limonciello@amd.com Signed-off-by: Hans de Goede hdegoede@redhat.com --- drivers/acpi/video_detect.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+)

diff --git a/drivers/acpi/video_detect.c b/drivers/acpi/video_detect.c index 295744fe7c92..e85729fc481f 100644 --- a/drivers/acpi/video_detect.c +++ b/drivers/acpi/video_detect.c @@ -299,6 +299,20 @@ static const struct dmi_system_id video_detect_dmi_table[] = { }, },

+ /* + * Older models with nvidia GPU which need acpi_video backlight + * control and where the old nvidia binary driver series does not + * call acpi_video_register_backlight(). + */ + { + .callback = video_detect_force_video, + /* ThinkPad W530 */ + .matches = { + DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"), + DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad W530"), + }, + }, + /* * These models have a working acpi_video backlight control, and using * native backlight causes a regression where backlight does not work