ACPI video: if no ACPI backlight support, use vendor drivers
If an ACPI graphics device supports backlight brightness functions (cmp. with
latest ACPI spec Appendix B), let the ACPI video driver control backlight and
switch backlight control off in vendor specific ACPI drivers (asus_acpi,
thinkpad_acpi, eeepc, fujitsu_laptop, msi_laptop, sony_laptop, acer-wmi).
Currently it is possible to load above drivers and let both poke on the
brightness HW registers, the video and vendor specific ACPI drivers -> bad.
This patch provides the basic support to check for BIOS capabilities before
driver loading time. Driver specific modifications are in separate follow up
patches.
"acpi_backlight=vendor"
Prever vendor driver over ACPI driver for backlight.
"acpi_backlight=video" (default)
Prever ACPI driver over vendor driver for backlight.
Signed-off-by: Thomas Renninger <trenn@suse.de>
Acked-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index c86c074..dd5013f 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -198,6 +198,18 @@
that require a timer override, but don't have
HPET
+ acpi_backlight= [HW,ACPI]
+ acpi_backlight=vendor
+ acpi_backlight=video
+ If set to vendor, prefer vendor specific driver
+ (e.g. thinkpad_acpi, sony_acpi, etc.) instead
+ of the ACPI video.ko driver.
+
+ acpi_display_output= [HW,ACPI]
+ acpi_display_output=vendor
+ acpi_display_output=video
+ See above.
+
acpi.debug_layer= [HW,ACPI]
Format: <int>
Each bit of the <int> indicates an ACPI debug layer,