drm/i915: panel: invert brightness via quirk
commit 4dca20efb1a9c2efefc28ad2867e5d6c3f5e1955 upstream.
A machine may need to invert the panel backlight brightness value. This
patch adds the infrastructure for a quirk to do so.
Signed-off-by: Carsten Emde <C.Emde@osadl.org>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
[wml: Backported to 3.4:
- Adjust context
- one more flag QUIRK_NO_PCH_PWM_ENABLE]
Signed-off-by: Weng Meiling <wengmeiling.weng@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 0eae64c..63740da 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -993,14 +993,19 @@
i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
capability is set.
- i915.invert_brightness
+ i915.invert_brightness=
[DRM] Invert the sense of the variable that is used to
set the brightness of the panel backlight. Normally a
- value of 0 indicates backlight switched off, and the
- maximum value sets the backlight to maximum brightness.
- If this parameter is specified, a value of 0 sets the
- backlight to maximum brightness, and the maximum value
- switches the backlight off.
+ brightness value of 0 indicates backlight switched off,
+ and the maximum of the brightness value sets the backlight
+ to maximum brightness. If this parameter is set to 0
+ (default) and the machine requires it, or this parameter
+ is set to 1, a brightness value of 0 sets the backlight
+ to maximum brightness, and the maximum of the brightness
+ value switches the backlight off.
+ -1 -- never invert brightness
+ 0 -- machine default
+ 1 -- force brightness inversion
icn= [HW,ISDN]
Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]