From bb7ca747f8d6243b3943c5b133048652020f4a50 Mon Sep 17 00:00:00 2001 From: Matthew Garrett Date: Tue, 22 Mar 2011 16:30:21 -0700 Subject: backlight: add backlight type There may be multiple ways of controlling the backlight on a given machine. Allow drivers to expose the type of interface they are providing, making it possible for userspace to make appropriate policy decisions. Signed-off-by: Matthew Garrett Cc: Richard Purdie Cc: Chris Wilson Cc: David Airlie Cc: Alex Deucher Cc: Ben Skeggs Cc: Zhang Rui Cc: Len Brown Cc: Jesse Barnes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/ABI/stable/sysfs-class-backlight | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) (limited to 'Documentation') diff --git a/Documentation/ABI/stable/sysfs-class-backlight b/Documentation/ABI/stable/sysfs-class-backlight index 4d637e1c4ff7..70302f370e7e 100644 --- a/Documentation/ABI/stable/sysfs-class-backlight +++ b/Documentation/ABI/stable/sysfs-class-backlight @@ -34,3 +34,23 @@ Contact: Richard Purdie Description: Maximum brightness for . Users: HAL + +What: /sys/class/backlight//type +Date: September 2010 +KernelVersion: 2.6.37 +Contact: Matthew Garrett +Description: + The type of interface controlled by . + "firmware": The driver uses a standard firmware interface + "platform": The driver uses a platform-specific interface + "raw": The driver controls hardware registers directly + + In the general case, when multiple backlight + interfaces are available for a single device, firmware + control should be preferred to platform control should + be preferred to raw control. Using a firmware + interface reduces the probability of confusion with + the hardware and the OS independently updating the + backlight state. Platform interfaces are mostly a + holdover from pre-standardisation of firmware + interfaces. -- cgit v1.2.3