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authorMatthew Garrett <mjg@redhat.com>2011-03-22 16:30:21 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2011-03-22 17:43:59 -0700
commitbb7ca747f8d6243b3943c5b133048652020f4a50 (patch)
treeb40e879a7b26e3763aea2af2d4dd9079483de11e /Documentation
parentccd7510fd8dea5b4b2af87fb2aef2ebd6b23b76b (diff)
downloadlinux-bb7ca747f8d6243b3943c5b133048652020f4a50.tar.bz2
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 <mjg@redhat.com> Cc: Richard Purdie <rpurdie@rpsys.net> Cc: Chris Wilson <chris@chris-wilson.co.uk> Cc: David Airlie <airlied@linux.ie> Cc: Alex Deucher <alexdeucher@gmail.com> Cc: Ben Skeggs <bskeggs@redhat.com> Cc: Zhang Rui <rui.zhang@intel.com> Cc: Len Brown <lenb@kernel.org> Cc: Jesse Barnes <jbarnes@virtuousgeek.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/ABI/stable/sysfs-class-backlight20
1 files changed, 20 insertions, 0 deletions
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 <rpurdie@rpsys.net>
Description:
Maximum brightness for <backlight>.
Users: HAL
+
+What: /sys/class/backlight/<backlight>/type
+Date: September 2010
+KernelVersion: 2.6.37
+Contact: Matthew Garrett <mjg@redhat.com>
+Description:
+ The type of interface controlled by <backlight>.
+ "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.