backlight: lm3639: document sysfs attributes

Add documentation for sysfs interfaces of Texas Instruments lm3639
backlight + flash led driver chip by looking through git commits and
reading code.

Signed-off-by: Aishwarya Pant <aishpant@gmail.com>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

diff --git a/Documentation/ABI/testing/sysfs-class-backlight-lm3639 b/Documentation/ABI/testing/sysfs-class-backlight-lm3639
new file mode 100644 (file)
index 0000000..f7e92a8
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-backlight-lm3639
@@ -0,0 +1,11 @@
+sysfs interface for Texas Instruments lm3639 backlight + flash led driver chip
+------------------------------------------------------------------------------
+
+What:          /sys/class/backlight/<backlight>/bled_mode
+Date:          Oct, 2012
+KernelVersion: v3.10
+Contact:       dri-devel@lists.freedesktop.org
+Description:
+               (WO) Write to the backlight mapping mode. The backlight current
+               can be mapped for either exponential (value "0") or linear
+               mapping modes (default).