Re: [PATCH] Documentation: Add entry for dell-laptop sysfs interface

On Friday 09 January 2015 22:57:14 Darren Hart wrote:

On Wed, Dec 31, 2014 at 12:20:59PM +0100, Gabriele Mazzotta wrote:

quoted

On Tuesday 30 December 2014 21:31:49 Brian Norris wrote:

quoted

Hi,

On Wed, Dec 03, 2014 at 06:41:33PM +0100, Gabriele Mazzotta wrote:

quoted

Add the documentation for the new sysfs interface of dell-laptop
that allows to configure the keyboard illumination on Dell systems.

Signed-off-by: Gabriele Mazzotta <redacted>
Signed-off-by: Pali Rohár <redacted>
---
 .../ABI/testing/sysfs-platform-dell-laptop         | 60 ++++++++++++++++++++++
 1 file changed, 60 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-platform-dell-laptop

diff --git a/Documentation/ABI/testing/sysfs-platform-dell-laptop b/Documentation/ABI/testing/sysfs-platform-dell-laptop
new file mode 100644
index 0000000..7969443
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-platform-dell-laptop

@@ -0,0 +1,60 @@
+What:		/sys/class/leds/dell::kbd_backlight/als_setting
+Date:		December 2014
+KernelVersion:	3.19
+Contact:	Gabriele Mazzotta <gabriele.mzt-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
+		Pali Rohár <pali.rohar-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
+Description:
+		This file allows to control the automatic keyboard
+		illumination mode on some systems that have an ambient
+		light sensor. Write 1 to this file to enable the auto
+		mode, 0 to disable it.

[...]

This entry appears wrong, or at least incomplete. My system boots with a
default value of 18, and the 'set' implementation accepts any value from
0 to 255.

According to the comments in dell-laptop.c, the value actually means
something different than on/off:

  cbArg3, byte0  Desired setting of ALS value that turns the light on or off.

Admittedly, I'm not clear on what the intended interface is, as I've
never had the ALS / keyboard backlight controls all working properly on
my laptop in the first place, but I thought this would be the right
place to ask about getting the documentation and driver in sync.

Hi,

You are perfectly right, the documentation is wrong and I'm sorry for
that. als_setting should allow you to define when the keyboard
backlight has to be turned on or off depending on the value reported
by the ambient light sensor.

Please note that not everything that is in libsmbios [1] is implemented
in the kernel driver. Take a look at it, recently there have been few
changes related to the ALS settings. Probably they are not needed given
that you are able to set the threshold with the current kernel driver,
but you might find something interesting.

I'll submit a patch to correct the documentation, thanks for reporting.

Hi Gabriele,

Have I missed a patch from you for this? I'd like to see this corrected in the
3.19 rc cycle.

Thanks,

I'm sorry, I must have done something wrong when I sent the patch, the
CC list is not complete.

Thanks for the link Brian.