[meta-intel] Intel Atom E3845: Backlight control

[Prasant J]

On Thu, Nov 26, 2015 at 5:14 PM, Adebisi, YetundeX <
yetundex.adebisi at intel.com> wrote:

> Hi,
>
>
>
> If  the i915 driver is being used then the sysfs option should be
> /sys/class/backlight/intel_backlight/brightness. If the intel_backlight
> path is not present, then the best thing is to enable debug by adding drm.debug
> =0xe to the kernel command line as Vincent suggested to see what is going
> on.
>
>
>
> Regards,
>
>
>
> Yetunde
>
>
>
> *From:* Cheah, Vincent Beng Keat
> *Sent:* Thursday, November 26, 2015 6:29 AM
> *To:* Chang, Rebecca Swee Fun; Prasant J; Ahmad, Mohd Azril; Adebisi,
> YetundeX
>
> *Cc:* meta-intel at yoctoproject.org
> *Subject:* RE: [meta-intel] Intel Atom E3845: Backlight control
>
>
>
> +Yetunde.
>
>
>
> Hi PJ,
>
>
>
> I don’t think we have tried the xrandr option to do backlight but I
> believe you should be able to control LVDS backlight simply by accessing
> this sysfs à  /sys/class/backlight/acpi_video0/brightness  (hmm…  this
> looks pretty much like what you have done below – referring to the PCI
> path).  Could you please add drm.debug =0xe to enable DRM debug to see what
> is going on down there. Also, it would definitely be nice if you can make
> your image in run-level-3 to isolate the user-space from the kernel side
> when you are testing this.
>
>
>
> URL:
>
> https://wiki.archlinux.org/index.php/Backlight
>
>
>
> … Vincent
>
>
>
> *From:* Chang, Rebecca Swee Fun
> *Sent:* Thursday, November 26, 2015 8:41 AM
> *To:* Prasant J <pj0585 at gmail.com>; Cheah, Vincent Beng Keat <
> vincent.beng.keat.cheah at intel.com>; Ahmad, Mohd Azril <
> mohd.azril.ahmad at intel.com>
> *Cc:* meta-intel at yoctoproject.org
> *Subject:* RE: [meta-intel] Intel Atom E3845: Backlight control
>
>
>
> Hi Vincent/ Azril,
>
>
>
> Can you help to provide advice to Pj?
>
> Thanks.
>
>
>
> Regards,
>
> Rebecca
>
>
>
> *From:* meta-intel-bounces at yoctoproject.org [
> mailto:meta-intel-bounces at yoctoproject.org
> <meta-intel-bounces at yoctoproject.org>] *On Behalf Of *Prasant J
> *Sent:* Wednesday, November 25, 2015 8:46 PM
> *To:* meta-intel at yoctoproject.org
> *Subject:* [meta-intel] Intel Atom E3845: Backlight control
>
>
>
> Hi,
>
> I'm using Intel Atom E3845 with my custom hardware. I have an LVDS display
> and I would like to control the brightness from the linux shell.
>
> I used the command:
>
> xrandr --output DP2 --brightness <val>
>
> This command (I think) changes the gamma factor of the display but the
> actual back light intensity is not changed.
>
> I tried changing the value of:
> /sys/devices/pci0000:00/0000:00:02.0/backlight/acpi_video0/brightness
>
> but still no change in the back light intensity.
>
>
>
> Any inputs on how can I control the back light intensity of my LVDS
> display?
>
>
>
> Regards, Pj
>
>
>
Hi Rebecca, Vincent, Yetunde,


Thanks for your inputs on my query & sorry for my late response.


I got in touch with my hardware vendor on this topic and it turns out that
I have not installed certain kernel modules that they provide. Those
modules provide back light control.


Thanks once again!


Regards, Pj
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