[meta-intel] Intel Atom E3845: Backlight control
Cheah, Vincent Beng Keat
vincent.beng.keat.cheah at intel.com
Wed Nov 25 22:29:01 PST 2015
+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 --> /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> [mailto: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<mailto: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
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