Problem with brightness control on Toshiba Satellite R830 [SOLVED]

Question

Ever since I've been using Linux on my Toshiba Satellite R830 laptop I had problems with the brightness setting after wakeup from sleep. The solution I had found was to use a custom xorg.conf setup. Actually I was creating a 20-intel.conf file in /usr/share/X11/xorg.conf.d/ with the following content:
Section "Device"
Identifier "card0"
Driver "intel"
Option "Backlight" "intel_backlight"
BusID "PCI:0:2:0"
EndSection
This worked until today. Now I realised that Xorg is somewhat ignoring this configuration file. I looked in the wiki and this suggested that any such config files should be in /etc/X11/xorg.conf.d/. I copied the file there and rebooted. I opened a terminal and checked the value of /sys/class/backlight/intel_backlight/actual_brightness. Modified the brightness with the Fn + F6/F7 and checked again and it was controlling these.
But after closing the lid and leaving it for a while, and wakeing up the PC the Fn +F6/F7 keys started controlling /sys/class/backlight/toshiba/ which never worked after sleep. Somehow on wakeup the custom config files are being ignored. It seems this is related to the upgrade to Gnome 3.16. I'm using linux-lts kernel.
How do I make Xorg use intel_backlight instead of Toshiba for brightness control?
Last edited by entodoays (2015-05-18 15:21:04)

Answer 1

It seems that the culprit is /usr/lib/gnome-settings-daemon/gsd-backlight-helper. In this page: http://ubuntuforums.org/showthread.php?p=11910629 there's a procedure to patch the source file (for an older version). There's a section of the code like this:
/* available kernel interfaces in priority order */
static const gchar *backlight_interfaces[] = {
"nv_backlight",
"asus_laptop",
"toshiba",
"eeepc",
"thinkpad_screen",
"acpi_video1",
"mbp_backlight",
"acpi_video0",
"fujitsu-laptop",
"nvidia_backlight",
"samsung",
NULL,
Patching this file, eliminating the toshiba device from the preferred list and adding intel_backlight to it might solve the issue.
On another page, https://github.com/mate-desktop/mate-po … issues/135 they suggest another possible hack: changing the priority of device type
file plugins/power/gsd-backlight-helper.c
/* search the backlight devices and prefer the types:
* firmware -> platform -> raw */
path = gsd_backlight_helper_get_type (devices, "firmware");
if (path != NULL)
goto out;
path = gsd_backlight_helper_get_type (devices, "platform");
if (path != NULL)
goto out;
path = gsd_backlight_helper_get_type (devices, "raw");
if (path != NULL)
goto out;
Changing the order to firmware -> raw -> platform would solve the problem for me too.
Unfortunately I've never done any patching yet. How would I go about it?
Last edited by entodoays (2015-05-12 07:22:06)