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Liberis

Member

Registered: 2012-11-11

Posts: 8

[SOLVED]intel_backlight service does not set backlight at boot

Hi everyone,

I have a Dell inspiron 3542 laptop.The problem is that even though the backlight.service saves and loads the backlight value it does not set it.For example:

 xbacklight -get 

outputs the saved backlight value but on screen it appears around 1-5% and only when i change it,it goes back to normal.According to systemd-backlight@.service manpage"if udev property ID_BACKLIGHT_CLAMP is not set to false value, the brightness is clamped to a value of at least 1 or 5% of maximum brightness, whichever is greater. This restriction will be removed when the kernel allows user space to reliably set  a brightness value which does not turn off the display."

My Question is how can i set the udev property

Thank you for any suggestions

Last edited by Liberis (2015-05-11 00:49:08)

Liberis

Member

Registered: 2012-11-11

Posts: 8

Re: [SOLVED]intel_backlight service does not set backlight at boot

I have to admit that the problem and the question was not well stated.I wanted to override backlight clamping because i thought that was the problem.
Ill try to post the solution as clear as i can (my english knowledge is not the best) .
The laptop im using has hybrid graphics(nvidia and intel) im using the open source drivers with i915 and nouveau modules and im using lvm2 dm-crypt setup

I tried the following

Recompiling systemd trying to revert this patch :https://github.com/systemd/systemd/comm … ca6c595c76

Setting -no-clamp option (could not make it right i think) in systemd-backlight@.service with(could not make it work i think i did not do it correct)
as stated at http://lists.freedesktop.org/archives/s … 27138.html

 systemctl edit systemd-backlight@.service 

[Service]
ExecStart=
ExecStop=
ExecStart=/usr/lib/systemd/systemd-backlight -no-clamp load %i
ExecStop=/usr/lib/systemd/systemd-backlight -no-clamp save %i

I could not find a way to set ID_BACKLIGHT_CLAMP in udev properties i did not quite understand what it was asking to be honest.

Solution

EDIT:1 Adding ENV{ID_BACKLIGHT_CLAMP}="0" in backlight section in /usr/lib/udev/rules.d/99-systemd.rules also solves the issue as the man page says.

Do not judge these might were completely wrong moves but with little to no knowledge only trial and error could help

I  could also set the saved backlight at boot by blacklisting the i915 module and leaving nouveau.
The strange thing is that i915 is still being  loaded while using PRIME

glxinfo | grep "OpenGL renderer"
OpenGL renderer string: Mesa DRI Intel(R) Haswell Mobile

and the lsmod output

 lsmod | grep i915
i915                 1024000  4 
intel_gtt              20480  1 i915
drm_kms_helper        102400  2 i915,nouveau
drm                   282624  8 ttm,i915,drm_kms_helper,nouveau
i2c_algo_bit           16384  2 i915,nouveau
video                  24576  2 i915,nouveau
button                 16384  2 i915,nouveau
i2c_core               53248  10 drm,i915,i2c_i801,i2c_hid,i2c_designware_platform,drm_kms_helper,i2c_algo_bit,v4l2_common,nouveau,videodev

also journalctl -xe output

-- Unit systemd-backlight@backlight:intel_backlight.service has begun starting up.
May 11 02:43:20 archlinux kernel: ACPI: Video Device [GFX0] (multi-head: yes  rom: no  post: no)
May 11 02:43:20 archlinux kernel: input: Video Bus as /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/LNXVIDEO:01/input/input11
May 11 02:43:20 archlinux kernel: snd_hda_intel 0000:00:03.0: bound 0000:00:02.0 (ops i915_audio_component_bind_ops [i915])
May 11 02:43:20 archlinux kernel: [drm] Initialized i915 1.6.0 20150130 for 0000:00:02.0 on minor 1
May 11 02:43:20 archlinux kernel: [drm:hsw_unclaimed_reg_detect.isra.10 [i915]] *ERROR* Unclaimed register detected. Please use the i915.mmio_debug=1 to debug this proble
May 11 02:43:20 archlinux kernel: input: HDA Digital PCBeep as /devices/pci0000:00/0000:00:1b.0/sound/card1/hdaudioC1D0/input9
May 11 02:43:20 archlinux kernel: input: HDA Intel PCH Headphone Mic as /devices/pci0000:00/0000:00:1b.0/sound/card1/input12
May 11 02:43:20 archlinux kernel: Console: switching to colour frame buffer device 170x48
May 11 02:43:20 archlinux kernel: i915 0000:00:02.0: fb0: inteldrmfb frame buffer device
May 11 02:43:20 archlinux kernel: i915 0000:00:02.0: registered panic notifier
May 11 02:43:20 archlinux systemd[1]: Found device ST1000LM024_HN-M101MBB sda1.
-- Subject: Unit dev-disk-by\x2duuid-7D28\x2d5BEB.device has finished start-up
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
-- -- -- 


-- The start-up result is done.
May 11 02:43:20 archlinux systemd[1]: Started Load/Save Screen Backlight Brightness of backlight:intel_backlight.
-- Subject: Unit systemd-backlight@backlight:intel_backlight.service has finished start-up
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
-- 
-- Unit systemd-backlight@backlight:intel_backlight.service has finished starting up.
-- 

EDIT:2 Avoided the blacklisting by setting nouveau early KMS to boot earlier at mkinitcpio.conf and the result is the same
I think nouveau has to be loaded before i915 otherwise intel_backlight service is not working even though

 systemctl status systemd-backlight@intel_backlight.service  

shows no errors

I have to say that i have not quite understood why this is working like this but i would love if anyone can explain it.
i can provide more info if needed

Last edited by Liberis (2015-05-12 00:51:38)