[SOLVED] After xorg-server update backlight is not behaving

Question

After updating a Thinkpad S540 today the system goes into dim backlight level for the screen during the initial stages of the boot process, and recovers to normal brightness after the password has been entered in the KDM greeter and the user logs in to KDE. Running KDE the brightness behaves normally, but when the system shuts down after logging out from KDE the text output during shutdown does into very dim mode again.
The brightness parameters when logged in to KDE look fine.
$ ls -1 /sys/class/backlight/intel_backlight/*brightness | xargs -I % sh -c "echo % ; cat %"
/sys/class/backlight/intel_backlight/actual_brightness
937
/sys/class/backlight/intel_backlight/brightness
937
/sys/class/backlight/intel_backlight/max_brightness
937
$ ls -1 /sys/class/backlight/acpi_video0/*brightness | xargs -I % sh -c "echo % ; cat %"
/sys/class/backlight/acpi_video0/actual_brightness
100
/sys/class/backlight/acpi_video0/brightness
100
/sys/class/backlight/acpi_video0/max_brightness
100
The snippet of journal log relevant to the brightness setting is:
Jul 29 17:56:28 lenovo1 systemd[1]: Created slice system-systemd\x2dbacklight.slice.
Jul 29 17:56:28 lenovo1 systemd[1]: Starting Load/Save Screen Backlight Brightness of backlight:acpi_video0...
Jul 29 17:56:28 lenovo1 kernel: thinkpad_acpi: ThinkPad ACPI Extras v0.25
Jul 29 17:56:28 lenovo1 kernel: thinkpad_acpi: http://ibm-acpi.sf.net/
Jul 29 17:56:28 lenovo1 kernel: thinkpad_acpi: ThinkPad BIOS GPET58WW (1.58 ), EC unknown
Jul 29 17:56:28 lenovo1 kernel: thinkpad_acpi: Lenovo ThinkPad S5-S540, model 20B3CTO1WW
Jul 29 17:56:28 lenovo1 systemd[1]: Starting Load/Save Screen Backlight Brightness of backlight:intel_backlight...
Jul 29 17:56:28 lenovo1 kernel: snd_hda_intel 0000:00:1b.0: irq 61 for MSI/MSI-X
Jul 29 17:56:28 lenovo1 kernel: tpm_tis 00:0b: 1.2 TPM (device-id 0x0, rev-id 78)
Jul 29 17:56:28 lenovo1 kernel: ACPI Error: [\_SB_.PCI0.GFX0.DD02._BCL] Namespace lookup failure, AE_NOT_FOUND (20
Jul 29 17:56:28 lenovo1 kernel: ACPI Error: Method parse/execution failed [\_SB_.PCI0.RP05.PEGP.DD02._BCL] (Node f
Jul 29 17:56:28 lenovo1 kernel: thinkpad_acpi: detected a 8-level brightness capable ThinkPad
Jul 29 17:56:28 lenovo1 kernel: thinkpad_acpi: This ThinkPad has standard ACPI backlight brightness control, suppo
Jul 29 17:56:28 lenovo1 kernel: thinkpad_acpi: Disabling thinkpad-acpi brightness events by default...
Jul 29 17:56:28 lenovo1 systemd-backlight[200]: Saved brightness 11 too low; increasing to 46.
Jul 29 17:56:28 lenovo1 kernel: snd_hda_intel 0000:00:03.0: irq 62 for MSI/MSI-X
Jul 29 17:56:28 lenovo1 kernel: ACPI Exception: AE_BAD_PARAMETER, Returned by Handler for [EmbeddedControl] (20140
Jul 29 17:56:28 lenovo1 kernel: ACPI Error: Method parse/execution failed [\_TZ_.TZ01._TMP] (Node ffff880226839cd0
Jul 29 17:56:28 lenovo1 kernel: ACPI Exception: AE_BAD_PARAMETER, Returned by Handler for [EmbeddedControl] (20140
Jul 29 17:56:28 lenovo1 kernel: ACPI Error: Method parse/execution failed [\_TZ_.TZ01._TMP] (Node ffff880226839cd0
Jul 29 17:56:28 lenovo1 systemd[1]: Started Load/Save Screen Backlight Brightness of backlight:acpi_video0.
Jul 29 17:56:28 lenovo1 systemd[1]: Started Load/Save Screen Backlight Brightness of backlight:intel_backlight.
Booting with kernel parameter systemd.restore_state=0 gives a normal brightness throughout. So this must have something to do with the saving of the brightness parameters by systemd. The clue is in the journal log above:
systemd-backlight[200]: Saved brightness 11 too low; increasing to 46.
I wonder how I can get systemd to reset the stored value which is too low to be sensible?
Has anyone seen similar behaviour and if so is there a proper fix instead of the workaround in the bug I have filed upstream as below?
Filed arch bug https://bugs.archlinux.org/task/41390
and upstream at https://bugs.freedesktop.org/show_bug.cgi?id=81884
Last edited by mcloaked (2014-08-13 08:58:01)

Answer 1

@iskandr , @ens  about backlight and fn keys:
keys work (I checked by xmodmap) and backlight control works, but only by:
/sys/class/backlight/intel_backlight/brightness
old scripts which used for example:
/sys/class/backlight/acpi_video0/brightness
stopped works.
I wonder if this is a BUG or new feature? Where are handlers in clean Linux / systemd responsible for action to acpi keys which controlls backlight? ( I checked and it's not acpid /etc/acpi/handler.sh - acpi keys backlight controll works without it ). (moreover,acpid is external application as well as xbacklight, gbacklight etc... It should work OOTB, without these applications and also in the console.)
to turn on old interface as before 3.16 try add
video.use_native_backlight=0
to GRUB_CMDLINE_LINUX_DEFAULT line in /etc/default/grub  ( remember about grub-mkconfig -o /boot/grub/grub.cfg )
it turns on old interface:
ls -l /sys/class/backlight/
lrwxrwxrwx 1 root root 0 08-15 13:36 acpi_video0 -> ../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/backlight/acpi_video0
lrwxrwxrwx 1 root root 0 08-15 13:36 acpi_video1 -> ../../devices/pci0000:00/0000:00:02.0/backlight/acpi_video1
lrwxrwxrwx 1 root root 0 08-15 13:36 intel_backlight -> ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-LVDS-1/intel_backlight
and everything works again as before 3.16.
http://cgit.freedesktop.org/xorg/driver … 0d681c171e
This is another BUG (also occurs to my laptop). I see that the code is ready, so wait for a fix update.
I wonder also whether and where to file a bug report (about fn keys + backlight control).
Last edited by kelloco2 (2014-08-15 12:38:16)