[Bug 12637] Re: LCD Brightness on Laptop Always Set Very Low at Boot

Alberto Emiliani elba at libero.it
Thu Sep 4 23:30:27 UTC 2008

I've found this page after some time I was fighting against this bug. Intrepid alpha5 should come in a few hours or perhaps minutes, but I describe my version of the bug in the meantime.
ASUS Z53H. Ubuntu Hardy 8.04. Kernel 2.6.24-21-generic -- to test the new Broadcom wireless drivers, but the bug was there before (
---The screen is dim on boot. I have to brighten it with Fn-F6. This function key is not active until the session begins. After typing username and password and waiting for Gnome to start, I can brighten the lcd with Fn key F6. I have to keep the key pressed for a while -- the slide has to climb all the way from minimum to maximum brightness (remember this). During the session, the screen gets dim on other occasions: when vlc reproduces a video (but not when it starts as a program, only after I select and file and vlc actually begins to reproduce it); when mplayer GUI _starts_ -- even before reproducing a video; when, after shifting to tty1 (CTRL-ALT-F1), I go back to Gnome (Alt-F7). In all these cases, I re-brighten the screen, but the brightness slide is already at its maximum -- this might have to do with the incongruence between actual and expected brightness. Thus, for _these_ kinds of dimming, pressing a fn-key once works, and I can also press Fn-F7 twice -- the screen is blanked and bright again; whereas, if I try Fn-F7 twice on boot, the screen blanks and turns _dim_ again. I don't know if this difference is meaningful.
Now, I report some weird behaviour of the bug and the testing I did, hoping that it may be useful for fixing the issue.
---I have GRUB and dual boot. (Must say I have booted WinXP only once during the last month -- fine.) On restart, after logging out of Ubuntu, also WinXP _starts_ with dim screen: I increase brightness, power off: when it restarts, it is bright from the beginning (tried only once). (It strikes me that it might be interesting to try not to brighten the screen while XP is on, power off, reboot and see if the screen is still dim even in XP. If you tell me to try this one, I'll do.) On the contrary, when I power off from Ubuntu, the screen is dim from the beginning: even GRUB has a dim display.
---The following may be interesting. I had to fix a cpu frequency scaling issue. Cpu freq scaling was not working, and I activated it by
$ modprobe acpi-cpufreq
I reconfigured the gnome applets and put a script in init.d to make the change permanent. I did update-rc.d etc. After that, all the dimming issue completely disappeared for a while. I mean: no trouble with VLC or mplayer, the boot was bright and so on. When the screen got dim because idle, touching the mouse set it back to bright -- for some ten days during which the pc was extensively used. Then, some days ago, the bug came back. I CANNOT exactly remember what I did, dammit. The session was suspended and resumed twice (I normally do not use suspend), some new software was installed, tried and uninstalled. When I realized the bug was back, I tried to remove my init.d file, to update-rc.d, to remove the module manually with modprobe, and then to reinstall it, but nothing worked. If this is really of some use to you, I can try to do everything from the beginning: reinstall Ubuntu, follow my steps as best as I can, and report. 
---Last (but it's getting quite late in the night in my part of the world and Alpha5 is still not there :-P). I tried to follow the behaviour of the system when the dimming occurs. First, I tried with acpi_listen, then I kept acpid log file monitored. That is, I tried to trigger the dimming and continually checked /var/log/acpid to see what was happening. When VLC loaded, nothing changed in ACPI: but as soon as the video reproduction started (and the screen became dim), I got:
    received event "hotkey ATKD 00000010 00000003"
    notified client 5470[111:123]
    notified client 5617[0:0]
    completed event "hotkey ATKD 00000010 00000003"
Then  I pressed Fn-F6, getting
    received event "video LCDD 00000086 00000000"
    notified client 5470[111:123]
    notified client 5617[0:0]
    exec action "/etc/acpi/video_brightnessup.sh"
    action exited with status 0
    completed event "video LCDD 00000086 00000000"
This is okay: predictable behaviour, since there is an explicit rule in /etc/acpi/events to handle events "video LCDD 00000086 00000000": but the block before about the hotkey ATKD might be interesting to investigate (I don't really know, I am a complete beginner in Linux and finding the info is a bit laborious at this level).
Then I launch mplayer and, as soon as the program starts (the screen dims) I get:
    received event "hotkey ATKD 00000010 00000004"
    notified client 5470[111:123]
    notified client 5617[0:0]
    completed event "hotkey ATKD 00000010 00000004"
That is, another ACPI event of kind "hotkey ATKD 00000010" -- this is a 04, not a 03. No events like these are present in the ACPI rules in /etc/acpi/events (I have checked with grep). I wonder what such events might be -- some googling did not give me any results.
OK -- sorry for having been so verbose -- this is because I cannot really tell what may be relevant for you.
I should like to learn how to compile my kernel -- this is in the agenda; but I am afraid this will not be tonight. So -- best wishes, and I'll tell you something more as soon as I try the new live CD!!

LCD Brightness on Laptop Always Set Very Low at Boot
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