Bugzilla – Bug 297155
Brightness control /proc/acpi/ibm/brightness: not using full range
Last modified: 2007-09-12 09:09:41 UTC
This is with a few-days old Factory. I have a Thinpad R61 (should be the same hardware as a T61). If I change the brightness using kpowersave or directly via /proc/acpi/ibm/brightness I can only reach half of the total range. Starting from level 0 and minimal brightness using [Fn]+[bright v]: echo level 7 > /proc/acpi/ibm/brightness gives only half of the maximal brightness. Analogously, starting from level 7 plus [Fn]+[bright ^], going to level 0 reduces also the brightness to half and not to the minimal possible value. Also, if one presses [Fn]+[bright ^/v], the level jumps from 7 to 1/0 [alternating] to 1 to 0 and from 0 to 6/7 to 7. (Actually, some values in between are shown, if one outputs /proc/acpi/ibm/brightness every 0.1s: "0 ... 0 1 2 3 4 5 6 7 6 7 6 7 ...). I don't know which hwinfo --<???> or similar info is needed.
a small comment: you should use sysfs to change the brightness and no longer the proc interface.
(In reply to comment #1 from Danny Kukawka) > a small comment: you should use sysfs to change the brightness and no longer > the proc interface. Actually, I usually simply use the Fn+brighter/darker buttons, which works (8 brightness steps); otherwise I want that kpowersave works. In terms of sysfs I have: /sys/class/backlight/thinkpad_screen/ brightness/actual_brightness (0 to 7, same problems as described above) max_brightness (always 7) /sys/class/backlight/acpi_video0/ actual_brightness brightness max_brightness: always 100 /sys/class/backlight/acpi_video1/ actual_brightness between 20 and 100 - this value actually seems to work -- I get 8 different % values. brightness - remains at 100 [I'm using the Fn-brightness buttons] max_brightness (is 100) Using "echo 50 > brightness", I often end up with actual_brightness = 20; I have to use the command once or twice again to get the desired value. Why does acpi_video1 work and thinkpad_screen does not?
I think there is a bug in the kernel. IMO we should no load the video module by default on Thinkpads. /sys/class/backlight/thinkpad_screen/ should do the job.
Beta2 will fix the acpi_video bug. You can work around it this way: echo "install video /bin/true" > /etc/modprobe.d/intel-i810-xorg-x11
Can you still reproduce this bug with beta3?
(In reply to comment #5 from Christopher Stender) > Can you still reproduce this bug with beta3? I still have the same problem: Using Fn+brightness I can change the brightness in 15 (new!) steps, using e.g. kpowersave, only a limited brightness range is accessible.
Can you change the brightness level step by step with via the /sys interface? What does "cat /sys/class/backlight/thinkpad_screen/actual_brightness" say if you're on max / min brightness level?
I pressed Fn-darker until I reached maximal darkness; And now: $ cd /sys/class/backlight/thinkpad_screen/ $ cat actual_brightness 0 # press now "Fn+brighter" and cat then actual_brightness: 1 # ditto 2 3 4 5 6 7 0 # screen is brighter, but number wrapped around. 1 2 3 4 5 6 7 # maximal brightness after 15 times pressing "Fn+brighter" Depending in which half I am, the brightness "7" goes either to the middle or to the brightness; and "0" goes to the middle or to the lowest brightness.
(remove needs info)
IMO a duplicate of bug #308264
Yes, I also think so. Tobias, can you please post your last comment with a few more information to bug #308264? I'll close this bug as a duplicate of it.
In principle as 297155 < 308264 it should be the other way round ;-) I marked this bug as duplicate of bug 308264 and will add a comment there. *** This bug has been marked as a duplicate of bug 308264 ***
Yes, you're right. Normally I would mark bug 308264 as a duplicate, but in this case, there are more information in bug 308264. Next time you will win :)