Bug 297155

Summary:	Brightness control /proc/acpi/ibm/brightness: not using full range
Product:	[openSUSE] openSUSE 10.3	Reporter:	Tobias Burnus <burnus>
Component:	Kernel	Assignee:	E-mail List <kernel-maintainers>
Status:	RESOLVED DUPLICATE	QA Contact:	E-mail List <qa-bugs>
Severity:	Minor
Priority:	P5 - None
Version:	Alpha 6
Target Milestone:	---
Hardware:	Other
OS:	Other
Whiteboard:
Found By:	---	Services Priority:
Business Priority:		Blocker:	---
Marketing QA Status:	---	IT Deployment:	---

Description Tobias Burnus 2007-08-03 09:49:33 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.

Comment 1 Danny Al-Gaaf 2007-08-13 17:51:29 UTC

a small comment: you should use sysfs to change the brightness and no longer the proc interface.

Comment 2 Tobias Burnus 2007-08-13 18:09:28 UTC

(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?

Comment 3 Danny Al-Gaaf 2007-08-13 18:19:50 UTC

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.

Comment 4 Christopher Stender 2007-08-13 18:27:21 UTC

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

Comment 5 Christopher Stender 2007-09-06 19:01:53 UTC

Can you still reproduce this bug with beta3?

Comment 6 Tobias Burnus 2007-09-11 09:58:40 UTC

(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.

Comment 7 Christopher Stender 2007-09-11 14:02:08 UTC

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?

Comment 8 Tobias Burnus 2007-09-11 14:14:15 UTC

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.

Comment 9 Tobias Burnus 2007-09-11 14:15:14 UTC

(remove needs info)

Comment 10 Danny Al-Gaaf 2007-09-11 14:21:13 UTC

IMO a duplicate of bug #308264

Comment 11 Christopher Stender 2007-09-11 20:09:49 UTC

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.

Comment 12 Tobias Burnus 2007-09-12 08:31:11 UTC

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 ***

Comment 13 Christopher Stender 2007-09-12 09:09:41 UTC

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 :)