Red Hat Bugzilla – Bug 677694
/sys/class/backlight/nv_backlight/max_brightness is set to lower value after suspend on battery power giving dim display
Last modified: 2011-02-21 07:02:38 EST
Created attachment 478899 [details]
lspci -vv -nn -d 10de:0a29
Description of problem:
On boot with updated Rawhide on Samsung R590 laptop (Nvidea GM330) /sys/class/backlight/nv_backlight/max_brightness is set to 1073864551
The brightness is fine for viewing and controllable via keys. If power cable is connected suspend/resume is ok and the brightness consistent.
However, when on battery power a resume comes back with a very dim display and max_brightness is set to 1025. Keys work for adjusting brightness but do not get more than very dim.
Attempting to exceed the now lower max_value results in:
echo 1026 > /sys/class/backlight/nv_backlight/brightness
-bash: echo: write error: Invalid argument
(attempted writing large value to max_brightness results in permission denied)
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. Boot, login.
2. Note /sys/class/backlight/nv_backlight/max_brightness is 1073864551.
3. Run on battery and suspend/resume. Note dimmed display and changed max_brightness value.
Display is dim. Brightness keys go to max but display is still too dark to use.
/sys/class/backlight/nv_backlight/max_brightness is set to 1025
Brightness returns to normal levels.
Possibly related to https://bugzilla.redhat.com/show_bug.cgi?id=625171
In which case it is the initial max_brightness value is incorrect (but which works).
Created attachment 478900 [details]
/var/log/messages excerpt after issue
Created attachment 478901 [details]
This has been fixed with latest updates.
/sys/class/backlight/acpi_video0/max_brightness is now 7
Removing power dims the screen but using keyboard it can be increased to 7.
/sys/class/backlight/nv_backlight is no longer present.