Red Hat Bugzilla – Bug 590780
thinkpad W701 backlight control nonfunctional
Last modified: 2013-10-20 18:43:28 EDT
Created attachment 412908 [details]
acpidump from W701
Description of problem:
Thinkpad W701 backlight controls do not work. Neither the hotkeys nor gnome-power-manager controls work.
acpi_listen indicates the hotkeys are being registered.
/sys/class/backlight for this notebook shows three interfaces:
Of the three, /sys/class/backlight/acpi_video0 is nonfunctional; though populated, the values are suspect and writing to /sys/class/backlight/acpi_video0/brightness has no effect whatsoever.
/sys/class/backlight/thinkpad_screen/brightness is partly functional, but the adjustment range is incorrect and the interface stops working entirely after the first suspend/hibernate.
The interface entries found in /sys/class/backlight/nv_backlight are 100% functional with a correct full range, and work through suspend/hibernate cycles. It doesn't appear anything is trying to use this interface.
Version-Release number of selected component (if applicable):
Fedora 13 Beta, 18.104.22.168-85.fc13.x86_64 kernel, standard graphical boot with plymouth/Nouveau
Steps to Reproduce:
1. Install Fedora 13 Beta on a Thinkpad W510 or W701
2. Attempt to use backlight controls
g-p-m OSD pops, but bargraph does not move. Backlight brightness remains unaltered from boot.
Backlight dims/brightens according to input. OSD reflects screen brightness changes.
acpidump attached for W701 25003BU with BIOS 1.03-1.10
Note that the /sys/class/backlight/thinkpad_screen interface appears to work until first suspend, however it can neither fully dim nor fully brighten the screen. It becomes completely nonfunctional after waking from suspend. Windows 7 users on the Lenovo forums are complaining about an identical bug; this interface is broken in the BIOS?
nevertheless the /sys/class/backlight/nv_backlight interface works 100% properly.
Created attachment 412911 [details]
dmesg dump from a clean boot W701
Repeating my test steps more carefully with mjg, the acpi_video0 interface *is* working properly. It has both the correct range declared and the brightness entry responds correctly. I'm not sure how I screwed up the original test (actually I think I do know-- errant boot param), but check and double-check shows that /sys/class/backlight/acpi_video0 *is* functioning properly in a completely normal boot with and without rhgb/nouveau/plymouth.
However,the hotkeys still pop an OSD that does not respond and does not change brightness. The hotkeys also do not work from VTs.
Created attachment 412917 [details]
gnome-power-mnaager --verbose dump
Another amendment-- the acpi_video0 interface does *not* work after suspend :-(
The hotkeys work, the OSD bargraph moves up and down, but the brightness does not change. the nv_backlight interface *does* still work.
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