brightness control stopped working after update to linux-2.6.27-11-generic kernel

[rupert angermeier]

after upgrading to 2.6.27-11-generic (on intrepid) changing the display brightness stopped working on several thinkpad models (x61t, t60 and t500 are mentioned at http://ubuntuforums.org/showthread.php?t=1054247, i use a x61)

when i use the brightness controls the gnome-brightness-bar (or whatever this onscreen indicator is called) pops up and reflects some change, however the displays brightness won't change. same goes for xbacklight or the gnome-brightness-applet.

i guess theses were the relevant changes which caused this bug: (from http://launchpadlibrarian.net/20551423/linux_2.6.27-10.20_2.6.27-11.21.diff.gz )

--- linux-2.6.27.orig/drivers/misc/thinkpad_acpi.c
+++ linux-2.6.27/drivers/misc/thinkpad_acpi.c
@@ -4921,16 +4921,25 @@
   */
  b = tpacpi_check_std_acpi_brightness_support();
  if (b > 0) {
- if (thinkpad_id.vendor == PCI_VENDOR_ID_LENOVO) {
- printk(TPACPI_NOTICE
- "Lenovo BIOS switched to ACPI backlight "
- "control mode\n");
- }
- if (brightness_enable > 1) {
- printk(TPACPI_NOTICE
- "standard ACPI backlight interface "
- "available, not loading native one...\n");
- return 1;
+
+ if (acpi_video_backlight_support()) {
+ if (brightness_enable > 1) {
+ printk(TPACPI_NOTICE
+ "Standard ACPI backlight interface "
+ "available, not loading native one.\n");
+ return 1;
+ } else if (brightness_enable == 1) {
+ printk(TPACPI_NOTICE
+ "Backlight control force enabled, even if standard "
+ "ACPI backlight interface is available\n");
+ }
+ } else {
+ if (brightness_enable > 1) {
+ printk(TPACPI_NOTICE
+ "Standard ACPI backlight interface not "
+ "available, thinkpad_acpi native "
+ "brightness control enabled\n");
+ }
   }
  }

ProblemType: Bug
Architecture: amd64
DistroRelease: Ubuntu 8.10
Package: linux-image-2.6.27-11-generic 2.6.27-11.27
ProcCmdLine: root=UUID=0aaf3329-a880-44fe-a562-92152a53fff0 ro acpi_sleep=s3_bios quiet splash locale=de_DE
ProcEnviron:
 PATH=/home/username/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games
 LANG=de_AT.UTF-8
 SHELL=/bin/bash
ProcVersionSignature: Ubuntu 2.6.27-11.27-generic
SourcePackage: linux

[Román (faneca)]

Its a bit off-topic, but for my Dell Inspiron laptop, the upgrade has brought the correct behaviour for my brightness keys back, something that had not happened since 7.04 (light changed four times in a row each time one of those keys where pressed). Just wanted to mention that to ask the developers to be a little carefull when solving your problem ;-). Good luck with it!