Bug 43741 - /sys/class/backlight/ is empty with AMD (ATI) Radeon HD 4350
Summary: /sys/class/backlight/ is empty with AMD (ATI) Radeon HD 4350
Status: RESOLVED CODE_FIX
Alias: None
Product: Drivers
Classification: Unclassified
Component: Video(DRI - non Intel) (show other bugs)
Hardware: x86-64 Linux
: P1 normal
Assignee: drivers_video-dri
URL:
Keywords:
Depends on:
Blocks: 56331
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Reported: 2012-06-25 10:53 UTC by rpr.nospam
Modified: 2015-02-19 16:47 UTC (History)
4 users (show)

See Also:
Kernel Version: 3.2.0-26-generic
Subsystem:
Regression: No
Bisected commit-id:

Attachments
/var/log/dmesg (68.35 KB, text/plain)
2012-06-25 10:53 UTC, rpr.nospam 		Details
output of lsmod (2.87 KB, text/plain)
2012-06-25 10:54 UTC, rpr.nospam 		Details
output of 'sudo lspci -vvnn' (41.57 KB, text/plain)
2012-06-25 10:55 UTC, rpr.nospam 		Details
output of 'sudo acpidump' (152.90 KB, text/plain)
2012-06-25 10:56 UTC, rpr.nospam 		Details
Add an attachment (proposed patch, testcase, etc.)

Description rpr.nospam 2012-06-25 10:53:31 UTC 
Created attachment 74171 [details]
/var/log/dmesg

Hi!

On an Ubuntu 12.04 PC with Linux 3.2.0-26-generic x86_64 and
AMD (ATI) Radeon HD 4350 VGA controller the kernel does not recognize
the ability of the VGA to change brightness of the connected monitor
(HP LA2405wg).

/sys/class/backlight/ is empty and tools for brightness control report
errors. I tried the following options in /etc/default/grub (and
updated grub configuration after the change):

GRUB_CMDLINE_LINUX="pcie_aspm=force acpi_osi=Linux acpi_backlight=vendor"

but to no avail.

-- rpr.
Comment 1 rpr.nospam 2012-06-25 10:54:30 UTC 
Created attachment 74181 [details]
output of lsmod
Comment 2 rpr.nospam 2012-06-25 10:55:51 UTC 
Created attachment 74191 [details]
output of 'sudo lspci -vvnn'
Comment 3 rpr.nospam 2012-06-25 10:56:44 UTC 
Created attachment 74201 [details]
output of 'sudo acpidump'
Comment 4 Zhang Rui 2012-11-13 07:36:26 UTC 
there is no ACPI Backlight control on your laptop.
so sorry I can not help you on this.

re-assign to the graphics expert.
Comment 5 Alex Deucher 2012-11-13 13:27:11 UTC 
If your laptop uses the backlight controller on the GPU, there is support for it in kernel 3.7.
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