Bug 48941 - Error creating '/sys/class/backlight/radeon_bl' in radeon_atom_backlight_init()
Summary: Error creating '/sys/class/backlight/radeon_bl' in radeon_atom_backlight_init()
Status: RESOLVED CODE_FIX
Alias: None
Product: Drivers
Classification: Unclassified
Component: Video(DRI - non Intel) (show other bugs)
Hardware: All Linux
: P1 normal
Assignee: drivers_video-dri
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2012-10-17 00:34 UTC by Igor Murzov
Modified: 2012-11-05 23:36 UTC (History)
2 users (show)

See Also:
Kernel Version: 3.7.0-rc1
Subsystem:
Regression: No
Bisected commit-id:

Attachments
dmesg (63.60 KB, text/plain)
2012-10-17 00:34 UTC, Igor Murzov 		Details
lspci -vvv (30.42 KB, text/plain)
2012-10-17 00:35 UTC, Igor Murzov 		Details
give each radeon_bl a unique name (2.61 KB, patch)
2012-10-17 21:24 UTC, Alex Deucher 		Details | Diff
Add an attachment (proposed patch, testcase, etc.)

Description Igor Murzov 2012-10-17 00:34:27 UTC 
Created attachment 83691 [details]
dmesg

There is an error in my dmesg:

sysfs: cannot create duplicate filename '/class/backlight/radeon_bl'

and there is no '/sys/class/backlight/radeon_bl' after system boot.
Comment 1 Igor Murzov 2012-10-17 00:35:56 UTC 
Created attachment 83701 [details]
lspci -vvv
Comment 2 Alex Deucher 2012-10-17 14:01:08 UTC 
You have a hybrid laptop with with a mux to switch between the two GPUs.  I suppose ideally we'd only create one bl device and switch control of it when the mux is switched.  I'm not sure of the best way to do that off hand at the moment.
Comment 3 Igor Murzov 2012-10-17 16:44:02 UTC 
Can I help somehow with this and other issue with hybrid systems with a mux? Looks like not much people have such configuration and linux becomes more and more buggy with regard to gpus on my laptop. I can help testing patches or may be bisect some regression for you or even inspect some code :]
Comment 4 Alex Deucher 2012-10-17 20:05:42 UTC 
The acpi backlight control should still work.
Comment 5 Alex Deucher 2012-10-17 21:24:04 UTC 
Created attachment 83751 [details]
give each radeon_bl a unique name

This patch should fix the issue, however, you'll have to use the appropriate bl device depending on which gpu is active.
Comment 6 Igor Murzov 2012-10-19 15:16:21 UTC 
The patch fixed the issue. I have two bl devices now:
# tree /sys/class/backlight/
/sys/class/backlight/
├── radeon_bl0 -> ../../devices/pci0000:00/0000:00:01.0/0000:01:05.0/drm/card0/card0-LVDS-1/radeon_bl0
└── radeon_bl1 -> ../../devices/pci0000:00/0000:00:02.0/0000:02:00.0/drm/card1/card1-LVDS-2/radeon_bl1
Comment 7 Florian Mickler 2012-11-05 23:15:22 UTC 
A patch referencing this bug report has been merged in Linux v3.7-rc3:

commit 614499b4d844dcceae5ae2f1e53a2963789a8933
Author: Alex Deucher <alexander.deucher@amd.com>
Date:   Wed Oct 17 17:20:24 2012 -0400

    drm/radeon: give each backlight a unique id
Comment 8 Igor Murzov 2012-11-05 23:36:42 UTC 
Fixed.
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