[Bug 257827] Re: brightness changes twice when using hotkeys

[Steve Beattie]

@apw: per our discussion, I tried both separately blacklisting the video
module and adding the brightness_enable=1 option to the thinkpad_acpi
module.

Blacklisting the video module had no effect; adjusting brightness was
broken entirely and even worse, the brightness was set at the lowest
setting. g-p-m locked up entirely when trying to adjust the screen
brightness.

Adding the brightness_enable=1 option to the thinkpad_acpi module
options caused brightness settings to start working; g-p-m was able to
adjust the brightness settings. Also, with that option, the directory
/sys/devices/virtual/backlight/thinkpad_screen/ showed up, and writing
values to the brightness file in that directory changed the display
brightness.

Writing values to /sys/devices/virtual/backlight/acpi_video0/brightness
had no effect in any of the kernels I booted (with the video module
blacklisted, that path did not exist). When the -10.20 kernel is booted,
there's also a /sys/devices/virtual/backlight/acpi_video1/ directory;
writing values to the brightness file in that directory also adjusted
the screen's brightness.

-- 
brightness changes twice when using hotkeys
https://bugs.launchpad.net/bugs/257827
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