[Bug 568611] Re: Screen brightness control fails on Dell Studio 1558

[Kamal Mostafa]

@Tito and other folks with /sys/class/backlight/acpi_video0:

To disable the "acpi_video0" backlight, boot with this kernel
parameter[1]:

    acpi_backlight=vendor

However note that when I do so on my Lenovo Thinkpad, acpi_video0
disappears but then /sys/class/backlight/thinkpad_backlight appears in
its place, so...

To disable "thinkpad_backlight", boot with this kernel parameter also:

    thinkpad_acpi.brightness_enable=0

Tito, please try booting with both of those parameters (together) and
report your results.

[1] To add kernel boot parameters, append them to the "linux" or "kernel" boot line as demonstrated here:
https://help.ubuntu.com/community/Grub2#Editing%20Menus%20During%20Boot
https://help.ubuntu.com/community/BootOptions#Change%20Boot%20Options%20Temporarily%20For%20An%20Existing%20Installation

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Screen brightness control fails on Dell Studio 1558
https://bugs.launchpad.net/bugs/568611
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