[Bug 311716] Re: The slider brightness Applet has value inverted after the last update (2.6.27-11)

[Stefan Bader]

I would like to try to summarize the various issues as they appear to me
reading the comments. Unfortunately we now seem to have a whole
collection of similar but yet different problems in one huge bug and
maybe we could untangle it by splitting of separate bugs for those.

1. an inverted brightness control (as initially reported in the bug)
    There has been a patch in 2.6.27-13.29 that, in theory, should address this by
    "ACPI: video: Fix reversed brightness behavior on ThinkPad SL series" (lp#330200)
   So, starting with the mentioned kernel, the values in the acpi brightness control should get sorted
   from small to large numbers.
2. No brightness control with the acpi brightness controls present.
    This, as far as I know, affects only ThinkPad/Lenovo laptops and it should be indicated by a dmesg
    entry from thinkpad_acpi saying "standard ACPI backlight interface available, not loading native
    one...". For those, the workaround would be to use "options thinkpad_acpi brightness_enable=1"
    in a file in /etc/modprobe.d. Maybe we should make this the default, though that should be tested
    well, in order not to break yet some other machines.
3. No brightness control without the acpi controls present
    The one case of that I saw was an acer and indeed there is a bug in Intrepi'ds acer-wmi that
    reverts the intended behavior (back off if no acpi support is there but stay if there is).
4. Brightness control working through the acpi interface (echoing values to the sysfs controls)
    but not through the Desktop interface. Maybe because there have been changes to prevent
    multiple  acpi devices from creating the same VID entry n sysfs. So that could be a Desktop
    issue.

I would propose to open new bugs for 2-4 and verify and keep tracking 1 here. For 2, there seems to be a report open (lp#324061) and it would be best to track that issue there. For 3, lp#333386 seems the one matching best but for 4 I did not find a report that sounded like it described that issue. Maybe someone is more successful and could point others there or open a new report for it.
Finally 1: is this still an issue with the latest -proposed kernel? If yes, could you add the Laptop vendor and model as well as the output of "grep -r . /proc/acpi/video" here?

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The slider brightness Applet has value inverted after the last update (2.6.27-11)
https://bugs.launchpad.net/bugs/311716
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