Re: [Bugme-new] [Bug 9995] New: 2.6.25-rc1 regression - IBM ACPI backlight controlls do not work

Re: [Bugme-new] [Bug 9995] New: 2.6.25-rc1 regression - IBM ACPI backlight controlls do not work

[Andrew Morton]

On Fri, 15 Feb 2008 04:51:15 -0800 (PST)
bugme-daemon@bugzilla.kernel.org wrote:

> http://bugzilla.kernel.org/show_bug.cgi?id=9995
> 
>            Summary: 2.6.25-rc1 regression - IBM ACPI backlight controlls do
>                     not work
>            Product: ACPI
>            Version: 2.5
>      KernelVersion: 2.6.25-rc1
>           Platform: All
>         OS/Version: Linux
>               Tree: Mainline
>             Status: NEW
>           Severity: normal
>           Priority: P1
>          Component: BIOS
>         AssignedTo: acpi_bios@kernel-bugs.osdl.org
>         ReportedBy: xhejtman@fi.muni.cz
> 
> 
> Latest working kernel version: 2.6.24
> Earliest failing kernel version: 2.6.25-rc1
> Distribution: Ubuntu/Hardy
> Hardware Environment: ThinkPad T61
> Software Environment: n/a
> Problem Description: /sys/class/backlight/acpi_video0 does not control
> backlight, nothing happens if I change brightness.
> 
> Steps to reproduce: echo {15,5,0} > /sys/class/backlight/acpi_video0/brightness 
> nothing happens.
> 

I've lost the plot on what's happening with backlight.  I think you're
about to find that this is not-a-bug, even though it stopped working.

Re: [Bugme-new] [Bug 9995] New: 2.6.25-rc1 regression - IBM ACPI backlight controlls do not work

[Lukas Hejtmanek]

On Fri, Feb 15, 2008 at 12:21:37PM -0800, Andrew Morton wrote:
> I've lost the plot on what's happening with backlight.  I think you're
> about to find that this is not-a-bug, even though it stopped working.

Why do you think that it is not-a-bug even if it stopped working? I don't
think it is a feature as acpi video driver should control backlight levels on
laptop that provides generic ACPI based backlight support which is the case of
ThinkPad T61. Or at least it used to be with up to 2.6.24 kernels.

I can read sane values from /sys/class/backlight/acpi_video0/* but changing them
has no effect on the backlight.

-- 
Lukáš Hejtmánek
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Re: [Bugme-new] [Bug 9995] New: 2.6.25-rc1 regression - IBM ACPI backlight controlls do not work

[Matthew Garrett]

No, this one is a bug. I'll try to deal with it.

-- 
Matthew Garrett | mjg59@srcf.ucam.org