Bug#509307: xbacklight: -set does nothing if it thinks the setting is already correct

[Brice Goglin <Brice.Goglin@ens-lyon.org>]

Reuben Thomas wrote:
> Package: xbacklight
> Severity: normal
>
> xbacklight -set sometimes has no effect. For example, when I suspend and
> resume my laptop, the backlight is reset to 100%, but is still reported
> as whatever I set it to before. xbacklight seems to do nothing if I try
> to set it to the same value; instead, I must first set it to a different
> value.
>   

It may be a bug in the driver. If the driver doesn't reset its backlight
value on suspend/resume, xbacklight will read a wrong value from it, and
thus do nothing if the set the same value.

Did you actually ever observe the bug when not resuming from suspend?

Which driver do you use? Can you try the latest driver from experimental
and a recent kernel?

Brice