LCD brightness capability question

[Richard Hughes]

On Tue, 2006-04-18 at 12:58 +0200, Danny Kukawka wrote:
> On Tuesday 18 April 2006 11:47, Richard Hughes wrote:
> > On Tue, 2006-04-18 at 11:15 +0200, Jan Jockusch wrote:
> > > Hello Richard,
> > >
> > > >Can you try the attached patch please. It was created using HEAD, but
> > > >should apply to 0.5.7 cleanly.
> > >
> > > It does. Even overlaying it with the Debian specific patches is no
> > > problem (a few lines of offset, that's it).
> > >
> > > >If it's successful then things should just work, and the laptop_panel
> > > >capability should be seen in hal-device-manager and gnome-power-manager.
> > >
> > > This is too good to be true. Laptop brightness control works like a
> > > charm now in gnome-power-control. You're really fast! Thanks a lot! Feel
> > > free to commit the patch ;-)
> >
> > David, good to commit?
> 
> No, it's not good to commit. 
> 
> I assume he use the generic ACPI video driver (modprobe video) and not a 
> special driver e.g. from/for futjisu. 

Ahh, gotcha.

> 1.) I can't see where you check if this machine is a) a FujitsuSiemens or/and 
> b) this special machine in your patch. If this patch go in, HAL offer set 
> brightness for all machines with loaded video module and which have this path 
> in /proc/acpi. But this happens also on several (in fact many) other machines 
> - on this point we are at:

Didn't modprobe video used to populate stuff in /sys rather
than /proc/acpi? The kernel could have changed of course...

> 2.) I see no check if the device really support set brightness. You need to 
> check if there are values returned which make sense (e.g. not <not 
> supported> )

I wasn't aware of this, sorry.

> 3.) Also if the device not return <not supported>: this mean not that set 
> brightness is supported by this machine. This can also differ in several 
> cases from bios version to bios version. And on many (maybe the most) this 
> does not work.
> 
> 4.) Also if a device support set brightness via this path the number of 
> brightness levels can differ from '8'.

So how to tell what brightness levels this supports? i.e.
how to decode:

# cat /proc/acpi/video/VGA/LCD/brightness
levels:  8 4 1 2 3 4 5 6 7 8
current: 4

> You see it make no sense to commit this in the CVS.

Sure, agreed.

Richard.