Subject: Re: [PATCH 2/2] ACPI Check for backlight support via ACPI video.ko otherwise use vendor ACPI drivers

From: Thomas Renninger <[email-masked]>
Date: Thu, 10 Jul 2008 13:36:04 +0200

On Thursday 10 July 2008 13:19:00 Matthew Garrett wrote:
> On Thu, Jul 10, 2008 at 01:15:18PM +0200, Thomas Renninger wrote:
> > On Thursday 10 July 2008 13:09:41 Matthew Garrett wrote:
> > > No I didn't. Please don't do this - we have all the code needed to do
> > > it properly, so there's no need to use the thinkpad_acpi driver for
> > > backlight control on this hardware.
> >
> > Ok.
> > But haven't you said there are ThinkPad BIOSes missing a specific ACPI
> > part and therefore you had the delay?
> > If you could give me a dmidecode output, I like to add it.
> > It would be great to have an example in the blacklist, then things are
> > much easier for others...
>
> No, I said that on Thinkpads with a PWM method, the PWM method has to be
> called in order to avoid the delay. There's no need for a blacklist.

Ok.
I just got a report that Dells must not use the video driver:
https://bugzilla.novell.com/show_bug.cgi?id=404627

They have a really ugly dcdbas driver which issues SMIs triggered from 
userspace.
Hmm, to do it correctly, I have to match against the alias of the dcdbas 
driver:
MODULE_ALIAS("dmi:*:[bs]vnD[Ee][Ll][Ll]*:*");
but matching for Dell should be enough.

Also not nice is that the video driver probably should not be loaded at all in 
this case.
Hmm, maybe I should check for !video_backlight_support 
&& !video_display_output_support and then do not load the video driver at 
all, it shouldn't have any functionality then, not sure...

   Thomas