Re: ACPI_VIDEO and BACKLIGHT_CLASS_DEVICE

Alan Stern
2010-11-12T21:26:16Z

On Fri, 12 Nov 2010, Matthew Garrett wrote:

> On Thu, Nov 11, 2010 at 10:00:03PM -0500, Alan Stern wrote:
>
> > But my computer doesn't have an LCD display. It's a desktop, not a
> > laptop. So why do I need BACKLIGHT_CLASS_DEVICE to be enabled?
>
> Well, in the near future ddc-ci will be hooked up and you'll have
> backlight control over VGA if your monitor supports it, so even if we
> fix this up now you'll just end up getting it back in the near future
> because we can't tell that at build-time...
>
> > Are you saying I don't need ACPI_VIDEO if the machine doesn't have an
> > integrated LCD display? That doesn't agree with the Kconfig help
> > message.
>
> But to that, yes. The only reason to use ACPI_VIDEO is to get EDID from
> firmware (which isn't relevant on desktops) or to control backlights.
> Every other theoretical feature it has is useless in the real world.

Thanks for the information. Why does the help text for ACPI_VIDEO
mention defining the POST device or setting up a video output if the
driver doesn't do these things?

Alan Stern