Re: Check for ACPI backlight support otherwise use vendor ACPI

Zhang Rui
2008-07-31T05:25:05Z

On Thu, 2008-07-31 at 10:51 +0800, Jonathan Woithe wrote:
> > > I'm trying to sort out the status of this myself. Is the
> expectation
> > > that your patches *with* the IGD work from Matthew/Hong should
> mean that
> > > Fujitsus implementing IGD should not need fujitsu-laptop in order
> to
> > > provide working software backlight brightness control?
> > I think so.
>
> Ok.
>
> > > Or shouldn't Matthew/Hong's patchset be necessary with your patch
> in
> > > theory?
> > Thomas' patch assigns the responsibility to acpi video driver or
> > platform drivers when a laptop supports brightness/display switch
> both
> > via ACPI video extension and vendor specific control methods.
> >
> > brightness/display switch via ACPI video driver sometimes doesn't
> work
> > even if the ACPI control methods are available, and Matthew/Hong's
> patch
> > fixes this problem, on platforms with intel integrated graphics
> cards.
>
> I see.
>
> > And now, we should root cause why acpi_video_backlight_support()
> failed
> > on this laptop.
>
> Agreed.
>
> > > so allowing fujitsu-laptop to co-exist with video.ko handling the
> > > backlight (as your patches allow) is the right thing to do.
> >
> > sure, they will co-exist, but I don't think fujitsu-laptop should
> handle
> > the backlight stuff, unless it's explicitly stated via the boot
> > parameter "ï»¿acpi_backlight=vendor".
>
> For laptops with both ACPI video extensions and vendor specific
> control
> methods I agree with this. However, users of laptops which have only
> vendor
> specific control methods (of which the S7020 is one AFAIK) should not
> have
> to give any boot parameters for things to work for them.

sure.
In this case, ﻿acpi_video_backlight_support() returns false,
and vendor driver will handle the backlight switching.

> In other words,
> "acpi_backlight=vendor" should only come into play when the machine
> has the
> ACPI video extensions. I am assuming that this is the intention since
> that's what the current patches appear to do.
Yes.
>
> Is there a canonical source for Matthew/Hong's patch? To totally wrap
> this
> up I would like to try the S7020 with Matthew/Hong+Thomas.

> I doubt
> Matthew/Hong's work is relevant to the S7020 given that it's 3+ years
> old
> now, but it's best to test these things early.

Agree.
I think Matthew/Hong's patch should have no effect on your laptops, and
fujistu-laptop should handle the backlight switch as before.

thanks,
rui

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