Re: [pull] drm-intel-fixes

Stéphane Marchesin
2013-05-22T16:00:22Z

On Wed, May 22, 2013 at 8:51 AM, Daniel Vetter <daniel@ffwll.ch> wrote:
> On Wed, May 22, 2013 at 5:25 PM, Stéphane Marchesin
> <stephane.marchesin@gmail.com> wrote:
>> On Wed, May 22, 2013 at 12:13 AM, Daniel Vetter <daniel@ffwll.ch> wrote:
>>> On Wed, May 22, 2013 at 3:24 AM, Stéphane Marchesin
>>> <stephane.marchesin@gmail.com> wrote:
>>>> On Mon, Sep 10, 2012 at 12:28 AM, Daniel Vetter <daniel@ffwll.ch> wrote:
>>>>> Hi Dave,
>>>>>
>>>>> You're pull just reminded me that I've been sitting on a few small -fixes,
>>>>> too. Nothing really major at all:
>>>>> - fixup edp setup sequence (Dave)
>>>>> - disable sdvo hotplug for real, this is a fixup for a messed-up
>>>>> regression fixer (Jani)
>>>>> - don't expose dysfunctional backlight driver (Jani)
>>>>
>>>> Hi Daniel,
>>>>
>>>> This change ("don't expose dysfunctional backlight driver") regresses
>>>> the backlight on Chromebooks, where we don't run the vbios.
>>>
>>> Presuming the patch works as advertised it only stops publishing an
>>> intel backlight driver which won't work. How does that break stuff?
>>>
>>
>> Well it probably works as advertised to avoid exposing some broken
>> backlight, but the problem is that it also stops exposing a working
>> backlight on Chromebooks. However it sounds like the initial patch is
>> specific to a broken machine, so maybe a dmi match is more
>> appropriate?
>
> I prefer a dmi match for chromebooks since the behaviour of fixing up
> the backlight after i915.ko is loaded seems rather peculiar to your
> setup.

It has nothing to do with Chromebooks though, but more with the fact
that we don't run vbios. This isn't a property of the hardware.

>
>>> Or do you somehow update the max blc stuff only once i915.ko is loaded?
>>>
>>
>> Yup that's what used to happen.
>
> What/when exactly does that happen?

Before the regression, the code was:

if (max == 0) {
i915_set_default_max_backlight

which would make it work. And now that doesn't run and therefore it breaks.

Stéphane

> -Daniel
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch