linux-kernel - Re: kms in defconfig

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Message-ID: <21d7e9970904281642x348d9d26s153bc6f75159c262@mail.gmail.com>
Date:	Wed, 29 Apr 2009 09:42:05 +1000
From:	Dave Airlie <airlied@...il.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: kms in defconfig

On Tue, Apr 28, 2009 at 5:32 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Tue, 2009-04-28 at 11:54 +1000, Dave Airlie wrote:
>> On Tue, Apr 28, 2009 at 1:40 AM, Peter Zijlstra <peterz@...radead.org> wrote:
>> > On Mon, 2009-04-27 at 10:39 +0200, Ingo Molnar wrote:
>> >> * Dave Airlie <airlied@...il.com> wrote:
>> >>
>> >> > Hi guys,
>> >> >
>> >> > I just noticed CONFIG_DRM_I915_KMS is enabled for x86-64.
>> >> >
>> >> > This should never be the case, as anyone who built defconfig
>> >> > kernels before, will now get KMS enabled when really they need to
>> >> > have done userspace upgrades.
>> >>
>> >> I've yet to see such a bugreport.
>> >
>> > Whenever I accidentally enable KMS I get a dead X (happens way more
>> > often that I'd like to), I blame this on the ubuntu Xorg packages, but
>> > can't be arsed to fix it myself -- hopefully the kinky koala will fix
>> > stuff, but who knows.
>>
>> Well you can't really blame anyone else for it, since you have to put
>> the code upstream
>> in the kernel before you can release drivers that use it for distros to package.
>>
>> So it would be impossible for any distro to have shipped kms drivers in a useful
>> fashion before KMS is actually in the kernel.
>
> Can't the driver detect KMS and use it when present? In that case they
> could just ship a KMS capable driver that works either way.
>

Again it can't tell the future. The kernel can't know what userspace
driver is installed
or what driver the X server is going to run on it. So new drivers can
of course deal with both cases
as the userspace driver is kms aware, but a non-kms aware userspace cannot know
about KMS without time travel.

Once distros ship the kms aware userspaces then it should all work fine.

Dave.
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