linux-kernel - Re: [RFC] enhancing the kernel's graphics subsystem

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Message-ID: <21d7e9970705220735j37bc8eeck87db7193c08c4c24@mail.gmail.com>
Date:	Tue, 22 May 2007 15:35:02 +0100
From:	"Dave Airlie" <airlied@...il.com>
To:	"Jon Smirl" <jonsmirl@...il.com>
Cc:	"Jesse Barnes" <jbarnes@...tuousgeek.org>,
	"Jeff Garzik" <jeff@...zik.org>,
	"Jesse Barnes" <jesse.barnes@...el.com>,
	linux-kernel@...r.kernel.org,
	"Antonino A. Daplas" <adaplas@...il.com>
Subject: Re: [RFC] enhancing the kernel's graphics subsystem

On 5/22/07, Jon Smirl <jonsmirl@...il.com> wrote:
> On 5/21/07, Jesse Barnes <jbarnes@...tuousgeek.org> wrote:
> > Jon, that's why I'm posting this stuff in the first place! :)  Again, if
> > you have specific problems with the proposed interfaces (problems that
> > would preclude your wishlist from being fully implementable), please let
> > me know (preferably with specifics).
>
> A simple place to start is OOPS display while in graphics mode. If we
> going to tear up the kernel graphics system this is something that
> needs to be fixed.
>
> I don't think it is safe for the OOPS code to attempt a mode change to
> text mode when the OOPS happens. The OOPS could have happened in a 3D
> driver and left the GPU messed up. The safest thing to do is to
> display the OOPS using the mode that is already set.
>
> This implies that the kernel driver needs to track the dimensions and
> location of the framebuffer and whether it is in text/graphics mode
> (this hasn't been possible before because X never tells the kernel
> what mode it is setting). You also need to bring in the bitmap copy
> code and fonts over from fbdev. When the OOPS happens you use this
> info to paint the OOPS onto the screen. The code from fbdev will let
> you display text in graphics mode entirely in kernel context. The
> driver should also attempt to stop the GPU to try and make sure it
> doesn't erase the OOPS display.

What does this have to do with Jesse's patches? this is a totally
orthogonal issue..

We will fix this once we have the basic modesetting code working,

> Another simple thing that needs to be built is a mechanism to run the
> VBIOS in x86 mode when the driver is first loaded. This can be
> achieved by using call_usermode helper to trigger an external app. You
> also need to get the x86 emulator working so that this will work on
> non-x86 platforms (benh has already done this). I've aput the hooks
> into place to give you access to the VBIOS from sysfs. This app is a
> prime candidate for klibc. This app is strongly coupled to the problem
> of VGA arbitration.
>

Again orthogonal problem, VGA arbitration isn't going to matter for
this stuff, and we can have initramfs sw do vbetool post on
non-initialised cards at startup even now (it may not always work as
some cards may not have BIOSes in the right place s and we need the
VGA arb to work to do it properly...)

These are nothing to do with the work we are doing, and I think a big
part of your problem with working on this previously is you have
linked together a group of orthogonal problems into one big problem,
when really there are 5-10 problems all of which can be solved
separately...

Dave.
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