Kernel support for graphics cards

[Michel Dänzer]

Please attribute your quotations properly.

On Tue, 2006-02-07 at 18:44 +0100, olafBuddenhagen at gmx.net wrote:
> 
> I think there is some misunderstanding here. The idea is *not* to have
> the kernel put limits what kind of hardware access the userspace drivers
> are allowed to do, using perfect knowledge of the hardware to decide
> what is safe and what is not. The idea is rather for the kernel to do
> the graphics hardware access *itself*, the userspace driver only telling
> what operation it wants performed.
> 
> This doesn't require any more knowledge about the hardware than doing
> the same access in userspace directly. The difference is that the kernel
> driver can ensure that only known safe operations can be invoked. Thus,
> it's actually a great advantage in case of incomplete specs.

I basically agree; this is more or less what the DRM does. Note that
this kind of interface does implicitly limit what userspace can do, and
requires careful design to balance between providing functionality,
maintaining security and limiting overhead. It's not as if simply
choosing this kind of interface automagically solves all problems.


> > (which would work only for linux btw - u'd need differnet drivers for
> > bsd, etc. etc. etc.),
> 
> That's not necessarily true. In KGI, the board-specific driver modules
> are actually system independant. It's in fact *more* portable than the
> current situation, with kernel specific DRM drivers.

The hardware specific DRM code is shared between OSs as well.


-- 
Earthling Michel Dänzer      |     Debian (powerpc), X and DRI developer
Libre software enthusiast    |   http://svcs.affero.net/rm.php?r=daenzer