Messages in this thread | | | Date | Wed, 15 Sep 1999 14:24:10 -0400 | From | Jeff Garzik <> | Subject | Re: MTRR setting and framebuffer driver |
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David Wragg wrote: > > Jeff Garzik <jgarzik@pobox.com> writes: > > Jamie Lokier wrote: > > > If we can assume that unregistered physical address space is never > > > accessed (whatever the bus), it's safe to have MTRRs covering that space > > > redundantly. > > > > I don't think that assumption can be made until all the drivers use the > > new resource code. > > Some of the fb drivers get out of the way when the X server wants to > talk directly to the graphics hardware, correct? Then in general, that > assumption doesn't hold even when all drivers register their address > ranges.
There are two valid cases, no fbdev + X, or fbdev + XF86_FBDev (a special X server). The third case, fbdev + non-XF86_FBDev server, often works, but is just asking for trouble.
> But it might work if kernel drivers drop their MTRR allocations when > the X server takes over.
If the kernel driver allocated MTRRs, it should communicate that to the Xserver fbdev support module.
Under fbdev, the X server is simply one among any number of graphics applications. The kernel cannot simply drop its MTRRs when the fbdev device is opened by a user application. And writing special case code in fbdev just for X is the wrong way to go, IMHO.
Jeff
-- Custom driver development | Never worry about theory as long Open source programming | as the machinery does what it's | supposed to do. -- R. A. Heinlein
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