On Fri, 20 Jul 2001, Andrey Petrov wrote:

: it's getting out of topic, I'm glad that there is movement towards
: improving XFree, I also think it's stupid to scan pci from the user
: space, and Xserver just should know where its device is.

: > : My opinion is that accessing memory is sometimes desired and needed
: >
: > But in the X case, it simply isn't needed, it's just used by XFree (at this
: > time) as a laziness convenience.
:
: X doesn't need access to framebuffer memory, is that what you're saying?

Your original statement, "...accessing memory is...", was in the context of
mmaping arbitrary bus addresses for scanning PCI space and doing DMA
operations.

Allowing X to mmap the video data (framebuffer) area is perfectly fine, so
long as the kernel can determine its exact location and size.  It's control
registers, and particularly those used to do DMA, that are particularly
insecure and need arbitration/validation by the kernel.

-- 
-- Todd Vierling <tv@wasabisystems.com>  *  Wasabi NetBSD:  Run with it.
-- NetBSD 1.5 now available on CD-ROM  --  http://www.wasabisystems.com/