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SubjectRe: Address spaces on a i386 - Getting Confused
   From: Paul Sargent <Paul.Sargent@3dlabs.com>
Date: Tue, 30 Mar 1999 13:12:25 +0100

So presumably the other option is to allocate kernel memory and
then pass a pointer to it back to user space. Is that possible?

The user can't get at it, because it is in kernel space which is
protected from user accesses. If we allowed that, any user could just
set his uid to zero and become root :-)

I think unless you are willing to go into the hair the bttv driver
does, you're going to need to have the device put it into a kernel
buffer and then copy it into user space.

Since you're so adament about DMA'ing directly into user space, you've
piqued my interest, what does this card do and what is the
application? Video capture or 3d texture mapping?

Later,
David S. Miller
davem@redhat.com

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