Re: AGP & non-root mmap calls: "lending" priviledges to a client

Thomas Roell (
Mon, 19 Jul 1999 07:27:54 -0600 (MDT)

In your message of 19 July 1999 you write:

> > > It already exists for general handle passing for file handles.
> >
> > Can you give me a pointer to that meachansim, and also how it's
> > handled in other Unix like operating systems ?
> Borrow a copy of Stevens advanced unix programming and look at file handle
> passing. Basically you can pass a file handle from one process to another
> over a socket. Its an interesting and sadly underused unix feature.
> For example a client could open a file and pass the handle to a server to
> print. In your case you could open /dev/mem and pass it to a client.

Arl. You know I have programmed with UNIX for quite a while, but never
ran across this one. Thanx for the hint.

> > boards (from the documentation I have seen). What we are trying to
> > make available is a relatively simple AGP driver that addresses the
> > limited area of AGP mapping and management without trying to cover
> > all the issues that are involved to do direct rendering.
> For simple AGP addressing/management you should check the Matrox Gx00
> 3D list. I did them a basic DMA driver (dmaram.c in 2.2.10ac*) and they
> have extended this to do virtual allocations and AGP mappings.

Hmmm ... As I said before, we have already a working, complete and
tested driver and you like to pass that over to the freeware
community. All that's missing is this little authorization thing. I
have seen your's dmaram.c driver, which is great for normal PCI DMA
style stuff (without AGP GART). What our little driver does, is simply
populating the GART, mapping CPU pages behind it, setting up essential
MTRR stuff and so on. There are a couple of neat tricks in it, that
work around a few problems in both graphics chips as well as
motherboard chips. After supporting now half a dozen graphics chip
families for HW 3D and AGP you realize that things don't always work
as the databooks say ;-)

Who is the person to send a driver like this to ?

- Thomas

	     Thomas Roell   /\	       An imperfect plan executed violently
	     Xi Graphics   /  \/\ _     is far superior to a perfect plan.	  /   /	 \ \	 
			 / Oelch! \ \		  George Patton

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