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

Alan Cox (
Mon, 19 Jul 1999 14:18:16 +0100 (BST)

> > 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.

> 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.


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