Re: AGP & non-root mmap calls: "lending" priviledges to a client
Alan Cox (alan@lxorguk.ukuu.org.uk)
Sun, 18 Jul 1999 13:05:34 +0100 (BST)
> A question that has been presented to us is that of direct mmap() access to
> AGP bridge-viewed RAM. For our AGP/GART device, the client non-root
> processes that are coordinated by the X server are handed a "magic cookie"
> that can be used to "bless" a device file descriptor (allowed inside the
> kernel) ... and thus allow any mmap as needed directly from the AGP/GART
> device. In general, then, only smart and X-server coordinated processes are
> then able to do this, enhancing stability, but decreasing unneeded
> centralization.
>
> Are there any plans to allow "handing over" priviledges to clients, from one
> process to another? Should a technique of "trusted-cookies" be used to
It already exists for general handle passing for file handles. Precision Insight
have a fairly clean working kernel module (free software) in progress for doing
the direct render resource management 'right' in a similar style to SGI.
Alan
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