On Fri, 2005-10-07 at 17:41 -0400, Timothy Miller wrote: > The second source of commands is the indirect buffer. Indirect > buffers are linear stretches of commands. They can be privileged or > not, as specified by a flag in the ring buffer packet that initiated > the indirect transaction.
I take it that an unprivileged indirect buffer cannot upload/download things since that would allow it to read arbitrary memory. I thought that maybe it would be advantageous to allow an unprivileged indirect buffer memory uploads as well, from within the buffer area. For this, you'd need a second permission bit of course (if this kind of access is allowed) and a kind of jump command that would allow jumping within an indirect buffer. Then, the (kernel) driver could allow some process to use some kind of larger buffer it owns for commands including uploads, and that stretch of commands could use a jump to skip over a data area. The card would have to validate all memory uploads that originate from within this area to only use addresses within this, of course. I'm not sure if this is worthwhile from a programming perspective at all, or doable in the hardware; it was just some random idea... johannes
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