On 12/10/08 08:18, Andrew Gallatin wrote:
Paul Durrant wrote:
Andrew Gallatin wrote:
The above suggests that all my allocation requests should fail,
since all my allocation requests are for 1520 bytes, and that's
not a multiple of 4095...
Drew,
I didn't notice the 'multiple' rule when I started using it; to be
honest I just went off what I found in the source code ;-) (The relevant
bits of code are in the rootnex driver, if I remember correctly).
Let's hope nobody "fixes" the code to match the man page :)
Be very very careful here. The different platforms have different
implementations of the rootnex stuff, as I recently discovered on 32-bit
platforms. (Apparently I discovered a strange failure mode when align
== 2, but minxfer == 4. It worked on amd64, but caused an allocation
failure on 32-bit systems. Bumping align up to 4 fixed the problem in
my driver, although to be fair the problem was *probably* a bug in the
DDI DMA code for the i386.)
I would avoid depending too much on specific allocation behaviors like
this, if I had a choice. Better, I think to just allocate one or more
pages and manage the the division yourself internally.
-- Garrett
Drew
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