Messages in this thread | | | From | Oliver Neukum <> | Subject | Re: PCI DMA to small buffers on cache-incoherent arch | Date | Tue, 11 Jun 2002 16:23:30 +0200 |
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Am Dienstag, 11. Juni 2002 14:04 schrieb David S. Miller: > From: Oliver Neukum <oliver@neukum.name> > Date: Tue, 11 Jun 2002 14:06:14 +0200 > > A sparc64 is unlikely to be short on memory, or is it ? > What's wrong with always aligning on 128 bytes on sparc64 ? > A runtime check would be expensive. > > Maybe on arch FOO, target X needs no alignment when using PCI > controller Y, but for PCI controller Z it does need alignment.
Still does that justify the overhead and the complications ? Couldn't we provide for the worst case in a generic kernel and make it a compile time option ?
If I understand you correctly, we even couldn't use kmalloc() for allocating the buffers. IMHO you cannot expose that to driver writers and hope to get a useful result. So what are the alternatives ? We could either use a bounce buffer or disable caching for the page in question, which has its own set of problems.
Regards Oliver
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