Messages in this thread | | | Date | Tue, 14 Jan 2003 15:51:05 +0000 | From | Russell King <> | Subject | Re: [BK-2.5] Update the generic DMA API to take GFP_ flags on |
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On Tue, Jan 14, 2003 at 07:30:23AM -0800, David S. Miller wrote: > From: James Bottomley <James.Bottomley@steeleye.com> > Date: Tue, 14 Jan 2003 10:30:15 -0500 > > A GFP_KERNEL request is safely implemented as GFP_ATOMIC as long as the caller > checks return for NULL. for dma_alloc_coherent return checking is a > requirement because the system may return NULL anyway if it is out of mappings > even with a GFP_KERNEL flag. > > Now what about the corollary, a platform that needs > to sleep to setup the cpu mapings in a race-free manner? > > It could not ever honor GFP_ATOMIC in that case.
That got solved in recent 2.5, albiet with limit of 2MB of consistent / coherent allocations at any one time. We return NULL if we run out of space, and _all_ callers must check the return code of pci_alloc_consistent and/or dma_alloc_coherent no matter what flags they pass in.
-- Russell King (rmk@arm.linux.org.uk) The developer of ARM Linux http://www.arm.linux.org.uk/personal/aboutme.html
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