Messages in this thread | | | Date | Wed, 04 Dec 2002 19:54:56 -0500 | From | Jeff Garzik <> | Subject | Re: [RFC] generic device DMA implementation |
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David Gibson wrote: > On Wed, Dec 04, 2002 at 11:47:14AM -0600, James Bottomley wrote: >>The new DMA API allows a driver to advertise its level of consistent memory >>compliance to dma_alloc_consistent. There are essentially two levels: >> >>- I only work with consistent memory, fail if I cannot get it, or >>- I can work with inconsistent memory, try consistent first but return >>inconsistent if it's not available. > > > Do you have an example of where the second option is useful? Off hand > the only places I can think of where you'd use a consistent_alloc() > rather than map_single() and friends is in cases where the hardware's > behaviour means you absolutely positively have to have consistent > memory.
agreed, good catch. Returning inconsistent memory when you asked for consistent makes not much sense: the programmer either knows what the hardware wants, or the programmer is silly and should not be using alloc_consistent anyway.
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