Messages in this thread |  | | | Subject | Re: Proposal for new generic device API: dma_get_required_mask() | | From | James Bottomley <> | | Date | 19 Jun 2004 10:00:50 -0500 |
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On Fri, 2004-06-18 at 18:07, Krzysztof Halasa wrote: > James Bottomley <James.Bottomley@steeleye.com> writes: > I don't think so. We already have separate masks for coherent > and non-coherent mappings (in PCI API, and I'm told it's to be extended > to DMA API as well). And we need them. > > The problem is we're missing DMA masks for non-alloc calls (depending > on the platform) and thus that it isn't very reliable. Drivers which > need this are forced to bounce buffers themselves, and many of them > will not work on 64-bit platforms (as of ~ 2.6.0, I don't check that > regularly). And yes, we really need reliable masks for non-alloc > mappings.
Could you elaborate on this? In the current scheme the coherent mask is for descriptor allocation (i.e. dma_alloc_coherent()) and the dma_mask represents the bus physical addresses to which the device can DMA directly; there's not much more the DMA API really does, what do you think is missing?
James
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