Messages in this thread | | | Date | Mon, 1 Jun 2009 17:08:09 +0900 | Subject | Re: [PATCH] asm-generic: add dma-mapping-linear.h | From | FUJITA Tomonori <> |
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On Mon, 1 Jun 2009 08:51:14 +0100 Russell King <rmk+lkml@arm.linux.org.uk> wrote:
> On Mon, Jun 01, 2009 at 01:02:42PM +0900, FUJITA Tomonori wrote: > > Where can I find dma_coherent_dev? > > > > I don't fancy this since this is architecture-specific stuff (not > > generic things). > > It _is_ very architecture specific. The coherent-ness of devices hardly > depends on the device itself. Eg, PCI devices on x86 are coherent, but > on ARM they aren't. > > > > +static inline void > > > +dma_unmap_single(struct device *dev, dma_addr_t dma_addr, size_t size, > > > + enum dma_data_direction direction) > > > +{ > > > + debug_dma_unmap_page(dev, dma_addr, size, direction, true); > > Future ARMs will need to do something on unmaps. > > > > +static inline void > > > +dma_sync_single_for_cpu(struct device *dev, dma_addr_t dma_handle, size_t size, > > > + enum dma_data_direction direction) > > > +{ > > > + debug_dma_sync_single_for_cpu(dev, dma_handle, size, direction); > > > +} > > > + > > > +static inline void > > > +dma_sync_single_range_for_cpu(struct device *dev, dma_addr_t dma_handle, > > > + unsigned long offset, size_t size, > > > + enum dma_data_direction direction) > > > +{ > > > + debug_dma_sync_single_range_for_cpu(dev, dma_handle, > > > + offset, size, direction); > > > +} > > > > This looks wrong. You put dma_coherent_dev hook in sync_*_for_device > > but why you don't need it sync_*_for_cpu. It's architecture > > specific. Some need both, some need either, and some need nothing. > > If you're non-coherent, you need to implement the sync APIs. > > > > +static inline int > > > +dma_mapping_error(struct device *dev, dma_addr_t dma_addr) > > > +{ > > > + return 0; > > So mappings never fail?
Hmm, possibly, you might misunderstand what he is trying to do.
http://lkml.org/lkml/2009/5/28/393:
This adds a version of the dma-mapping API to asm-generic that can be used by most architectures that only need a linear mapping.
= The original thread is here (I'm not sure if we can have something clean and useful like this header file):
http://lkml.org/lkml/2009/5/19/262
I think that ARM can't be an user of this (ARM needs more complicated dma mapping stuff).
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