dma-mapping: provide a generic DMA_MAPPING_ERROR
Error handling of the dma_map_single and dma_map_page APIs is a little problematic at the moment, in that we use different encodings in the returned dma_addr_t to indicate an error. That means we require an additional indirect call to figure out if a dma mapping call returned an error, and a lot of boilerplate code to implement these semantics. Instead return the maximum addressable value as the error. As long as we don't allow mapping single-byte ranges with single-byte alignment this value can never be a valid return. Additionaly if drivers do not check the return value from the dma_map* routines this values means they will generally not be pointed to actual memory. Once the default value is added here we can start removing the various mapping_error methods and just rely on this generic check. Signed-off-by: NChristoph Hellwig <hch@lst.de> Reviewed-by: NRobin Murphy <robin.murphy@arm.com> Acked-by: NRussell King <rmk+kernel@armlinux.org.uk> Acked-by: NLinus Torvalds <torvalds@linux-foundation.org>
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