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2011-07-27Improve slave/cyclic DMA engine documentationRussell King - ARM Linux1-70/+164
Improve the documentation for the slave and cyclic DMA engine support reformatting it for easier reading, adding further APIs, splitting it into five steps, and including references to the documentation in dmaengine.h. Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> [Fixed the index title to reflect new changes] Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2011-05-26dmaengine: Add API documentation for slave dma usageVinod Koul1-1/+96
Signed-off-by: Vinod Koul <vinod.koul@intel.com> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
2009-01-06async_tx, dmaengine: document channel allocation and api reworkDan Williams1-0/+1
"Wouldn't it be better if the dmaengine layer made sure it didn't pass the same channel several times to a client? I mean, you seem concerned that the memcpy() API should be transparent and easy to use, but the whole registration interface is just ridiculously complicated..." - Haavard The dmaengine and async_tx registration/allocation interface is indeed needlessly complicated. This redesign has the following goals: 1/ Simplify reference counting: dma channels are not something one would expect to be hotplugged, it should be an exceptional event handled by drivers not something clients should be mandated to handle in a callback. The common case channel removal event is 'rmmod <dma driver>', which for simplicity should be disallowed if the channel is in use. 2/ Add an interface for requesting exclusive access to a channel suitable to device-to-memory users. 3/ Convert all memory-to-memory users over to a common allocator, the goal here is to not have competing channel allocation schemes. The only competition should be between device-to-memory exclusive allocations and the memory-to-memory usage case where channels are shared between multiple "clients". Cc: Haavard Skinnemoen <haavard.skinnemoen@atmel.com> Cc: Neil Brown <neilb@suse.de> Cc: Jeff Garzik <jeff@garzik.org> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Dan Williams <dan.j.williams@intel.com>