From 9705ef7ec8c67a62474291bb4b235927bdf702db Mon Sep 17 00:00:00 2001 From: FUJITA Tomonori Date: Wed, 10 Mar 2010 15:23:17 -0800 Subject: DMA-API.txt: add dma_sync_single/sg API description This adds the description of the following eight function: dma_sync_single_for_cpu pci_dma_sync_single_for_cpu dma_sync_single_for_device pci_dma_sync_single_for_device dma_sync_sg_for_cpu pci_dma_sync_sg_for_cpu dma_sync_sg_for_device pci_dma_sync_sg_for_device It was unclear that the API permits a partial sync (some network drivers already do though). I made it clear that the sync_single API can do a partial sync but the sync_sg API can't. We could do a partial sync with the sync_sg API too, however, it's difficult for driver writers to correctly use the sync_sg API for a partial sync since the scatterlists passed in to the mapping API can't be modified. It's unlikely that driver writers want to do a partial sync with the sync_sg API (because the sync_sg API are usually used for block drivers). So I think that it's better to forbid a partial sync with the sync_sg API. Signed-off-by: FUJITA Tomonori Acked-by: David Miller Acked-by: James Bottomley Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/DMA-API.txt | 42 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 42 insertions(+) (limited to 'Documentation/DMA-API.txt') diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt index bb0e75e368b..c8db3d0dba5 100644 --- a/Documentation/DMA-API.txt +++ b/Documentation/DMA-API.txt @@ -364,6 +364,48 @@ API. Note: must be the number you passed in, *not* the number of physical entries returned. +void +dma_sync_single_for_cpu(struct device *dev, dma_addr_t dma_handle, size_t size, + enum dma_data_direction direction) +void +pci_dma_sync_single_for_cpu(struct pci_dev *hwdev, dma_addr_t dma_handle, + size_t size, int direction) +void +dma_sync_single_for_device(struct device *dev, dma_addr_t dma_handle, size_t size, + enum dma_data_direction direction) +void +pci_dma_sync_single_for_device(struct pci_dev *hwdev, dma_addr_t dma_handle, + size_t size, int direction) +void +dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg, int nelems, + enum dma_data_direction direction) +void +pci_dma_sync_sg_for_cpu(struct pci_dev *hwdev, struct scatterlist *sg, + int nelems, int direction) +void +dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg, int nelems, + enum dma_data_direction direction) +void +pci_dma_sync_sg_for_device(struct pci_dev *hwdev, struct scatterlist *sg, + int nelems, int direction) + +Synchronise a single contiguous or scatter/gather mapping for the cpu +and device. With the sync_sg API, all the parameters must be the same +as those passed into the single mapping API. With the sync_single API, +you can use dma_handle and size parameters that aren't identical to +those passed into the single mapping API to do a partial sync. + +Notes: You must do this: + +- Before reading values that have been written by DMA from the device + (use the DMA_FROM_DEVICE direction) +- After writing values that will be written to the device using DMA + (use the DMA_TO_DEVICE) direction +- before *and* after handing memory to the device if the memory is + DMA_BIDIRECTIONAL + +See also dma_map_single(). + dma_addr_t dma_map_single_attrs(struct device *dev, void *cpu_addr, size_t size, enum dma_data_direction dir, -- cgit v1.2.3