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Diffstat (limited to 'Documentation/DMA-API.txt')
| -rw-r--r-- | Documentation/DMA-API.txt | 122 |
1 files changed, 36 insertions, 86 deletions
diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt index 5aceb88b3f8..05e2ae23686 100644 --- a/Documentation/DMA-API.txt +++ b/Documentation/DMA-API.txt @@ -4,20 +4,18 @@ James E.J. Bottomley <James.Bottomley@HansenPartnership.com> This document describes the DMA API. For a more gentle introduction -phrased in terms of the pci_ equivalents (and actual examples) see -Documentation/PCI/PCI-DMA-mapping.txt. +of the API (and actual examples) see +Documentation/DMA-API-HOWTO.txt. -This API is split into two pieces. Part I describes the API and the -corresponding pci_ API. Part II describes the extensions to the API -for supporting non-consistent memory machines. Unless you know that -your driver absolutely has to support non-consistent platforms (this -is usually only legacy platforms) you should only use the API -described in part I. +This API is split into two pieces. Part I describes the API. Part II +describes the extensions to the API for supporting non-consistent +memory machines. Unless you know that your driver absolutely has to +support non-consistent platforms (this is usually only legacy +platforms) you should only use the API described in part I. -Part I - pci_ and dma_ Equivalent API +Part I - dma_ API ------------------------------------- -To get the pci_ API, you must #include <linux/pci.h> To get the dma_ API, you must #include <linux/dma-mapping.h> @@ -27,9 +25,6 @@ Part Ia - Using large dma-coherent buffers void * dma_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_handle, gfp_t flag) -void * -pci_alloc_consistent(struct pci_dev *dev, size_t size, - dma_addr_t *dma_handle) Consistent memory is memory for which a write by either the device or the processor can immediately be read by the processor or device @@ -53,15 +48,11 @@ The simplest way to do that is to use the dma_pool calls (see below). The flag parameter (dma_alloc_coherent only) allows the caller to specify the GFP_ flags (see kmalloc) for the allocation (the implementation may choose to ignore flags that affect the location of -the returned memory, like GFP_DMA). For pci_alloc_consistent, you -must assume GFP_ATOMIC behaviour. +the returned memory, like GFP_DMA). void dma_free_coherent(struct device *dev, size_t size, void *cpu_addr, dma_addr_t dma_handle) -void -pci_free_consistent(struct pci_dev *dev, size_t size, void *cpu_addr, - dma_addr_t dma_handle) Free the region of consistent memory you previously allocated. dev, size and dma_handle must all be the same as those passed into the @@ -89,10 +80,6 @@ for alignment, like queue heads needing to be aligned on N-byte boundaries. dma_pool_create(const char *name, struct device *dev, size_t size, size_t align, size_t alloc); - struct pci_pool * - pci_pool_create(const char *name, struct pci_device *dev, - size_t size, size_t align, size_t alloc); - The pool create() routines initialize a pool of dma-coherent buffers for use with a given device. It must be called in a context which can sleep. @@ -108,9 +95,6 @@ from this pool must not cross 4KByte boundaries. void *dma_pool_alloc(struct dma_pool *pool, gfp_t gfp_flags, dma_addr_t *dma_handle); - void *pci_pool_alloc(struct pci_pool *pool, gfp_t gfp_flags, - dma_addr_t *dma_handle); - This allocates memory from the pool; the returned memory will meet the size and alignment requirements specified at creation time. Pass GFP_ATOMIC to prevent blocking, or if it's permitted (not in_interrupt, not holding SMP locks), @@ -122,9 +106,6 @@ pool's device. void dma_pool_free(struct dma_pool *pool, void *vaddr, dma_addr_t addr); - void pci_pool_free(struct pci_pool *pool, void *vaddr, - dma_addr_t addr); - This puts memory back into the pool. The pool is what was passed to the pool allocation routine; the cpu (vaddr) and dma addresses are what were returned when that routine allocated the memory being freed. @@ -132,8 +113,6 @@ were returned when that routine allocated the memory being freed. void dma_pool_destroy(struct dma_pool *pool); - void pci_pool_destroy(struct pci_pool *pool); - The pool destroy() routines free the resources of the pool. They must be called in a context which can sleep. Make sure you've freed all allocated memory back to the pool before you destroy it. @@ -144,8 +123,6 @@ Part Ic - DMA addressing limitations int dma_supported(struct device *dev, u64 mask) -int -pci_dma_supported(struct pci_dev *hwdev, u64 mask) Checks to see if the device can support DMA to the memory described by mask. @@ -159,8 +136,14 @@ driver writers. int dma_set_mask(struct device *dev, u64 mask) + +Checks to see if the mask is possible and updates the device +parameters if it is. + +Returns: 0 if successful and a negative error if not. + int -pci_set_dma_mask(struct pci_device *dev, u64 mask) +dma_set_coherent_mask(struct device *dev, u64 mask) Checks to see if the mask is possible and updates the device parameters if it is. @@ -187,9 +170,6 @@ Part Id - Streaming DMA mappings dma_addr_t dma_map_single(struct device *dev, void *cpu_addr, size_t size, enum dma_data_direction direction) -dma_addr_t -pci_map_single(struct pci_dev *hwdev, void *cpu_addr, size_t size, - int direction) Maps a piece of processor virtual memory so it can be accessed by the device and returns the physical handle of the memory. @@ -198,14 +178,10 @@ The direction for both api's may be converted freely by casting. However the dma_ API uses a strongly typed enumerator for its direction: -DMA_NONE = PCI_DMA_NONE no direction (used for - debugging) -DMA_TO_DEVICE = PCI_DMA_TODEVICE data is going from the - memory to the device -DMA_FROM_DEVICE = PCI_DMA_FROMDEVICE data is coming from - the device to the - memory -DMA_BIDIRECTIONAL = PCI_DMA_BIDIRECTIONAL direction isn't known +DMA_NONE no direction (used for debugging) +DMA_TO_DEVICE data is going from the memory to the device +DMA_FROM_DEVICE data is coming from the device to the memory +DMA_BIDIRECTIONAL direction isn't known Notes: Not all memory regions in a machine can be mapped by this API. Further, regions that appear to be physically contiguous in @@ -268,9 +244,6 @@ cache lines are updated with data that the device may have changed). void dma_unmap_single(struct device *dev, dma_addr_t dma_addr, size_t size, enum dma_data_direction direction) -void -pci_unmap_single(struct pci_dev *hwdev, dma_addr_t dma_addr, - size_t size, int direction) Unmaps the region previously mapped. All the parameters passed in must be identical to those passed in (and returned) by the mapping @@ -280,15 +253,9 @@ dma_addr_t dma_map_page(struct device *dev, struct page *page, unsigned long offset, size_t size, enum dma_data_direction direction) -dma_addr_t -pci_map_page(struct pci_dev *hwdev, struct page *page, - unsigned long offset, size_t size, int direction) void dma_unmap_page(struct device *dev, dma_addr_t dma_address, size_t size, enum dma_data_direction direction) -void -pci_unmap_page(struct pci_dev *hwdev, dma_addr_t dma_address, - size_t size, int direction) API for mapping and unmapping for pages. All the notes and warnings for the other mapping APIs apply here. Also, although the <offset> @@ -299,9 +266,6 @@ cache width is. int dma_mapping_error(struct device *dev, dma_addr_t dma_addr) -int -pci_dma_mapping_error(struct pci_dev *hwdev, dma_addr_t dma_addr) - In some circumstances dma_map_single and dma_map_page will fail to create a mapping. A driver can check for these errors by testing the returned dma address with dma_mapping_error(). A non-zero return value means the mapping @@ -311,9 +275,6 @@ reduce current DMA mapping usage or delay and try again later). int dma_map_sg(struct device *dev, struct scatterlist *sg, int nents, enum dma_data_direction direction) - int - pci_map_sg(struct pci_dev *hwdev, struct scatterlist *sg, - int nents, int direction) Returns: the number of physical segments mapped (this may be shorter than <nents> passed in if some elements of the scatter/gather list are @@ -353,9 +314,6 @@ accessed sg->address and sg->length as shown above. void dma_unmap_sg(struct device *dev, struct scatterlist *sg, int nhwentries, enum dma_data_direction direction) - void - pci_unmap_sg(struct pci_dev *hwdev, struct scatterlist *sg, - int nents, int direction) Unmap the previously mapped scatter/gather list. All the parameters must be the same as those and passed in to the scatter/gather mapping @@ -365,21 +323,23 @@ Note: <nents> must be the number you passed in, *not* the number of physical entries returned. void -dma_sync_single(struct device *dev, dma_addr_t dma_handle, size_t size, - enum dma_data_direction direction) +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(struct pci_dev *hwdev, dma_addr_t dma_handle, - size_t size, int direction) +dma_sync_single_for_device(struct device *dev, dma_addr_t dma_handle, size_t size, + enum dma_data_direction direction) void -dma_sync_sg(struct device *dev, struct scatterlist *sg, int nelems, - enum dma_data_direction direction) +dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg, int nelems, + enum dma_data_direction direction) void -pci_dma_sync_sg(struct pci_dev *hwdev, struct scatterlist *sg, - int nelems, int direction) +dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg, int nelems, + enum dma_data_direction direction) -Synchronise a single contiguous or scatter/gather mapping. All the -parameters must be the same as those passed into the single mapping -API. +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: @@ -461,9 +421,9 @@ void whizco_dma_map_sg_attrs(struct device *dev, dma_addr_t dma_addr, Part II - Advanced dma_ usage ----------------------------- -Warning: These pieces of the DMA API have no PCI equivalent. They -should also not be used in the majority of cases, since they cater for -unlikely corner cases that don't belong in usual drivers. +Warning: These pieces of the DMA API should not be used in the +majority of cases, since they cater for unlikely corner cases that +don't belong in usual drivers. If you don't understand how cache line coherency works between a processor and an I/O device, you should not be using this part of the @@ -514,16 +474,6 @@ into the width returned by this call. It will also always be a power of two for easy alignment. void -dma_sync_single_range(struct device *dev, dma_addr_t dma_handle, - unsigned long offset, size_t size, - enum dma_data_direction direction) - -Does a partial sync, starting at offset and continuing for size. You -must be careful to observe the cache alignment and width when doing -anything like this. You must also be extra careful about accessing -memory you intend to sync partially. - -void dma_cache_sync(struct device *dev, void *vaddr, size_t size, enum dma_data_direction direction) |