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dma-buf-map: Add memcpy and pointer-increment interfaces

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To do framebuffer updates, one needs memcpy from system memory and a
pointer-increment function. Add both interfaces with documentation.

v5:
	* include <linux/string.h> to build on sparc64 (Sam)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Tested-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20201103093015.1063-10-tzimmermann@suse.de
This commit is contained in:
Thomas Zimmermann 2020-11-03 10:30:14 +01:00
parent a859555689
commit b4e7090c24
1 changed files with 63 additions and 10 deletions
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73
include/linux/dma-buf-map.h
View file

@ -7,6 +7,7 @@
#define __DMA_BUF_MAP_H__
#include <linux/io.h>
#include <linux/string.h>
/**
* DOC: overview
@ -32,6 +33,14 @@
* accessing the buffer. Use the returned instance and the helper functions
* to access the buffer's memory in the correct way.
*
* The type :c:type:`struct dma_buf_map <dma_buf_map>` and its helpers are
* actually independent from the dma-buf infrastructure. When sharing buffers
* among devices, drivers have to know the location of the memory to access
* the buffers in a safe way. :c:type:`struct dma_buf_map <dma_buf_map>`
* solves this problem for dma-buf and its users. If other drivers or
* sub-systems require similar functionality, the type could be generalized
* and moved to a more prominent header file.
*
* Open-coding access to :c:type:`struct dma_buf_map <dma_buf_map>` is
* considered bad style. Rather then accessing its fields directly, use one
* of the provided helper functions, or implement your own. For example,
@ -51,6 +60,14 @@
*
* dma_buf_map_set_vaddr_iomem(&map. 0xdeadbeaf);
*
* Instances of struct dma_buf_map do not have to be cleaned up, but
* can be cleared to NULL with dma_buf_map_clear(). Cleared mappings
* always refer to system memory.
*
* .. code-block:: c
*
* dma_buf_map_clear(&map);
*
* Test if a mapping is valid with either dma_buf_map_is_set() or
* dma_buf_map_is_null().
*
@ -73,17 +90,19 @@
* if (dma_buf_map_is_equal(&sys_map, &io_map))
* // always false
*
* Instances of struct dma_buf_map do not have to be cleaned up, but
* can be cleared to NULL with dma_buf_map_clear(). Cleared mappings
* always refer to system memory.
* A set up instance of struct dma_buf_map can be used to access or manipulate
* the buffer memory. Depending on the location of the memory, the provided
* helpers will pick the correct operations. Data can be copied into the memory
* with dma_buf_map_memcpy_to(). The address can be manipulated with
* dma_buf_map_incr().
*
* The type :c:type:`struct dma_buf_map <dma_buf_map>` and its helpers are
* actually independent from the dma-buf infrastructure. When sharing buffers
* among devices, drivers have to know the location of the memory to access
* the buffers in a safe way. :c:type:`struct dma_buf_map <dma_buf_map>`
* solves this problem for dma-buf and its users. If other drivers or
* sub-systems require similar functionality, the type could be generalized
* and moved to a more prominent header file.
* .. code-block:: c
*
* const void *src = ...; // source buffer
* size_t len = ...; // length of src
*
* dma_buf_map_memcpy_to(&map, src, len);
* dma_buf_map_incr(&map, len); // go to first byte after the memcpy
*/
/**
@ -210,4 +229,38 @@ static inline void dma_buf_map_clear(struct dma_buf_map *map)
}
}
/**
* dma_buf_map_memcpy_to - Memcpy into dma-buf mapping
* @dst: The dma-buf mapping structure
* @src: The source buffer
* @len: The number of byte in src
*
* Copies data into a dma-buf mapping. The source buffer is in system
* memory. Depending on the buffer's location, the helper picks the correct
* method of accessing the memory.
*/
static inline void dma_buf_map_memcpy_to(struct dma_buf_map *dst, const void *src, size_t len)
{
if (dst->is_iomem)
memcpy_toio(dst->vaddr_iomem, src, len);
else
memcpy(dst->vaddr, src, len);
}
/**
* dma_buf_map_incr - Increments the address stored in a dma-buf mapping
* @map: The dma-buf mapping structure
* @incr: The number of bytes to increment
*
* Increments the address stored in a dma-buf mapping. Depending on the
* buffer's location, the correct value will be updated.
*/
static inline void dma_buf_map_incr(struct dma_buf_map *map, size_t incr)
{
if (map->is_iomem)
map->vaddr_iomem += incr;
else
map->vaddr += incr;
}
#endif /* __DMA_BUF_MAP_H__ */