Viewing file:  dma-buf-map.h (8.12 KB) -rw-r--r--
Select action/file-type:
 (+) |  (+) |  (+) | Code (+) | Session (+) |  (+) | SDB (+) |  (+) |  (+) |  (+) |  (+) |  (+) |
/* SPDX-License-Identifier: GPL-2.0-only */
/*
* Pointer to dma-buf-mapped memory, plus helpers.
*/
#ifndef __DMA_BUF_MAP_H__
#define __DMA_BUF_MAP_H__
#include <linux/io.h>
#include <linux/string.h>
/**
* DOC: overview
*
* Calling dma-buf's vmap operation returns a pointer to the buffer's memory.
* Depending on the location of the buffer, users may have to access it with
* I/O operations or memory load/store operations. For example, copying to
* system memory could be done with memcpy(), copying to I/O memory would be
* done with memcpy_toio().
*
* .. code-block:: c
*
* void *vaddr = ...; // pointer to system memory
* memcpy(vaddr, src, len);
*
* void *vaddr_iomem = ...; // pointer to I/O memory
* memcpy_toio(vaddr, _iomem, src, len);
*
* When using dma-buf's vmap operation, the returned pointer is encoded as
* :c:type:`struct dma_buf_map <dma_buf_map>`.
* :c:type:`struct dma_buf_map <dma_buf_map>` stores the buffer's address in
* system or I/O memory and a flag that signals the required method of
* 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,
* instances of :c:type:`struct dma_buf_map <dma_buf_map>` can be initialized
* statically with DMA_BUF_MAP_INIT_VADDR(), or at runtime with
* dma_buf_map_set_vaddr(). These helpers will set an address in system memory.
*
* .. code-block:: c
*
* struct dma_buf_map map = DMA_BUF_MAP_INIT_VADDR(0xdeadbeaf);
*
* dma_buf_map_set_vaddr(&map. 0xdeadbeaf);
*
* To set an address in I/O memory, use dma_buf_map_set_vaddr_iomem().
*
* .. code-block:: c
*
* 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().
*
* .. code-block:: c
*
* if (dma_buf_map_is_set(&map) != dma_buf_map_is_null(&map))
* // always true
*
* Instances of :c:type:`struct dma_buf_map <dma_buf_map>` can be compared
* for equality with dma_buf_map_is_equal(). Mappings the point to different
* memory spaces, system or I/O, are never equal. That's even true if both
* spaces are located in the same address space, both mappings contain the
* same address value, or both mappings refer to NULL.
*
* .. code-block:: c
*
* struct dma_buf_map sys_map; // refers to system memory
* struct dma_buf_map io_map; // refers to I/O memory
*
* if (dma_buf_map_is_equal(&sys_map, &io_map))
* // always false
*
* 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().
*
* .. 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
*/
/**
* struct dma_buf_map - Pointer to vmap'ed dma-buf memory.
* @vaddr_iomem: The buffer's address if in I/O memory
* @vaddr: The buffer's address if in system memory
* @is_iomem: True if the dma-buf memory is located in I/O
* memory, or false otherwise.
*/
struct dma_buf_map {
union {
void __iomem *vaddr_iomem;
void *vaddr;
};
bool is_iomem;
};
/**
* DMA_BUF_MAP_INIT_VADDR - Initializes struct dma_buf_map to an address in system memory
* @vaddr_: A system-memory address
*/
#define DMA_BUF_MAP_INIT_VADDR(vaddr_) \
{ \
.vaddr = (vaddr_), \
.is_iomem = false, \
}
/**
* dma_buf_map_set_vaddr - Sets a dma-buf mapping structure to an address in system memory
* @map: The dma-buf mapping structure
* @vaddr: A system-memory address
*
* Sets the address and clears the I/O-memory flag.
*/
static inline void dma_buf_map_set_vaddr(struct dma_buf_map *map, void *vaddr)
{
map->vaddr = vaddr;
map->is_iomem = false;
}
/**
* dma_buf_map_set_vaddr_iomem - Sets a dma-buf mapping structure to an address in I/O memory
* @map: The dma-buf mapping structure
* @vaddr_iomem: An I/O-memory address
*
* Sets the address and the I/O-memory flag.
*/
static inline void dma_buf_map_set_vaddr_iomem(struct dma_buf_map *map,
void __iomem *vaddr_iomem)
{
map->vaddr_iomem = vaddr_iomem;
map->is_iomem = true;
}
/**
* dma_buf_map_is_equal - Compares two dma-buf mapping structures for equality
* @lhs: The dma-buf mapping structure
* @rhs: A dma-buf mapping structure to compare with
*
* Two dma-buf mapping structures are equal if they both refer to the same type of memory
* and to the same address within that memory.
*
* Returns:
* True is both structures are equal, or false otherwise.
*/
static inline bool dma_buf_map_is_equal(const struct dma_buf_map *lhs,
const struct dma_buf_map *rhs)
{
if (lhs->is_iomem != rhs->is_iomem)
return false;
else if (lhs->is_iomem)
return lhs->vaddr_iomem == rhs->vaddr_iomem;
else
return lhs->vaddr == rhs->vaddr;
}
/**
* dma_buf_map_is_null - Tests for a dma-buf mapping to be NULL
* @map: The dma-buf mapping structure
*
* Depending on the state of struct dma_buf_map.is_iomem, tests if the
* mapping is NULL.
*
* Returns:
* True if the mapping is NULL, or false otherwise.
*/
static inline bool dma_buf_map_is_null(const struct dma_buf_map *map)
{
if (map->is_iomem)
return !map->vaddr_iomem;
return !map->vaddr;
}
/**
* dma_buf_map_is_set - Tests is the dma-buf mapping has been set
* @map: The dma-buf mapping structure
*
* Depending on the state of struct dma_buf_map.is_iomem, tests if the
* mapping has been set.
*
* Returns:
* True if the mapping is been set, or false otherwise.
*/
static inline bool dma_buf_map_is_set(const struct dma_buf_map *map)
{
return !dma_buf_map_is_null(map);
}
/**
* dma_buf_map_clear - Clears a dma-buf mapping structure
* @map: The dma-buf mapping structure
*
* Clears all fields to zero; including struct dma_buf_map.is_iomem. So
* mapping structures that were set to point to I/O memory are reset for
* system memory. Pointers are cleared to NULL. This is the default.
*/
static inline void dma_buf_map_clear(struct dma_buf_map *map)
{
if (map->is_iomem) {
map->vaddr_iomem = NULL;
map->is_iomem = false;
} else {
map->vaddr = NULL;
}
}
/**
* 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__ */
|