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266 lines
8.1 KiB
266 lines
8.1 KiB
/* SPDX-License-Identifier: GPL-2.0-only */ |
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/* |
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* Pointer to dma-buf-mapped memory, plus helpers. |
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*/ |
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#ifndef __DMA_BUF_MAP_H__ |
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#define __DMA_BUF_MAP_H__ |
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#include <linux/io.h> |
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#include <linux/string.h> |
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/** |
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* DOC: overview |
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* |
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* Calling dma-buf's vmap operation returns a pointer to the buffer's memory. |
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* Depending on the location of the buffer, users may have to access it with |
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* I/O operations or memory load/store operations. For example, copying to |
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* system memory could be done with memcpy(), copying to I/O memory would be |
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* done with memcpy_toio(). |
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* |
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* .. code-block:: c |
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* |
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* void *vaddr = ...; // pointer to system memory |
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* memcpy(vaddr, src, len); |
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* |
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* void *vaddr_iomem = ...; // pointer to I/O memory |
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* memcpy_toio(vaddr, _iomem, src, len); |
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* |
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* When using dma-buf's vmap operation, the returned pointer is encoded as |
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* :c:type:`struct dma_buf_map <dma_buf_map>`. |
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* :c:type:`struct dma_buf_map <dma_buf_map>` stores the buffer's address in |
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* system or I/O memory and a flag that signals the required method of |
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* accessing the buffer. Use the returned instance and the helper functions |
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* to access the buffer's memory in the correct way. |
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* |
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* The type :c:type:`struct dma_buf_map <dma_buf_map>` and its helpers are |
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* actually independent from the dma-buf infrastructure. When sharing buffers |
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* among devices, drivers have to know the location of the memory to access |
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* the buffers in a safe way. :c:type:`struct dma_buf_map <dma_buf_map>` |
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* solves this problem for dma-buf and its users. If other drivers or |
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* sub-systems require similar functionality, the type could be generalized |
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* and moved to a more prominent header file. |
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* |
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* Open-coding access to :c:type:`struct dma_buf_map <dma_buf_map>` is |
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* considered bad style. Rather then accessing its fields directly, use one |
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* of the provided helper functions, or implement your own. For example, |
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* instances of :c:type:`struct dma_buf_map <dma_buf_map>` can be initialized |
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* statically with DMA_BUF_MAP_INIT_VADDR(), or at runtime with |
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* dma_buf_map_set_vaddr(). These helpers will set an address in system memory. |
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* |
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* .. code-block:: c |
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* |
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* struct dma_buf_map map = DMA_BUF_MAP_INIT_VADDR(0xdeadbeaf); |
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* |
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* dma_buf_map_set_vaddr(&map. 0xdeadbeaf); |
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* |
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* To set an address in I/O memory, use dma_buf_map_set_vaddr_iomem(). |
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* |
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* .. code-block:: c |
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* |
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* dma_buf_map_set_vaddr_iomem(&map. 0xdeadbeaf); |
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* |
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* Instances of struct dma_buf_map do not have to be cleaned up, but |
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* can be cleared to NULL with dma_buf_map_clear(). Cleared mappings |
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* always refer to system memory. |
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* |
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* .. code-block:: c |
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* |
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* dma_buf_map_clear(&map); |
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* |
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* Test if a mapping is valid with either dma_buf_map_is_set() or |
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* dma_buf_map_is_null(). |
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* |
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* .. code-block:: c |
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* |
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* if (dma_buf_map_is_set(&map) != dma_buf_map_is_null(&map)) |
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* // always true |
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* |
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* Instances of :c:type:`struct dma_buf_map <dma_buf_map>` can be compared |
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* for equality with dma_buf_map_is_equal(). Mappings the point to different |
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* memory spaces, system or I/O, are never equal. That's even true if both |
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* spaces are located in the same address space, both mappings contain the |
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* same address value, or both mappings refer to NULL. |
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* |
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* .. code-block:: c |
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* |
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* struct dma_buf_map sys_map; // refers to system memory |
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* struct dma_buf_map io_map; // refers to I/O memory |
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* |
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* if (dma_buf_map_is_equal(&sys_map, &io_map)) |
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* // always false |
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* |
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* A set up instance of struct dma_buf_map can be used to access or manipulate |
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* the buffer memory. Depending on the location of the memory, the provided |
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* helpers will pick the correct operations. Data can be copied into the memory |
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* with dma_buf_map_memcpy_to(). The address can be manipulated with |
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* dma_buf_map_incr(). |
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* |
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* .. code-block:: c |
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* |
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* const void *src = ...; // source buffer |
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* size_t len = ...; // length of src |
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* |
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* dma_buf_map_memcpy_to(&map, src, len); |
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* dma_buf_map_incr(&map, len); // go to first byte after the memcpy |
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*/ |
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/** |
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* struct dma_buf_map - Pointer to vmap'ed dma-buf memory. |
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* @vaddr_iomem: The buffer's address if in I/O memory |
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* @vaddr: The buffer's address if in system memory |
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* @is_iomem: True if the dma-buf memory is located in I/O |
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* memory, or false otherwise. |
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*/ |
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struct dma_buf_map { |
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union { |
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void __iomem *vaddr_iomem; |
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void *vaddr; |
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}; |
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bool is_iomem; |
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}; |
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/** |
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* DMA_BUF_MAP_INIT_VADDR - Initializes struct dma_buf_map to an address in system memory |
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* @vaddr_: A system-memory address |
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*/ |
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#define DMA_BUF_MAP_INIT_VADDR(vaddr_) \ |
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{ \ |
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.vaddr = (vaddr_), \ |
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.is_iomem = false, \ |
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} |
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/** |
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* dma_buf_map_set_vaddr - Sets a dma-buf mapping structure to an address in system memory |
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* @map: The dma-buf mapping structure |
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* @vaddr: A system-memory address |
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* |
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* Sets the address and clears the I/O-memory flag. |
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*/ |
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static inline void dma_buf_map_set_vaddr(struct dma_buf_map *map, void *vaddr) |
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{ |
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map->vaddr = vaddr; |
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map->is_iomem = false; |
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} |
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/** |
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* dma_buf_map_set_vaddr_iomem - Sets a dma-buf mapping structure to an address in I/O memory |
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* @map: The dma-buf mapping structure |
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* @vaddr_iomem: An I/O-memory address |
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* |
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* Sets the address and the I/O-memory flag. |
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*/ |
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static inline void dma_buf_map_set_vaddr_iomem(struct dma_buf_map *map, |
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void __iomem *vaddr_iomem) |
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{ |
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map->vaddr_iomem = vaddr_iomem; |
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map->is_iomem = true; |
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} |
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/** |
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* dma_buf_map_is_equal - Compares two dma-buf mapping structures for equality |
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* @lhs: The dma-buf mapping structure |
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* @rhs: A dma-buf mapping structure to compare with |
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* |
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* Two dma-buf mapping structures are equal if they both refer to the same type of memory |
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* and to the same address within that memory. |
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* |
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* Returns: |
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* True is both structures are equal, or false otherwise. |
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*/ |
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static inline bool dma_buf_map_is_equal(const struct dma_buf_map *lhs, |
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const struct dma_buf_map *rhs) |
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{ |
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if (lhs->is_iomem != rhs->is_iomem) |
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return false; |
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else if (lhs->is_iomem) |
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return lhs->vaddr_iomem == rhs->vaddr_iomem; |
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else |
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return lhs->vaddr == rhs->vaddr; |
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} |
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/** |
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* dma_buf_map_is_null - Tests for a dma-buf mapping to be NULL |
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* @map: The dma-buf mapping structure |
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* |
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* Depending on the state of struct dma_buf_map.is_iomem, tests if the |
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* mapping is NULL. |
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* |
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* Returns: |
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* True if the mapping is NULL, or false otherwise. |
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*/ |
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static inline bool dma_buf_map_is_null(const struct dma_buf_map *map) |
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{ |
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if (map->is_iomem) |
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return !map->vaddr_iomem; |
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return !map->vaddr; |
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} |
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/** |
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* dma_buf_map_is_set - Tests is the dma-buf mapping has been set |
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* @map: The dma-buf mapping structure |
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* |
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* Depending on the state of struct dma_buf_map.is_iomem, tests if the |
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* mapping has been set. |
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* |
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* Returns: |
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* True if the mapping is been set, or false otherwise. |
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*/ |
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static inline bool dma_buf_map_is_set(const struct dma_buf_map *map) |
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{ |
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return !dma_buf_map_is_null(map); |
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} |
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/** |
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* dma_buf_map_clear - Clears a dma-buf mapping structure |
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* @map: The dma-buf mapping structure |
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* |
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* Clears all fields to zero; including struct dma_buf_map.is_iomem. So |
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* mapping structures that were set to point to I/O memory are reset for |
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* system memory. Pointers are cleared to NULL. This is the default. |
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*/ |
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static inline void dma_buf_map_clear(struct dma_buf_map *map) |
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{ |
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if (map->is_iomem) { |
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map->vaddr_iomem = NULL; |
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map->is_iomem = false; |
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} else { |
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map->vaddr = NULL; |
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} |
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} |
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/** |
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* dma_buf_map_memcpy_to - Memcpy into dma-buf mapping |
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* @dst: The dma-buf mapping structure |
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* @src: The source buffer |
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* @len: The number of byte in src |
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* |
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* Copies data into a dma-buf mapping. The source buffer is in system |
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* memory. Depending on the buffer's location, the helper picks the correct |
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* method of accessing the memory. |
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*/ |
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static inline void dma_buf_map_memcpy_to(struct dma_buf_map *dst, const void *src, size_t len) |
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{ |
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if (dst->is_iomem) |
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memcpy_toio(dst->vaddr_iomem, src, len); |
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else |
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memcpy(dst->vaddr, src, len); |
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} |
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/** |
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* dma_buf_map_incr - Increments the address stored in a dma-buf mapping |
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* @map: The dma-buf mapping structure |
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* @incr: The number of bytes to increment |
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* |
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* Increments the address stored in a dma-buf mapping. Depending on the |
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* buffer's location, the correct value will be updated. |
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*/ |
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static inline void dma_buf_map_incr(struct dma_buf_map *map, size_t incr) |
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{ |
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if (map->is_iomem) |
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map->vaddr_iomem += incr; |
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else |
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map->vaddr += incr; |
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} |
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#endif /* __DMA_BUF_MAP_H__ */
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