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![Daniel Vetter](/assets/img/avatar_default.png)
I wanted to look up something and noticed the hyperlink doesn't work. While fixing that also noticed a trivial kerneldoc comment typo in the same section, fix that too. Reviewed-by: Michael J. Ruhl <michael.j.ruhl@intel.com> Reviewed-by: Simon Ser <contact@emersion.fr> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20201204200242.2671481-1-daniel.vetter@ffwll.ch
266 lines
8.1 KiB
C
266 lines
8.1 KiB
C
/* 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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