参照元†
/**
* struct vb2_mem_ops - memory handling/memory allocator operations
* @alloc: allocate video memory and, optionally, allocator private data,
* return NULL on failure or a pointer to allocator private,
* per-buffer data on success; the returned private structure
* will then be passed as buf_priv argument to other ops in this
* structure. Additional gfp_flags to use when allocating the
* are also passed to this operation. These flags are from the
* gfp_flags field of vb2_queue.
* @put: inform the allocator that the buffer will no longer be used;
* usually will result in the allocator freeing the buffer (if
* no other users of this buffer are present); the buf_priv
* argument is the allocator private per-buffer structure
* previously returned from the alloc callback.
* @get_dmabuf: acquire userspace memory for a hardware operation; used for
* DMABUF memory types.
* @get_userptr: acquire userspace memory for a hardware operation; used for
* USERPTR memory types; vaddr is the address passed to the
* videobuf layer when queuing a video buffer of USERPTR type;
* should return an allocator private per-buffer structure
* associated with the buffer on success, NULL on failure;
* the returned private structure will then be passed as buf_priv
* argument to other ops in this structure.
* @put_userptr: inform the allocator that a USERPTR buffer will no longer
* be used.
* @attach_dmabuf: attach a shared struct dma_buf for a hardware operation;
* used for DMABUF memory types; alloc_ctx is the alloc context
* dbuf is the shared dma_buf; returns NULL on failure;
* allocator private per-buffer structure on success;
* this needs to be used for further accesses to the buffer.
* @detach_dmabuf: inform the exporter of the buffer that the current DMABUF
* buffer is no longer used; the buf_priv argument is the
* allocator private per-buffer structure previously returned
* from the attach_dmabuf callback.
* @map_dmabuf: request for access to the dmabuf from allocator; the allocator
* of dmabuf is informed that this driver is going to use the
* dmabuf.
* @unmap_dmabuf: releases access control to the dmabuf - allocator is notified
* that this driver is done using the dmabuf for now.
* @prepare: called every time the buffer is passed from userspace to the
* driver, useful for cache synchronisation, optional.
* @finish: called every time the buffer is passed back from the driver
* to the userspace, also optional.
* @vaddr: return a kernel virtual address to a given memory buffer
* associated with the passed private structure or NULL if no
* such mapping exists.
* @cookie: return allocator specific cookie for a given memory buffer
* associated with the passed private structure or NULL if not
* available.
* @num_users: return the current number of users of a memory buffer;
* return 1 if the videobuf layer (or actually the driver using
* it) is the only user.
* @mmap: setup a userspace mapping for a given memory buffer under
* the provided virtual memory region.
*
* Required ops for USERPTR types: get_userptr, put_userptr.
* Required ops for MMAP types: alloc, put, num_users, mmap.
* Required ops for read/write access types: alloc, put, num_users, vaddr.
* Required ops for DMABUF types: attach_dmabuf, detach_dmabuf, map_dmabuf,
* unmap_dmabuf.
*/
struct vb2_mem_ops {
void *(*alloc)(void *alloc_ctx, unsigned long size,
enum dma_data_direction dma_dir,
gfp_t gfp_flags);
void (*put)(void *buf_priv);
struct dma_buf *(*get_dmabuf)(void *buf_priv, unsigned long flags);
void *(*get_userptr)(void *alloc_ctx, unsigned long vaddr,
unsigned long size,
enum dma_data_direction dma_dir);
void (*put_userptr)(void *buf_priv);
void (*prepare)(void *buf_priv);
void (*finish)(void *buf_priv);
void *(*attach_dmabuf)(void *alloc_ctx, struct dma_buf *dbuf,
unsigned long size,
enum dma_data_direction dma_dir);
void (*detach_dmabuf)(void *buf_priv);
int (*map_dmabuf)(void *buf_priv);
void (*unmap_dmabuf)(void *buf_priv);
void *(*vaddr)(void *buf_priv);
void *(*cookie)(void *buf_priv);
unsigned int (*num_users)(void *buf_priv);
int (*mmap)(void *buf_priv, struct vm_area_struct *vma);
};
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