cregit-Linux how code gets into the kernel

Release 4.12 include/media/videobuf-dma-sg.h

Directory: include/media
 * helper functions for SG DMA video4linux capture buffers
 * The functions expect the hardware being able to scatter gather
 * (i.e. the buffers are not linear in physical memory, but fragmented
 * into PAGE_SIZE chunks).  They also assume the driver does not need
 * to touch the video data.
 * (c) 2007 Mauro Carvalho Chehab, <>
 * Highly based on video-buf written originally by:
 * (c) 2001,02 Gerd Knorr <>
 * (c) 2006 Mauro Carvalho Chehab, <>
 * (c) 2006 Ted Walther and John Sokol
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2


#include <media/videobuf-core.h>

/* --------------------------------------------------------------------- */

 * A small set of helper functions to manage buffers (both userland
 * and kernel) for DMA.
 * videobuf_dma_init_*()
 *      creates a buffer.  The userland version takes a userspace
 *      pointer + length.  The kernel version just wants the size and
 *      does memory allocation too using vmalloc_32().
 * videobuf_dma_*()
 *      see Documentation/DMA-API-HOWTO.txt, these functions to
 *      basically the same.  The map function does also build a
 *      scatterlist for the buffer (and unmap frees it ...)
 * videobuf_dma_free()
 *      no comment ...

struct videobuf_dmabuf {
u32                 magic;

	/* for userland buffer */
int                 offset;
size_t		    size;
struct page         **pages;

	/* for kernel buffers */
void                *vaddr;
struct page         **vaddr_pages;
dma_addr_t          *dma_addr;
struct device       *dev;

	/* for overlay buffers (pci-pci dma) */
dma_addr_t          bus_addr;

	/* common */
struct scatterlist  *sglist;
int                 sglen;
int                 nr_pages;
int                 direction;

struct videobuf_dma_sg_memory {
u32                 magic;

	/* for mmap'ed buffers */
struct videobuf_dmabuf  dma;

 * Scatter-gather DMA buffer API.
 * These functions provide a simple way to create a page list and a
 * scatter-gather list from a kernel, userspace of physical address and map the
 * memory for DMA operation.
 * Despite the name, this is totally unrelated to videobuf, except that
 * videobuf-dma-sg uses the same API internally.
int videobuf_dma_free(struct videobuf_dmabuf *dma);

int videobuf_dma_unmap(struct device *dev, struct videobuf_dmabuf *dma);
struct videobuf_dmabuf *videobuf_to_dma(struct videobuf_buffer *buf);

void *videobuf_sg_alloc(size_t size);

void videobuf_queue_sg_init(struct videobuf_queue *q,
			 const struct videobuf_queue_ops *ops,
			 struct device *dev,
			 spinlock_t *irqlock,
			 enum v4l2_buf_type type,
			 enum v4l2_field field,
			 unsigned int msize,
			 void *priv,
			 struct mutex *ext_lock);

#endif /* _VIDEOBUF_DMA_SG_H */

Overall Contributors

Mauro Carvalho Chehab13275.00%19.09%
James Harper158.52%19.09%
Pawel Osciak95.11%19.09%
Hans Verkuil84.55%218.18%
Guennadi Liakhovetski52.84%19.09%
Laurent Pinchart42.27%218.18%
Jonathan Corbet10.57%19.09%
Paul Bolle10.57%19.09%
Magnus Damm10.57%19.09%
Directory: include/media
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