xref: /openbmc/linux/include/media/videobuf-dma-sg.h (revision 1faa39e0)

/* SPDX-License-Identifier: GPL-2.0-only */
/*
 * 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, <mchehab@kernel.org>
 *
 * Highly based on video-buf written originally by:
 * (c) 2001,02 Gerd Knorr <kraxel@bytesex.org>
 * (c) 2006 Mauro Carvalho Chehab, <mchehab@kernel.org>
 * (c) 2006 Ted Walther and John Sokol
 */
#ifndef _VIDEOBUF_DMA_SG_H
#define _VIDEOBUF_DMA_SG_H

#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/core-api/dma-api-howto.rst, 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;
	unsigned long       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 */