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+/* 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 */
+