media: drivers/media/common/videobuf2: rename from videobuf

This directory contains the videobuf2 framework, so name the
directory accordingly.

The name 'videobuf' typically refers to the old and deprecated
videobuf version 1 framework so that was confusing.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

1 files changed, 787 insertions, 0 deletions

diff --git a/drivers/media/common/videobuf2/videobuf2-dma-contig.c b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
new file mode 100644
index 000000000000..f1178f6f434d
--- /dev/null
+++ b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
@@ -0,0 +1,787 @@
+/*
+ * videobuf2-dma-contig.c - DMA contig memory allocator for videobuf2
+ *
+ * Copyright (C) 2010 Samsung Electronics
+ *
+ * Author: Pawel Osciak <pawel@osciak.com>
+ *
+ * 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.
+ */
+
+#include <linux/dma-buf.h>
+#include <linux/module.h>
+#include <linux/refcount.h>
+#include <linux/scatterlist.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/dma-mapping.h>
+
+#include <media/videobuf2-v4l2.h>
+#include <media/videobuf2-dma-contig.h>
+#include <media/videobuf2-memops.h>
+
+struct vb2_dc_buf {
+	struct device			*dev;
+	void				*vaddr;
+	unsigned long			size;
+	void				*cookie;
+	dma_addr_t			dma_addr;
+	unsigned long			attrs;
+	enum dma_data_direction		dma_dir;
+	struct sg_table			*dma_sgt;
+	struct frame_vector		*vec;
+
+	/* MMAP related */
+	struct vb2_vmarea_handler	handler;
+	refcount_t			refcount;
+	struct sg_table			*sgt_base;
+
+	/* DMABUF related */
+	struct dma_buf_attachment	*db_attach;
+};
+
+/*********************************************/
+/*        scatterlist table functions        */
+/*********************************************/
+
+static unsigned long vb2_dc_get_contiguous_size(struct sg_table *sgt)
+{
+	struct scatterlist *s;
+	dma_addr_t expected = sg_dma_address(sgt->sgl);
+	unsigned int i;
+	unsigned long size = 0;
+
+	for_each_sg(sgt->sgl, s, sgt->nents, i) {
+		if (sg_dma_address(s) != expected)
+			break;
+		expected = sg_dma_address(s) + sg_dma_len(s);
+		size += sg_dma_len(s);
+	}
+	return size;
+}
+
+/*********************************************/
+/*         callbacks for all buffers         */
+/*********************************************/
+
+static void *vb2_dc_cookie(void *buf_priv)
+{
+	struct vb2_dc_buf *buf = buf_priv;
+
+	return &buf->dma_addr;
+}
+
+static void *vb2_dc_vaddr(void *buf_priv)
+{
+	struct vb2_dc_buf *buf = buf_priv;
+
+	if (!buf->vaddr && buf->db_attach)
+		buf->vaddr = dma_buf_vmap(buf->db_attach->dmabuf);
+
+	return buf->vaddr;
+}
+
+static unsigned int vb2_dc_num_users(void *buf_priv)
+{
+	struct vb2_dc_buf *buf = buf_priv;
+
+	return refcount_read(&buf->refcount);
+}
+
+static void vb2_dc_prepare(void *buf_priv)
+{
+	struct vb2_dc_buf *buf = buf_priv;
+	struct sg_table *sgt = buf->dma_sgt;
+
+	/* DMABUF exporter will flush the cache for us */
+	if (!sgt || buf->db_attach)
+		return;
+
+	dma_sync_sg_for_device(buf->dev, sgt->sgl, sgt->orig_nents,
+			       buf->dma_dir);
+}
+
+static void vb2_dc_finish(void *buf_priv)
+{
+	struct vb2_dc_buf *buf = buf_priv;
+	struct sg_table *sgt = buf->dma_sgt;
+
+	/* DMABUF exporter will flush the cache for us */
+	if (!sgt || buf->db_attach)
+		return;
+
+	dma_sync_sg_for_cpu(buf->dev, sgt->sgl, sgt->orig_nents, buf->dma_dir);
+}
+
+/*********************************************/
+/*        callbacks for MMAP buffers         */
+/*********************************************/
+
+static void vb2_dc_put(void *buf_priv)
+{
+	struct vb2_dc_buf *buf = buf_priv;
+
+	if (!refcount_dec_and_test(&buf->refcount))
+		return;
+
+	if (buf->sgt_base) {
+		sg_free_table(buf->sgt_base);
+		kfree(buf->sgt_base);
+	}
+	dma_free_attrs(buf->dev, buf->size, buf->cookie, buf->dma_addr,
+		       buf->attrs);
+	put_device(buf->dev);
+	kfree(buf);
+}
+
+static void *vb2_dc_alloc(struct device *dev, unsigned long attrs,
+			  unsigned long size, enum dma_data_direction dma_dir,
+			  gfp_t gfp_flags)
+{
+	struct vb2_dc_buf *buf;
+
+	if (WARN_ON(!dev))
+		return ERR_PTR(-EINVAL);
+
+	buf = kzalloc(sizeof *buf, GFP_KERNEL);
+	if (!buf)
+		return ERR_PTR(-ENOMEM);
+
+	if (attrs)
+		buf->attrs = attrs;
+	buf->cookie = dma_alloc_attrs(dev, size, &buf->dma_addr,
+					GFP_KERNEL | gfp_flags, buf->attrs);
+	if (!buf->cookie) {
+		dev_err(dev, "dma_alloc_coherent of size %ld failed\n", size);
+		kfree(buf);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	if ((buf->attrs & DMA_ATTR_NO_KERNEL_MAPPING) == 0)
+		buf->vaddr = buf->cookie;
+
+	/* Prevent the device from being released while the buffer is used */
+	buf->dev = get_device(dev);
+	buf->size = size;
+	buf->dma_dir = dma_dir;
+
+	buf->handler.refcount = &buf->refcount;
+	buf->handler.put = vb2_dc_put;
+	buf->handler.arg = buf;
+
+	refcount_set(&buf->refcount, 1);
+
+	return buf;
+}
+
+static int vb2_dc_mmap(void *buf_priv, struct vm_area_struct *vma)
+{
+	struct vb2_dc_buf *buf = buf_priv;
+	int ret;
+
+	if (!buf) {
+		printk(KERN_ERR "No buffer to map\n");
+		return -EINVAL;
+	}
+
+	/*
+	 * dma_mmap_* uses vm_pgoff as in-buffer offset, but we want to
+	 * map whole buffer
+	 */
+	vma->vm_pgoff = 0;
+
+	ret = dma_mmap_attrs(buf->dev, vma, buf->cookie,
+		buf->dma_addr, buf->size, buf->attrs);
+
+	if (ret) {
+		pr_err("Remapping memory failed, error: %d\n", ret);
+		return ret;
+	}
+
+	vma->vm_flags		|= VM_DONTEXPAND | VM_DONTDUMP;
+	vma->vm_private_data	= &buf->handler;
+	vma->vm_ops		= &vb2_common_vm_ops;
+
+	vma->vm_ops->open(vma);
+
+	pr_debug("%s: mapped dma addr 0x%08lx at 0x%08lx, size %ld\n",
+		__func__, (unsigned long)buf->dma_addr, vma->vm_start,
+		buf->size);
+
+	return 0;
+}
+
+/*********************************************/
+/*         DMABUF ops for exporters          */
+/*********************************************/
+
+struct vb2_dc_attachment {
+	struct sg_table sgt;
+	enum dma_data_direction dma_dir;
+};
+
+static int vb2_dc_dmabuf_ops_attach(struct dma_buf *dbuf, struct device *dev,
+	struct dma_buf_attachment *dbuf_attach)
+{
+	struct vb2_dc_attachment *attach;
+	unsigned int i;
+	struct scatterlist *rd, *wr;
+	struct sg_table *sgt;
+	struct vb2_dc_buf *buf = dbuf->priv;
+	int ret;
+
+	attach = kzalloc(sizeof(*attach), GFP_KERNEL);
+	if (!attach)
+		return -ENOMEM;
+
+	sgt = &attach->sgt;
+	/* Copy the buf->base_sgt scatter list to the attachment, as we can't
+	 * map the same scatter list to multiple attachments at the same time.
+	 */
+	ret = sg_alloc_table(sgt, buf->sgt_base->orig_nents, GFP_KERNEL);
+	if (ret) {
+		kfree(attach);
+		return -ENOMEM;
+	}
+
+	rd = buf->sgt_base->sgl;
+	wr = sgt->sgl;
+	for (i = 0; i < sgt->orig_nents; ++i) {
+		sg_set_page(wr, sg_page(rd), rd->length, rd->offset);
+		rd = sg_next(rd);
+		wr = sg_next(wr);
+	}
+
+	attach->dma_dir = DMA_NONE;
+	dbuf_attach->priv = attach;
+
+	return 0;
+}
+
+static void vb2_dc_dmabuf_ops_detach(struct dma_buf *dbuf,
+	struct dma_buf_attachment *db_attach)
+{
+	struct vb2_dc_attachment *attach = db_attach->priv;
+	struct sg_table *sgt;
+
+	if (!attach)
+		return;
+
+	sgt = &attach->sgt;
+
+	/* release the scatterlist cache */
+	if (attach->dma_dir != DMA_NONE)
+		dma_unmap_sg(db_attach->dev, sgt->sgl, sgt->orig_nents,
+			attach->dma_dir);
+	sg_free_table(sgt);
+	kfree(attach);
+	db_attach->priv = NULL;
+}
+
+static struct sg_table *vb2_dc_dmabuf_ops_map(
+	struct dma_buf_attachment *db_attach, enum dma_data_direction dma_dir)
+{
+	struct vb2_dc_attachment *attach = db_attach->priv;
+	/* stealing dmabuf mutex to serialize map/unmap operations */
+	struct mutex *lock = &db_attach->dmabuf->lock;
+	struct sg_table *sgt;
+
+	mutex_lock(lock);
+
+	sgt = &attach->sgt;
+	/* return previously mapped sg table */
+	if (attach->dma_dir == dma_dir) {
+		mutex_unlock(lock);
+		return sgt;
+	}
+
+	/* release any previous cache */
+	if (attach->dma_dir != DMA_NONE) {
+		dma_unmap_sg(db_attach->dev, sgt->sgl, sgt->orig_nents,
+			attach->dma_dir);
+		attach->dma_dir = DMA_NONE;
+	}
+
+	/* mapping to the client with new direction */
+	sgt->nents = dma_map_sg(db_attach->dev, sgt->sgl, sgt->orig_nents,
+				dma_dir);
+	if (!sgt->nents) {
+		pr_err("failed to map scatterlist\n");
+		mutex_unlock(lock);
+		return ERR_PTR(-EIO);
+	}
+
+	attach->dma_dir = dma_dir;
+
+	mutex_unlock(lock);
+
+	return sgt;
+}
+
+static void vb2_dc_dmabuf_ops_unmap(struct dma_buf_attachment *db_attach,
+	struct sg_table *sgt, enum dma_data_direction dma_dir)
+{
+	/* nothing to be done here */
+}
+
+static void vb2_dc_dmabuf_ops_release(struct dma_buf *dbuf)
+{
+	/* drop reference obtained in vb2_dc_get_dmabuf */
+	vb2_dc_put(dbuf->priv);
+}
+
+static void *vb2_dc_dmabuf_ops_kmap(struct dma_buf *dbuf, unsigned long pgnum)
+{
+	struct vb2_dc_buf *buf = dbuf->priv;
+
+	return buf->vaddr ? buf->vaddr + pgnum * PAGE_SIZE : NULL;
+}
+
+static void *vb2_dc_dmabuf_ops_vmap(struct dma_buf *dbuf)
+{
+	struct vb2_dc_buf *buf = dbuf->priv;
+
+	return buf->vaddr;
+}
+
+static int vb2_dc_dmabuf_ops_mmap(struct dma_buf *dbuf,
+	struct vm_area_struct *vma)
+{
+	return vb2_dc_mmap(dbuf->priv, vma);
+}
+
+static const struct dma_buf_ops vb2_dc_dmabuf_ops = {
+	.attach = vb2_dc_dmabuf_ops_attach,
+	.detach = vb2_dc_dmabuf_ops_detach,
+	.map_dma_buf = vb2_dc_dmabuf_ops_map,
+	.unmap_dma_buf = vb2_dc_dmabuf_ops_unmap,
+	.map = vb2_dc_dmabuf_ops_kmap,
+	.map_atomic = vb2_dc_dmabuf_ops_kmap,
+	.vmap = vb2_dc_dmabuf_ops_vmap,
+	.mmap = vb2_dc_dmabuf_ops_mmap,
+	.release = vb2_dc_dmabuf_ops_release,
+};
+
+static struct sg_table *vb2_dc_get_base_sgt(struct vb2_dc_buf *buf)
+{
+	int ret;
+	struct sg_table *sgt;
+
+	sgt = kmalloc(sizeof(*sgt), GFP_KERNEL);
+	if (!sgt) {
+		dev_err(buf->dev, "failed to alloc sg table\n");
+		return NULL;
+	}
+
+	ret = dma_get_sgtable_attrs(buf->dev, sgt, buf->cookie, buf->dma_addr,
+		buf->size, buf->attrs);
+	if (ret < 0) {
+		dev_err(buf->dev, "failed to get scatterlist from DMA API\n");
+		kfree(sgt);
+		return NULL;
+	}
+
+	return sgt;
+}
+
+static struct dma_buf *vb2_dc_get_dmabuf(void *buf_priv, unsigned long flags)
+{
+	struct vb2_dc_buf *buf = buf_priv;
+	struct dma_buf *dbuf;
+	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
+
+	exp_info.ops = &vb2_dc_dmabuf_ops;
+	exp_info.size = buf->size;
+	exp_info.flags = flags;
+	exp_info.priv = buf;
+
+	if (!buf->sgt_base)
+		buf->sgt_base = vb2_dc_get_base_sgt(buf);
+
+	if (WARN_ON(!buf->sgt_base))
+		return NULL;
+
+	dbuf = dma_buf_export(&exp_info);
+	if (IS_ERR(dbuf))
+		return NULL;
+
+	/* dmabuf keeps reference to vb2 buffer */
+	refcount_inc(&buf->refcount);
+
+	return dbuf;
+}
+
+/*********************************************/
+/*       callbacks for USERPTR buffers       */
+/*********************************************/
+
+static void vb2_dc_put_userptr(void *buf_priv)
+{
+	struct vb2_dc_buf *buf = buf_priv;
+	struct sg_table *sgt = buf->dma_sgt;
+	int i;
+	struct page **pages;
+
+	if (sgt) {
+		/*
+		 * No need to sync to CPU, it's already synced to the CPU
+		 * since the finish() memop will have been called before this.
+		 */
+		dma_unmap_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents,
+				   buf->dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
+		pages = frame_vector_pages(buf->vec);
+		/* sgt should exist only if vector contains pages... */
+		BUG_ON(IS_ERR(pages));
+		if (buf->dma_dir == DMA_FROM_DEVICE ||
+		    buf->dma_dir == DMA_BIDIRECTIONAL)
+			for (i = 0; i < frame_vector_count(buf->vec); i++)
+				set_page_dirty_lock(pages[i]);
+		sg_free_table(sgt);
+		kfree(sgt);
+	}
+	vb2_destroy_framevec(buf->vec);
+	kfree(buf);
+}
+
+/*
+ * For some kind of reserved memory there might be no struct page available,
+ * so all that can be done to support such 'pages' is to try to convert
+ * pfn to dma address or at the last resort just assume that
+ * dma address == physical address (like it has been assumed in earlier version
+ * of videobuf2-dma-contig
+ */
+
+#ifdef __arch_pfn_to_dma
+static inline dma_addr_t vb2_dc_pfn_to_dma(struct device *dev, unsigned long pfn)
+{
+	return (dma_addr_t)__arch_pfn_to_dma(dev, pfn);
+}
+#elif defined(__pfn_to_bus)
+static inline dma_addr_t vb2_dc_pfn_to_dma(struct device *dev, unsigned long pfn)
+{
+	return (dma_addr_t)__pfn_to_bus(pfn);
+}
+#elif defined(__pfn_to_phys)
+static inline dma_addr_t vb2_dc_pfn_to_dma(struct device *dev, unsigned long pfn)
+{
+	return (dma_addr_t)__pfn_to_phys(pfn);
+}
+#else
+static inline dma_addr_t vb2_dc_pfn_to_dma(struct device *dev, unsigned long pfn)
+{
+	/* really, we cannot do anything better at this point */
+	return (dma_addr_t)(pfn) << PAGE_SHIFT;
+}
+#endif
+
+static void *vb2_dc_get_userptr(struct device *dev, unsigned long vaddr,
+	unsigned long size, enum dma_data_direction dma_dir)
+{
+	struct vb2_dc_buf *buf;
+	struct frame_vector *vec;
+	unsigned int offset;
+	int n_pages, i;
+	int ret = 0;
+	struct sg_table *sgt;
+	unsigned long contig_size;
+	unsigned long dma_align = dma_get_cache_alignment();
+
+	/* Only cache aligned DMA transfers are reliable */
+	if (!IS_ALIGNED(vaddr | size, dma_align)) {
+		pr_debug("user data must be aligned to %lu bytes\n", dma_align);
+		return ERR_PTR(-EINVAL);
+	}
+
+	if (!size) {
+		pr_debug("size is zero\n");
+		return ERR_PTR(-EINVAL);
+	}
+
+	if (WARN_ON(!dev))
+		return ERR_PTR(-EINVAL);
+
+	buf = kzalloc(sizeof *buf, GFP_KERNEL);
+	if (!buf)
+		return ERR_PTR(-ENOMEM);
+
+	buf->dev = dev;
+	buf->dma_dir = dma_dir;
+
+	offset = lower_32_bits(offset_in_page(vaddr));
+	vec = vb2_create_framevec(vaddr, size, dma_dir == DMA_FROM_DEVICE ||
+					       dma_dir == DMA_BIDIRECTIONAL);
+	if (IS_ERR(vec)) {
+		ret = PTR_ERR(vec);
+		goto fail_buf;
+	}
+	buf->vec = vec;
+	n_pages = frame_vector_count(vec);
+	ret = frame_vector_to_pages(vec);
+	if (ret < 0) {
+		unsigned long *nums = frame_vector_pfns(vec);
+
+		/*
+		 * Failed to convert to pages... Check the memory is physically
+		 * contiguous and use direct mapping
+		 */
+		for (i = 1; i < n_pages; i++)
+			if (nums[i-1] + 1 != nums[i])
+				goto fail_pfnvec;
+		buf->dma_addr = vb2_dc_pfn_to_dma(buf->dev, nums[0]);
+		goto out;
+	}
+
+	sgt = kzalloc(sizeof(*sgt), GFP_KERNEL);
+	if (!sgt) {
+		pr_err("failed to allocate sg table\n");
+		ret = -ENOMEM;
+		goto fail_pfnvec;
+	}
+
+	ret = sg_alloc_table_from_pages(sgt, frame_vector_pages(vec), n_pages,
+		offset, size, GFP_KERNEL);
+	if (ret) {
+		pr_err("failed to initialize sg table\n");
+		goto fail_sgt;
+	}
+
+	/*
+	 * No need to sync to the device, this will happen later when the
+	 * prepare() memop is called.
+	 */
+	sgt->nents = dma_map_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents,
+				      buf->dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
+	if (sgt->nents <= 0) {
+		pr_err("failed to map scatterlist\n");
+		ret = -EIO;
+		goto fail_sgt_init;
+	}
+
+	contig_size = vb2_dc_get_contiguous_size(sgt);
+	if (contig_size < size) {
+		pr_err("contiguous mapping is too small %lu/%lu\n",
+			contig_size, size);
+		ret = -EFAULT;
+		goto fail_map_sg;
+	}
+
+	buf->dma_addr = sg_dma_address(sgt->sgl);
+	buf->dma_sgt = sgt;
+out:
+	buf->size = size;
+
+	return buf;
+
+fail_map_sg:
+	dma_unmap_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents,
+			   buf->dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
+
+fail_sgt_init:
+	sg_free_table(sgt);
+
+fail_sgt:
+	kfree(sgt);
+
+fail_pfnvec:
+	vb2_destroy_framevec(vec);
+
+fail_buf:
+	kfree(buf);
+
+	return ERR_PTR(ret);
+}
+
+/*********************************************/
+/*       callbacks for DMABUF buffers        */
+/*********************************************/
+
+static int vb2_dc_map_dmabuf(void *mem_priv)
+{
+	struct vb2_dc_buf *buf = mem_priv;
+	struct sg_table *sgt;
+	unsigned long contig_size;
+
+	if (WARN_ON(!buf->db_attach)) {
+		pr_err("trying to pin a non attached buffer\n");
+		return -EINVAL;
+	}
+
+	if (WARN_ON(buf->dma_sgt)) {
+		pr_err("dmabuf buffer is already pinned\n");
+		return 0;
+	}
+
+	/* get the associated scatterlist for this buffer */
+	sgt = dma_buf_map_attachment(buf->db_attach, buf->dma_dir);
+	if (IS_ERR(sgt)) {
+		pr_err("Error getting dmabuf scatterlist\n");
+		return -EINVAL;
+	}
+
+	/* checking if dmabuf is big enough to store contiguous chunk */
+	contig_size = vb2_dc_get_contiguous_size(sgt);
+	if (contig_size < buf->size) {
+		pr_err("contiguous chunk is too small %lu/%lu b\n",
+			contig_size, buf->size);
+		dma_buf_unmap_attachment(buf->db_attach, sgt, buf->dma_dir);
+		return -EFAULT;
+	}
+
+	buf->dma_addr = sg_dma_address(sgt->sgl);
+	buf->dma_sgt = sgt;
+	buf->vaddr = NULL;
+
+	return 0;
+}
+
+static void vb2_dc_unmap_dmabuf(void *mem_priv)
+{
+	struct vb2_dc_buf *buf = mem_priv;
+	struct sg_table *sgt = buf->dma_sgt;
+
+	if (WARN_ON(!buf->db_attach)) {
+		pr_err("trying to unpin a not attached buffer\n");
+		return;
+	}
+
+	if (WARN_ON(!sgt)) {
+		pr_err("dmabuf buffer is already unpinned\n");
+		return;
+	}
+
+	if (buf->vaddr) {
+		dma_buf_vunmap(buf->db_attach->dmabuf, buf->vaddr);
+		buf->vaddr = NULL;
+	}
+	dma_buf_unmap_attachment(buf->db_attach, sgt, buf->dma_dir);
+
+	buf->dma_addr = 0;
+	buf->dma_sgt = NULL;
+}
+
+static void vb2_dc_detach_dmabuf(void *mem_priv)
+{
+	struct vb2_dc_buf *buf = mem_priv;
+
+	/* if vb2 works correctly you should never detach mapped buffer */
+	if (WARN_ON(buf->dma_addr))
+		vb2_dc_unmap_dmabuf(buf);
+
+	/* detach this attachment */
+	dma_buf_detach(buf->db_attach->dmabuf, buf->db_attach);
+	kfree(buf);
+}
+
+static void *vb2_dc_attach_dmabuf(struct device *dev, struct dma_buf *dbuf,
+	unsigned long size, enum dma_data_direction dma_dir)
+{
+	struct vb2_dc_buf *buf;
+	struct dma_buf_attachment *dba;
+
+	if (dbuf->size < size)
+		return ERR_PTR(-EFAULT);
+
+	if (WARN_ON(!dev))
+		return ERR_PTR(-EINVAL);
+
+	buf = kzalloc(sizeof(*buf), GFP_KERNEL);
+	if (!buf)
+		return ERR_PTR(-ENOMEM);
+
+	buf->dev = dev;
+	/* create attachment for the dmabuf with the user device */
+	dba = dma_buf_attach(dbuf, buf->dev);
+	if (IS_ERR(dba)) {
+		pr_err("failed to attach dmabuf\n");
+		kfree(buf);
+		return dba;
+	}
+
+	buf->dma_dir = dma_dir;
+	buf->size = size;
+	buf->db_attach = dba;
+
+	return buf;
+}
+
+/*********************************************/
+/*       DMA CONTIG exported functions       */
+/*********************************************/
+
+const struct vb2_mem_ops vb2_dma_contig_memops = {
+	.alloc		= vb2_dc_alloc,
+	.put		= vb2_dc_put,
+	.get_dmabuf	= vb2_dc_get_dmabuf,
+	.cookie		= vb2_dc_cookie,
+	.vaddr		= vb2_dc_vaddr,
+	.mmap		= vb2_dc_mmap,
+	.get_userptr	= vb2_dc_get_userptr,
+	.put_userptr	= vb2_dc_put_userptr,
+	.prepare	= vb2_dc_prepare,
+	.finish		= vb2_dc_finish,
+	.map_dmabuf	= vb2_dc_map_dmabuf,
+	.unmap_dmabuf	= vb2_dc_unmap_dmabuf,
+	.attach_dmabuf	= vb2_dc_attach_dmabuf,
+	.detach_dmabuf	= vb2_dc_detach_dmabuf,
+	.num_users	= vb2_dc_num_users,
+};
+EXPORT_SYMBOL_GPL(vb2_dma_contig_memops);
+
+/**
+ * vb2_dma_contig_set_max_seg_size() - configure DMA max segment size
+ * @dev:	device for configuring DMA parameters
+ * @size:	size of DMA max segment size to set
+ *
+ * To allow mapping the scatter-list into a single chunk in the DMA
+ * address space, the device is required to have the DMA max segment
+ * size parameter set to a value larger than the buffer size. Otherwise,
+ * the DMA-mapping subsystem will split the mapping into max segment
+ * size chunks. This function sets the DMA max segment size
+ * parameter to let DMA-mapping map a buffer as a single chunk in DMA
+ * address space.
+ * This code assumes that the DMA-mapping subsystem will merge all
+ * scatterlist segments if this is really possible (for example when
+ * an IOMMU is available and enabled).
+ * Ideally, this parameter should be set by the generic bus code, but it
+ * is left with the default 64KiB value due to historical litmiations in
+ * other subsystems (like limited USB host drivers) and there no good
+ * place to set it to the proper value.
+ * This function should be called from the drivers, which are known to
+ * operate on platforms with IOMMU and provide access to shared buffers
+ * (either USERPTR or DMABUF). This should be done before initializing
+ * videobuf2 queue.
+ */
+int vb2_dma_contig_set_max_seg_size(struct device *dev, unsigned int size)
+{
+	if (!dev->dma_parms) {
+		dev->dma_parms = kzalloc(sizeof(*dev->dma_parms), GFP_KERNEL);
+		if (!dev->dma_parms)
+			return -ENOMEM;
+	}
+	if (dma_get_max_seg_size(dev) < size)
+		return dma_set_max_seg_size(dev, size);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(vb2_dma_contig_set_max_seg_size);
+
+/*
+ * vb2_dma_contig_clear_max_seg_size() - release resources for DMA parameters
+ * @dev:	device for configuring DMA parameters
+ *
+ * This function releases resources allocated to configure DMA parameters
+ * (see vb2_dma_contig_set_max_seg_size() function). It should be called from
+ * device drivers on driver remove.
+ */
+void vb2_dma_contig_clear_max_seg_size(struct device *dev)
+{
+	kfree(dev->dma_parms);
+	dev->dma_parms = NULL;
+}
+EXPORT_SYMBOL_GPL(vb2_dma_contig_clear_max_seg_size);
+
+MODULE_DESCRIPTION("DMA-contig memory handling routines for videobuf2");
+MODULE_AUTHOR("Pawel Osciak <pawel@osciak.com>");
+MODULE_LICENSE("GPL");