drivers/media/v4l2-core/videobuf2-dma-sg.c - kernel/msm-5.4 - Gitiles

 /*
  * videobuf2-dma-sg.c - dma scatter/gather memory allocator for videobuf2
  *
  * Copyright (C) 2010 Samsung Electronics
  *
  * Author: Andrzej Pietrasiewicz <andrzej.p@samsung.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/module.h>
 #include <linux/mm.h>
 #include <linux/scatterlist.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/vmalloc.h>

 #include <media/videobuf2-core.h>
 #include <media/videobuf2-memops.h>
 #include <media/videobuf2-dma-sg.h>

 static int debug;
 module_param(debug, int, 0644);

 #define dprintk(level, fmt, arg...)					\
 	do {								\
 		if (debug >= level)					\
 			printk(KERN_DEBUG "vb2-dma-sg: " fmt, ## arg);	\
 	} while (0)

 struct vb2_dma_sg_conf {
 	struct device		*dev;
 };

 struct vb2_dma_sg_buf {
 	struct device			*dev;
 	void				*vaddr;
 	struct page			**pages;
 	int				offset;
 	enum dma_data_direction		dma_dir;
 	struct sg_table			sg_table;
 	/*
 	 * This will point to sg_table when used with the MMAP or USERPTR
 	 * memory model, and to the dma_buf sglist when used with the
 	 * DMABUF memory model.
 	 */
 	struct sg_table			*dma_sgt;
 	size_t				size;
 	unsigned int			num_pages;
 	atomic_t			refcount;
 	struct vb2_vmarea_handler	handler;
 	struct vm_area_struct		*vma;

 	struct dma_buf_attachment	*db_attach;
 };

 static void vb2_dma_sg_put(void *buf_priv);

 static int vb2_dma_sg_alloc_compacted(struct vb2_dma_sg_buf *buf,
 		gfp_t gfp_flags)
 {
 	unsigned int last_page = 0;
 	int size = buf->size;

 	while (size > 0) {
 		struct page *pages;
 		int order;
 		int i;

 		order = get_order(size);
 		/* Dont over allocate*/
 		if ((PAGE_SIZE << order) > size)
 			order--;

 		pages = NULL;
 		while (!pages) {
 			pages = alloc_pages(GFP_KERNEL | __GFP_ZERO |
 					__GFP_NOWARN | gfp_flags, order);
 			if (pages)
 				break;

 			if (order == 0) {
 				while (last_page--)
 					__free_page(buf->pages[last_page]);
 				return -ENOMEM;
 			}
 			order--;
 		}

 		split_page(pages, order);
 		for (i = 0; i < (1 << order); i++)
 			buf->pages[last_page++] = &pages[i];

 		size -= PAGE_SIZE << order;
 	}

 	return 0;
 }

 static void *vb2_dma_sg_alloc(void *alloc_ctx, unsigned long size,
 			      enum dma_data_direction dma_dir, gfp_t gfp_flags)
 {
 	struct vb2_dma_sg_conf *conf = alloc_ctx;
 	struct vb2_dma_sg_buf *buf;
 	struct sg_table *sgt;
 	int ret;
 	int num_pages;
 	DEFINE_DMA_ATTRS(attrs);

 	dma_set_attr(DMA_ATTR_SKIP_CPU_SYNC, &attrs);

 	if (WARN_ON(alloc_ctx == NULL))
 		return NULL;
 	buf = kzalloc(sizeof *buf, GFP_KERNEL);
 	if (!buf)
 		return NULL;

 	buf->vaddr = NULL;
 	buf->dma_dir = dma_dir;
 	buf->offset = 0;
 	buf->size = size;
 	/* size is already page aligned */
 	buf->num_pages = size >> PAGE_SHIFT;
 	buf->dma_sgt = &buf->sg_table;

 	buf->pages = kzalloc(buf->num_pages * sizeof(struct page *),
 			     GFP_KERNEL);
 	if (!buf->pages)
 		goto fail_pages_array_alloc;

 	ret = vb2_dma_sg_alloc_compacted(buf, gfp_flags);
 	if (ret)
 		goto fail_pages_alloc;

 	ret = sg_alloc_table_from_pages(buf->dma_sgt, buf->pages,
 			buf->num_pages, 0, size, GFP_KERNEL);
 	if (ret)
 		goto fail_table_alloc;

 	/* Prevent the device from being released while the buffer is used */
 	buf->dev = get_device(conf->dev);

 	sgt = &buf->sg_table;
 	/*
 	 * 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, &attrs);
 	if (!sgt->nents)
 		goto fail_map;

 	buf->handler.refcount = &buf->refcount;
 	buf->handler.put = vb2_dma_sg_put;
 	buf->handler.arg = buf;

 	atomic_inc(&buf->refcount);

 	dprintk(1, "%s: Allocated buffer of %d pages\n",
 		__func__, buf->num_pages);
 	return buf;

 fail_map:
 	put_device(buf->dev);
 	sg_free_table(buf->dma_sgt);
 fail_table_alloc:
 	num_pages = buf->num_pages;
 	while (num_pages--)
 		__free_page(buf->pages[num_pages]);
 fail_pages_alloc:
 	kfree(buf->pages);
 fail_pages_array_alloc:
 	kfree(buf);
 	return NULL;
 }

 static void vb2_dma_sg_put(void *buf_priv)
 {
 	struct vb2_dma_sg_buf *buf = buf_priv;
 	struct sg_table *sgt = &buf->sg_table;
 	int i = buf->num_pages;

 	if (atomic_dec_and_test(&buf->refcount)) {
 		DEFINE_DMA_ATTRS(attrs);

 		dma_set_attr(DMA_ATTR_SKIP_CPU_SYNC, &attrs);
 		dprintk(1, "%s: Freeing buffer of %d pages\n", __func__,
 			buf->num_pages);
 		dma_unmap_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents,
 				   buf->dma_dir, &attrs);
 		if (buf->vaddr)
 			vm_unmap_ram(buf->vaddr, buf->num_pages);
 		sg_free_table(buf->dma_sgt);
 		while (--i >= 0)
 			__free_page(buf->pages[i]);
 		kfree(buf->pages);
 		put_device(buf->dev);
 		kfree(buf);
 	}
 }

 static void vb2_dma_sg_prepare(void *buf_priv)
 {
 	struct vb2_dma_sg_buf *buf = buf_priv;
 	struct sg_table *sgt = buf->dma_sgt;

 	/* DMABUF exporter will flush the cache for us */
 	if (buf->db_attach)
 		return;

 	dma_sync_sg_for_device(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);
 }

 static void vb2_dma_sg_finish(void *buf_priv)
 {
 	struct vb2_dma_sg_buf *buf = buf_priv;
 	struct sg_table *sgt = buf->dma_sgt;

 	/* DMABUF exporter will flush the cache for us */
 	if (buf->db_attach)
 		return;

 	dma_sync_sg_for_cpu(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);
 }

 static inline int vma_is_io(struct vm_area_struct *vma)
 {
 	return !!(vma->vm_flags & (VM_IO | VM_PFNMAP));
 }

 static void *vb2_dma_sg_get_userptr(void *alloc_ctx, unsigned long vaddr,
 				    unsigned long size,
 				    enum dma_data_direction dma_dir)
 {
 	struct vb2_dma_sg_conf *conf = alloc_ctx;
 	struct vb2_dma_sg_buf *buf;
 	unsigned long first, last;
 	int num_pages_from_user;
 	struct vm_area_struct *vma;
 	struct sg_table *sgt;
 	DEFINE_DMA_ATTRS(attrs);

 	dma_set_attr(DMA_ATTR_SKIP_CPU_SYNC, &attrs);

 	buf = kzalloc(sizeof *buf, GFP_KERNEL);
 	if (!buf)
 		return NULL;

 	buf->vaddr = NULL;
 	buf->dev = conf->dev;
 	buf->dma_dir = dma_dir;
 	buf->offset = vaddr & ~PAGE_MASK;
 	buf->size = size;
 	buf->dma_sgt = &buf->sg_table;

 	first = (vaddr           & PAGE_MASK) >> PAGE_SHIFT;
 	last  = ((vaddr + size - 1) & PAGE_MASK) >> PAGE_SHIFT;
 	buf->num_pages = last - first + 1;

 	buf->pages = kzalloc(buf->num_pages * sizeof(struct page *),
 			     GFP_KERNEL);
 	if (!buf->pages)
 		goto userptr_fail_alloc_pages;

 	vma = find_vma(current->mm, vaddr);
 	if (!vma) {
 		dprintk(1, "no vma for address %lu\n", vaddr);
 		goto userptr_fail_find_vma;
 	}

 	if (vma->vm_end < vaddr + size) {
 		dprintk(1, "vma at %lu is too small for %lu bytes\n",
 			vaddr, size);
 		goto userptr_fail_find_vma;
 	}

 	buf->vma = vb2_get_vma(vma);
 	if (!buf->vma) {
 		dprintk(1, "failed to copy vma\n");
 		goto userptr_fail_find_vma;
 	}

 	if (vma_is_io(buf->vma)) {
 		for (num_pages_from_user = 0;
 		     num_pages_from_user < buf->num_pages;
 		     ++num_pages_from_user, vaddr += PAGE_SIZE) {
 			unsigned long pfn;

 			if (follow_pfn(vma, vaddr, &pfn)) {
 				dprintk(1, "no page for address %lu\n", vaddr);
 				break;
 			}
 			buf->pages[num_pages_from_user] = pfn_to_page(pfn);
 		}
 	} else
 		num_pages_from_user = get_user_pages(current, current->mm,
 					     vaddr & PAGE_MASK,
 					     buf->num_pages,
 					     buf->dma_dir == DMA_FROM_DEVICE,
 					     1, /* force */
 					     buf->pages,
 					     NULL);

 	if (num_pages_from_user != buf->num_pages)
 		goto userptr_fail_get_user_pages;

 	if (sg_alloc_table_from_pages(buf->dma_sgt, buf->pages,
 			buf->num_pages, buf->offset, size, 0))
 		goto userptr_fail_alloc_table_from_pages;

 	sgt = &buf->sg_table;
 	/*
 	 * 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, &attrs);
 	if (!sgt->nents)
 		goto userptr_fail_map;

 	return buf;

 userptr_fail_map:
 	sg_free_table(&buf->sg_table);
 userptr_fail_alloc_table_from_pages:
 userptr_fail_get_user_pages:
 	dprintk(1, "get_user_pages requested/got: %d/%d]\n",
 		buf->num_pages, num_pages_from_user);
 	if (!vma_is_io(buf->vma))
 		while (--num_pages_from_user >= 0)
 			put_page(buf->pages[num_pages_from_user]);
 	vb2_put_vma(buf->vma);
 userptr_fail_find_vma:
 	kfree(buf->pages);
 userptr_fail_alloc_pages:
 	kfree(buf);
 	return NULL;
 }

 /*
  * @put_userptr: inform the allocator that a USERPTR buffer will no longer
  *		 be used
  */
 static void vb2_dma_sg_put_userptr(void *buf_priv)
 {
 	struct vb2_dma_sg_buf *buf = buf_priv;
 	struct sg_table *sgt = &buf->sg_table;
 	int i = buf->num_pages;
 	DEFINE_DMA_ATTRS(attrs);

 	dma_set_attr(DMA_ATTR_SKIP_CPU_SYNC, &attrs);

 	dprintk(1, "%s: Releasing userspace buffer of %d pages\n",
 	       __func__, buf->num_pages);
 	dma_unmap_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents, buf->dma_dir,
 			   &attrs);
 	if (buf->vaddr)
 		vm_unmap_ram(buf->vaddr, buf->num_pages);
 	sg_free_table(buf->dma_sgt);
 	while (--i >= 0) {
 		if (buf->dma_dir == DMA_FROM_DEVICE)
 			set_page_dirty_lock(buf->pages[i]);
 		if (!vma_is_io(buf->vma))
 			put_page(buf->pages[i]);
 	}
 	kfree(buf->pages);
 	vb2_put_vma(buf->vma);
 	kfree(buf);
 }

 static void *vb2_dma_sg_vaddr(void *buf_priv)
 {
 	struct vb2_dma_sg_buf *buf = buf_priv;

 	BUG_ON(!buf);

 	if (!buf->vaddr) {
 		if (buf->db_attach)
 			buf->vaddr = dma_buf_vmap(buf->db_attach->dmabuf);
 		else
 			buf->vaddr = vm_map_ram(buf->pages,
 					buf->num_pages, -1, PAGE_KERNEL);
 	}

 	/* add offset in case userptr is not page-aligned */
 	return buf->vaddr ? buf->vaddr + buf->offset : NULL;
 }

 static unsigned int vb2_dma_sg_num_users(void *buf_priv)
 {
 	struct vb2_dma_sg_buf *buf = buf_priv;

 	return atomic_read(&buf->refcount);
 }

 static int vb2_dma_sg_mmap(void *buf_priv, struct vm_area_struct *vma)
 {
 	struct vb2_dma_sg_buf *buf = buf_priv;
 	unsigned long uaddr = vma->vm_start;
 	unsigned long usize = vma->vm_end - vma->vm_start;
 	int i = 0;

 	if (!buf) {
 		printk(KERN_ERR "No memory to map\n");
 		return -EINVAL;
 	}

 	do {
 		int ret;

 		ret = vm_insert_page(vma, uaddr, buf->pages[i++]);
 		if (ret) {
 			printk(KERN_ERR "Remapping memory, error: %d\n", ret);
 			return ret;
 		}

 		uaddr += PAGE_SIZE;
 		usize -= PAGE_SIZE;
 	} while (usize > 0);


 	/*
 	 * Use common vm_area operations to track buffer refcount.
 	 */
 	vma->vm_private_data	= &buf->handler;
 	vma->vm_ops		= &vb2_common_vm_ops;

 	vma->vm_ops->open(vma);

 	return 0;
 }

 /*********************************************/
 /*         DMABUF ops for exporters          */
 /*********************************************/

 struct vb2_dma_sg_attachment {
 	struct sg_table sgt;
 	enum dma_data_direction dma_dir;
 };

 static int vb2_dma_sg_dmabuf_ops_attach(struct dma_buf *dbuf, struct device *dev,
 	struct dma_buf_attachment *dbuf_attach)
 {
 	struct vb2_dma_sg_attachment *attach;
 	unsigned int i;
 	struct scatterlist *rd, *wr;
 	struct sg_table *sgt;
 	struct vb2_dma_sg_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->dma_sgt->orig_nents, GFP_KERNEL);
 	if (ret) {
 		kfree(attach);
 		return -ENOMEM;
 	}

 	rd = buf->dma_sgt->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_dma_sg_dmabuf_ops_detach(struct dma_buf *dbuf,
 	struct dma_buf_attachment *db_attach)
 {
 	struct vb2_dma_sg_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_dma_sg_dmabuf_ops_map(
 	struct dma_buf_attachment *db_attach, enum dma_data_direction dma_dir)
 {
 	struct vb2_dma_sg_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_dma_sg_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_dma_sg_dmabuf_ops_release(struct dma_buf *dbuf)
 {
 	/* drop reference obtained in vb2_dma_sg_get_dmabuf */
 	vb2_dma_sg_put(dbuf->priv);
 }

 static void *vb2_dma_sg_dmabuf_ops_kmap(struct dma_buf *dbuf, unsigned long pgnum)
 {
 	struct vb2_dma_sg_buf *buf = dbuf->priv;

 	return buf->vaddr ? buf->vaddr + pgnum * PAGE_SIZE : NULL;
 }

 static void *vb2_dma_sg_dmabuf_ops_vmap(struct dma_buf *dbuf)
 {
 	struct vb2_dma_sg_buf *buf = dbuf->priv;

 	return vb2_dma_sg_vaddr(buf);
 }

 static int vb2_dma_sg_dmabuf_ops_mmap(struct dma_buf *dbuf,
 	struct vm_area_struct *vma)
 {
 	return vb2_dma_sg_mmap(dbuf->priv, vma);
 }

 static struct dma_buf_ops vb2_dma_sg_dmabuf_ops = {
 	.attach = vb2_dma_sg_dmabuf_ops_attach,
 	.detach = vb2_dma_sg_dmabuf_ops_detach,
 	.map_dma_buf = vb2_dma_sg_dmabuf_ops_map,
 	.unmap_dma_buf = vb2_dma_sg_dmabuf_ops_unmap,
 	.kmap = vb2_dma_sg_dmabuf_ops_kmap,
 	.kmap_atomic = vb2_dma_sg_dmabuf_ops_kmap,
 	.vmap = vb2_dma_sg_dmabuf_ops_vmap,
 	.mmap = vb2_dma_sg_dmabuf_ops_mmap,
 	.release = vb2_dma_sg_dmabuf_ops_release,
 };

 static struct dma_buf *vb2_dma_sg_get_dmabuf(void *buf_priv, unsigned long flags)
 {
 	struct vb2_dma_sg_buf *buf = buf_priv;
 	struct dma_buf *dbuf;
 	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);

 	exp_info.ops = &vb2_dma_sg_dmabuf_ops;
 	exp_info.size = buf->size;
 	exp_info.flags = flags;
 	exp_info.priv = buf;

 	if (WARN_ON(!buf->dma_sgt))
 		return NULL;

 	dbuf = dma_buf_export(&exp_info);
 	if (IS_ERR(dbuf))
 		return NULL;

 	/* dmabuf keeps reference to vb2 buffer */
 	atomic_inc(&buf->refcount);

 	return dbuf;
 }

 /*********************************************/
 /*       callbacks for DMABUF buffers        */
 /*********************************************/

 static int vb2_dma_sg_map_dmabuf(void *mem_priv)
 {
 	struct vb2_dma_sg_buf *buf = mem_priv;
 	struct sg_table *sgt;

 	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;
 	}

 	buf->dma_sgt = sgt;
 	buf->vaddr = NULL;

 	return 0;
 }

 static void vb2_dma_sg_unmap_dmabuf(void *mem_priv)
 {
 	struct vb2_dma_sg_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_sgt = NULL;
 }

 static void vb2_dma_sg_detach_dmabuf(void *mem_priv)
 {
 	struct vb2_dma_sg_buf *buf = mem_priv;

 	/* if vb2 works correctly you should never detach mapped buffer */
 	if (WARN_ON(buf->dma_sgt))
 		vb2_dma_sg_unmap_dmabuf(buf);

 	/* detach this attachment */
 	dma_buf_detach(buf->db_attach->dmabuf, buf->db_attach);
 	kfree(buf);
 }

 static void *vb2_dma_sg_attach_dmabuf(void *alloc_ctx, struct dma_buf *dbuf,
 	unsigned long size, enum dma_data_direction dma_dir)
 {
 	struct vb2_dma_sg_conf *conf = alloc_ctx;
 	struct vb2_dma_sg_buf *buf;
 	struct dma_buf_attachment *dba;

 	if (dbuf->size < size)
 		return ERR_PTR(-EFAULT);

 	buf = kzalloc(sizeof(*buf), GFP_KERNEL);
 	if (!buf)
 		return ERR_PTR(-ENOMEM);

 	buf->dev = conf->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;
 }

 static void *vb2_dma_sg_cookie(void *buf_priv)
 {
 	struct vb2_dma_sg_buf *buf = buf_priv;

 	return buf->dma_sgt;
 }

 const struct vb2_mem_ops vb2_dma_sg_memops = {
 	.alloc		= vb2_dma_sg_alloc,
 	.put		= vb2_dma_sg_put,
 	.get_userptr	= vb2_dma_sg_get_userptr,
 	.put_userptr	= vb2_dma_sg_put_userptr,
 	.prepare	= vb2_dma_sg_prepare,
 	.finish		= vb2_dma_sg_finish,
 	.vaddr		= vb2_dma_sg_vaddr,
 	.mmap		= vb2_dma_sg_mmap,
 	.num_users	= vb2_dma_sg_num_users,
 	.get_dmabuf	= vb2_dma_sg_get_dmabuf,
 	.map_dmabuf	= vb2_dma_sg_map_dmabuf,
 	.unmap_dmabuf	= vb2_dma_sg_unmap_dmabuf,
 	.attach_dmabuf	= vb2_dma_sg_attach_dmabuf,
 	.detach_dmabuf	= vb2_dma_sg_detach_dmabuf,
 	.cookie		= vb2_dma_sg_cookie,
 };
 EXPORT_SYMBOL_GPL(vb2_dma_sg_memops);

 void *vb2_dma_sg_init_ctx(struct device *dev)
 {
 	struct vb2_dma_sg_conf *conf;

 	conf = kzalloc(sizeof(*conf), GFP_KERNEL);
 	if (!conf)
 		return ERR_PTR(-ENOMEM);

 	conf->dev = dev;

 	return conf;
 }
 EXPORT_SYMBOL_GPL(vb2_dma_sg_init_ctx);

 void vb2_dma_sg_cleanup_ctx(void *alloc_ctx)
 {
 	if (!IS_ERR_OR_NULL(alloc_ctx))
 		kfree(alloc_ctx);
 }
 EXPORT_SYMBOL_GPL(vb2_dma_sg_cleanup_ctx);

 MODULE_DESCRIPTION("dma scatter/gather memory handling routines for videobuf2");
 MODULE_AUTHOR("Andrzej Pietrasiewicz");
 MODULE_LICENSE("GPL");
	/*
	* videobuf2-dma-sg.c - dma scatter/gather memory allocator for videobuf2
	*
	* Copyright (C) 2010 Samsung Electronics
	*
	* Author: Andrzej Pietrasiewicz <andrzej.p@samsung.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/module.h>
	#include <linux/mm.h>
	#include <linux/scatterlist.h>
	#include <linux/sched.h>
	#include <linux/slab.h>
	#include <linux/vmalloc.h>

	#include <media/videobuf2-core.h>
	#include <media/videobuf2-memops.h>
	#include <media/videobuf2-dma-sg.h>

	static int debug;
	module_param(debug, int, 0644);

	#define dprintk(level, fmt, arg...) \
	do { \
	if (debug >= level) \
	printk(KERN_DEBUG "vb2-dma-sg: " fmt, ## arg); \
	} while (0)

	struct vb2_dma_sg_conf {
	struct device *dev;
	};

	struct vb2_dma_sg_buf {
	struct device *dev;
	void *vaddr;
	struct page **pages;
	int offset;
	enum dma_data_direction dma_dir;
	struct sg_table sg_table;
	/*
	* This will point to sg_table when used with the MMAP or USERPTR
	* memory model, and to the dma_buf sglist when used with the
	* DMABUF memory model.
	*/
	struct sg_table *dma_sgt;
	size_t size;
	unsigned int num_pages;
	atomic_t refcount;
	struct vb2_vmarea_handler handler;
	struct vm_area_struct *vma;

	struct dma_buf_attachment *db_attach;
	};

	static void vb2_dma_sg_put(void *buf_priv);

	static int vb2_dma_sg_alloc_compacted(struct vb2_dma_sg_buf *buf,
	gfp_t gfp_flags)
	{
	unsigned int last_page = 0;
	int size = buf->size;

	while (size > 0) {
	struct page *pages;
	int order;
	int i;

	order = get_order(size);
	/* Dont over allocate*/
	if ((PAGE_SIZE << order) > size)
	order--;

	pages = NULL;
	while (!pages) {
	pages = alloc_pages(GFP_KERNEL \| __GFP_ZERO \|
	__GFP_NOWARN \| gfp_flags, order);
	if (pages)
	break;

	if (order == 0) {
	while (last_page--)
	__free_page(buf->pages[last_page]);
	return -ENOMEM;
	}
	order--;
	}

	split_page(pages, order);
	for (i = 0; i < (1 << order); i++)
	buf->pages[last_page++] = &pages[i];

	size -= PAGE_SIZE << order;
	}

	return 0;
	}

	static void vb2_dma_sg_alloc(void alloc_ctx, unsigned long size,
	enum dma_data_direction dma_dir, gfp_t gfp_flags)
	{
	struct vb2_dma_sg_conf *conf = alloc_ctx;
	struct vb2_dma_sg_buf *buf;
	struct sg_table *sgt;
	int ret;
	int num_pages;
	DEFINE_DMA_ATTRS(attrs);

	dma_set_attr(DMA_ATTR_SKIP_CPU_SYNC, &attrs);

	if (WARN_ON(alloc_ctx == NULL))
	return NULL;
	buf = kzalloc(sizeof *buf, GFP_KERNEL);
	if (!buf)
	return NULL;

	buf->vaddr = NULL;
	buf->dma_dir = dma_dir;
	buf->offset = 0;
	buf->size = size;
	/* size is already page aligned */
	buf->num_pages = size >> PAGE_SHIFT;
	buf->dma_sgt = &buf->sg_table;

	buf->pages = kzalloc(buf->num_pages * sizeof(struct page *),
	GFP_KERNEL);
	if (!buf->pages)
	goto fail_pages_array_alloc;

	ret = vb2_dma_sg_alloc_compacted(buf, gfp_flags);
	if (ret)
	goto fail_pages_alloc;

	ret = sg_alloc_table_from_pages(buf->dma_sgt, buf->pages,
	buf->num_pages, 0, size, GFP_KERNEL);
	if (ret)
	goto fail_table_alloc;

	/* Prevent the device from being released while the buffer is used */
	buf->dev = get_device(conf->dev);

	sgt = &buf->sg_table;
	/*
	* 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, &attrs);
	if (!sgt->nents)
	goto fail_map;

	buf->handler.refcount = &buf->refcount;
	buf->handler.put = vb2_dma_sg_put;
	buf->handler.arg = buf;

	atomic_inc(&buf->refcount);

	dprintk(1, "%s: Allocated buffer of %d pages\n",
	__func__, buf->num_pages);
	return buf;

	fail_map:
	put_device(buf->dev);
	sg_free_table(buf->dma_sgt);
	fail_table_alloc:
	num_pages = buf->num_pages;
	while (num_pages--)
	__free_page(buf->pages[num_pages]);
	fail_pages_alloc:
	kfree(buf->pages);
	fail_pages_array_alloc:
	kfree(buf);
	return NULL;
	}

	static void vb2_dma_sg_put(void *buf_priv)
	{
	struct vb2_dma_sg_buf *buf = buf_priv;
	struct sg_table *sgt = &buf->sg_table;
	int i = buf->num_pages;

	if (atomic_dec_and_test(&buf->refcount)) {
	DEFINE_DMA_ATTRS(attrs);

	dma_set_attr(DMA_ATTR_SKIP_CPU_SYNC, &attrs);
	dprintk(1, "%s: Freeing buffer of %d pages\n", __func__,
	buf->num_pages);
	dma_unmap_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents,
	buf->dma_dir, &attrs);
	if (buf->vaddr)
	vm_unmap_ram(buf->vaddr, buf->num_pages);
	sg_free_table(buf->dma_sgt);
	while (--i >= 0)
	__free_page(buf->pages[i]);
	kfree(buf->pages);
	put_device(buf->dev);
	kfree(buf);
	}
	}

	static void vb2_dma_sg_prepare(void *buf_priv)
	{
	struct vb2_dma_sg_buf *buf = buf_priv;
	struct sg_table *sgt = buf->dma_sgt;

	/* DMABUF exporter will flush the cache for us */
	if (buf->db_attach)
	return;

	dma_sync_sg_for_device(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);
	}

	static void vb2_dma_sg_finish(void *buf_priv)
	{
	struct vb2_dma_sg_buf *buf = buf_priv;
	struct sg_table *sgt = buf->dma_sgt;

	/* DMABUF exporter will flush the cache for us */
	if (buf->db_attach)
	return;

	dma_sync_sg_for_cpu(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);
	}

	static inline int vma_is_io(struct vm_area_struct *vma)
	{
	return !!(vma->vm_flags & (VM_IO \| VM_PFNMAP));
	}

	static void vb2_dma_sg_get_userptr(void alloc_ctx, unsigned long vaddr,
	unsigned long size,
	enum dma_data_direction dma_dir)
	{
	struct vb2_dma_sg_conf *conf = alloc_ctx;
	struct vb2_dma_sg_buf *buf;
	unsigned long first, last;
	int num_pages_from_user;
	struct vm_area_struct *vma;
	struct sg_table *sgt;
	DEFINE_DMA_ATTRS(attrs);

	dma_set_attr(DMA_ATTR_SKIP_CPU_SYNC, &attrs);

	buf = kzalloc(sizeof *buf, GFP_KERNEL);
	if (!buf)
	return NULL;

	buf->vaddr = NULL;
	buf->dev = conf->dev;
	buf->dma_dir = dma_dir;
	buf->offset = vaddr & ~PAGE_MASK;
	buf->size = size;
	buf->dma_sgt = &buf->sg_table;

	first = (vaddr & PAGE_MASK) >> PAGE_SHIFT;
	last = ((vaddr + size - 1) & PAGE_MASK) >> PAGE_SHIFT;
	buf->num_pages = last - first + 1;

	buf->pages = kzalloc(buf->num_pages * sizeof(struct page *),
	GFP_KERNEL);
	if (!buf->pages)
	goto userptr_fail_alloc_pages;

	vma = find_vma(current->mm, vaddr);
	if (!vma) {
	dprintk(1, "no vma for address %lu\n", vaddr);
	goto userptr_fail_find_vma;
	}

	if (vma->vm_end < vaddr + size) {
	dprintk(1, "vma at %lu is too small for %lu bytes\n",
	vaddr, size);
	goto userptr_fail_find_vma;
	}

	buf->vma = vb2_get_vma(vma);
	if (!buf->vma) {
	dprintk(1, "failed to copy vma\n");
	goto userptr_fail_find_vma;
	}

	if (vma_is_io(buf->vma)) {
	for (num_pages_from_user = 0;
	num_pages_from_user < buf->num_pages;
	++num_pages_from_user, vaddr += PAGE_SIZE) {
	unsigned long pfn;

	if (follow_pfn(vma, vaddr, &pfn)) {
	dprintk(1, "no page for address %lu\n", vaddr);
	break;
	}
	buf->pages[num_pages_from_user] = pfn_to_page(pfn);
	}
	} else
	num_pages_from_user = get_user_pages(current, current->mm,
	vaddr & PAGE_MASK,
	buf->num_pages,
	buf->dma_dir == DMA_FROM_DEVICE,
	1, /* force */
	buf->pages,
	NULL);

	if (num_pages_from_user != buf->num_pages)
	goto userptr_fail_get_user_pages;

	if (sg_alloc_table_from_pages(buf->dma_sgt, buf->pages,
	buf->num_pages, buf->offset, size, 0))
	goto userptr_fail_alloc_table_from_pages;

	sgt = &buf->sg_table;
	/*
	* 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, &attrs);
	if (!sgt->nents)
	goto userptr_fail_map;

	return buf;

	userptr_fail_map:
	sg_free_table(&buf->sg_table);
	userptr_fail_alloc_table_from_pages:
	userptr_fail_get_user_pages:
	dprintk(1, "get_user_pages requested/got: %d/%d]\n",
	buf->num_pages, num_pages_from_user);
	if (!vma_is_io(buf->vma))
	while (--num_pages_from_user >= 0)
	put_page(buf->pages[num_pages_from_user]);
	vb2_put_vma(buf->vma);
	userptr_fail_find_vma:
	kfree(buf->pages);
	userptr_fail_alloc_pages:
	kfree(buf);
	return NULL;
	}

	/*
	* @put_userptr: inform the allocator that a USERPTR buffer will no longer
	* be used
	*/
	static void vb2_dma_sg_put_userptr(void *buf_priv)
	{
	struct vb2_dma_sg_buf *buf = buf_priv;
	struct sg_table *sgt = &buf->sg_table;
	int i = buf->num_pages;
	DEFINE_DMA_ATTRS(attrs);

	dma_set_attr(DMA_ATTR_SKIP_CPU_SYNC, &attrs);

	dprintk(1, "%s: Releasing userspace buffer of %d pages\n",
	__func__, buf->num_pages);
	dma_unmap_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents, buf->dma_dir,
	&attrs);
	if (buf->vaddr)
	vm_unmap_ram(buf->vaddr, buf->num_pages);
	sg_free_table(buf->dma_sgt);
	while (--i >= 0) {
	if (buf->dma_dir == DMA_FROM_DEVICE)
	set_page_dirty_lock(buf->pages[i]);
	if (!vma_is_io(buf->vma))
	put_page(buf->pages[i]);
	}
	kfree(buf->pages);
	vb2_put_vma(buf->vma);
	kfree(buf);
	}

	static void vb2_dma_sg_vaddr(void buf_priv)
	{
	struct vb2_dma_sg_buf *buf = buf_priv;

	BUG_ON(!buf);

	if (!buf->vaddr) {
	if (buf->db_attach)
	buf->vaddr = dma_buf_vmap(buf->db_attach->dmabuf);
	else
	buf->vaddr = vm_map_ram(buf->pages,
	buf->num_pages, -1, PAGE_KERNEL);
	}

	/* add offset in case userptr is not page-aligned */
	return buf->vaddr ? buf->vaddr + buf->offset : NULL;
	}

	static unsigned int vb2_dma_sg_num_users(void *buf_priv)
	{
	struct vb2_dma_sg_buf *buf = buf_priv;

	return atomic_read(&buf->refcount);
	}

	static int vb2_dma_sg_mmap(void buf_priv, struct vm_area_struct vma)
	{
	struct vb2_dma_sg_buf *buf = buf_priv;
	unsigned long uaddr = vma->vm_start;
	unsigned long usize = vma->vm_end - vma->vm_start;
	int i = 0;

	if (!buf) {
	printk(KERN_ERR "No memory to map\n");
	return -EINVAL;
	}

	do {
	int ret;

	ret = vm_insert_page(vma, uaddr, buf->pages[i++]);
	if (ret) {
	printk(KERN_ERR "Remapping memory, error: %d\n", ret);
	return ret;
	}

	uaddr += PAGE_SIZE;
	usize -= PAGE_SIZE;
	} while (usize > 0);


	/*
	* Use common vm_area operations to track buffer refcount.
	*/
	vma->vm_private_data = &buf->handler;
	vma->vm_ops = &vb2_common_vm_ops;

	vma->vm_ops->open(vma);

	return 0;
	}

	/*********************************************/
	/* DMABUF ops for exporters */
	/*********************************************/

	struct vb2_dma_sg_attachment {
	struct sg_table sgt;
	enum dma_data_direction dma_dir;
	};

	static int vb2_dma_sg_dmabuf_ops_attach(struct dma_buf dbuf, struct device dev,
	struct dma_buf_attachment *dbuf_attach)
	{
	struct vb2_dma_sg_attachment *attach;
	unsigned int i;
	struct scatterlist rd, wr;
	struct sg_table *sgt;
	struct vb2_dma_sg_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->dma_sgt->orig_nents, GFP_KERNEL);
	if (ret) {
	kfree(attach);
	return -ENOMEM;
	}

	rd = buf->dma_sgt->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_dma_sg_dmabuf_ops_detach(struct dma_buf *dbuf,
	struct dma_buf_attachment *db_attach)
	{
	struct vb2_dma_sg_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_dma_sg_dmabuf_ops_map(
	struct dma_buf_attachment *db_attach, enum dma_data_direction dma_dir)
	{
	struct vb2_dma_sg_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_dma_sg_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_dma_sg_dmabuf_ops_release(struct dma_buf *dbuf)
	{
	/* drop reference obtained in vb2_dma_sg_get_dmabuf */
	vb2_dma_sg_put(dbuf->priv);
	}

	static void vb2_dma_sg_dmabuf_ops_kmap(struct dma_buf dbuf, unsigned long pgnum)
	{
	struct vb2_dma_sg_buf *buf = dbuf->priv;

	return buf->vaddr ? buf->vaddr + pgnum * PAGE_SIZE : NULL;
	}

	static void vb2_dma_sg_dmabuf_ops_vmap(struct dma_buf dbuf)
	{
	struct vb2_dma_sg_buf *buf = dbuf->priv;

	return vb2_dma_sg_vaddr(buf);
	}

	static int vb2_dma_sg_dmabuf_ops_mmap(struct dma_buf *dbuf,
	struct vm_area_struct *vma)
	{
	return vb2_dma_sg_mmap(dbuf->priv, vma);
	}

	static struct dma_buf_ops vb2_dma_sg_dmabuf_ops = {
	.attach = vb2_dma_sg_dmabuf_ops_attach,
	.detach = vb2_dma_sg_dmabuf_ops_detach,
	.map_dma_buf = vb2_dma_sg_dmabuf_ops_map,
	.unmap_dma_buf = vb2_dma_sg_dmabuf_ops_unmap,
	.kmap = vb2_dma_sg_dmabuf_ops_kmap,
	.kmap_atomic = vb2_dma_sg_dmabuf_ops_kmap,
	.vmap = vb2_dma_sg_dmabuf_ops_vmap,
	.mmap = vb2_dma_sg_dmabuf_ops_mmap,
	.release = vb2_dma_sg_dmabuf_ops_release,
	};

	static struct dma_buf vb2_dma_sg_get_dmabuf(void buf_priv, unsigned long flags)
	{
	struct vb2_dma_sg_buf *buf = buf_priv;
	struct dma_buf *dbuf;
	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);

	exp_info.ops = &vb2_dma_sg_dmabuf_ops;
	exp_info.size = buf->size;
	exp_info.flags = flags;
	exp_info.priv = buf;

	if (WARN_ON(!buf->dma_sgt))
	return NULL;

	dbuf = dma_buf_export(&exp_info);
	if (IS_ERR(dbuf))
	return NULL;

	/* dmabuf keeps reference to vb2 buffer */
	atomic_inc(&buf->refcount);

	return dbuf;
	}

	/*********************************************/
	/* callbacks for DMABUF buffers */
	/*********************************************/

	static int vb2_dma_sg_map_dmabuf(void *mem_priv)
	{
	struct vb2_dma_sg_buf *buf = mem_priv;
	struct sg_table *sgt;

	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;
	}

	buf->dma_sgt = sgt;
	buf->vaddr = NULL;

	return 0;
	}

	static void vb2_dma_sg_unmap_dmabuf(void *mem_priv)
	{
	struct vb2_dma_sg_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_sgt = NULL;
	}

	static void vb2_dma_sg_detach_dmabuf(void *mem_priv)
	{
	struct vb2_dma_sg_buf *buf = mem_priv;

	/* if vb2 works correctly you should never detach mapped buffer */
	if (WARN_ON(buf->dma_sgt))
	vb2_dma_sg_unmap_dmabuf(buf);

	/* detach this attachment */
	dma_buf_detach(buf->db_attach->dmabuf, buf->db_attach);
	kfree(buf);
	}

	static void vb2_dma_sg_attach_dmabuf(void alloc_ctx, struct dma_buf *dbuf,
	unsigned long size, enum dma_data_direction dma_dir)
	{
	struct vb2_dma_sg_conf *conf = alloc_ctx;
	struct vb2_dma_sg_buf *buf;
	struct dma_buf_attachment *dba;

	if (dbuf->size < size)
	return ERR_PTR(-EFAULT);

	buf = kzalloc(sizeof(*buf), GFP_KERNEL);
	if (!buf)
	return ERR_PTR(-ENOMEM);

	buf->dev = conf->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;
	}

	static void vb2_dma_sg_cookie(void buf_priv)
	{
	struct vb2_dma_sg_buf *buf = buf_priv;

	return buf->dma_sgt;
	}

	const struct vb2_mem_ops vb2_dma_sg_memops = {
	.alloc = vb2_dma_sg_alloc,
	.put = vb2_dma_sg_put,
	.get_userptr = vb2_dma_sg_get_userptr,
	.put_userptr = vb2_dma_sg_put_userptr,
	.prepare = vb2_dma_sg_prepare,
	.finish = vb2_dma_sg_finish,
	.vaddr = vb2_dma_sg_vaddr,
	.mmap = vb2_dma_sg_mmap,
	.num_users = vb2_dma_sg_num_users,
	.get_dmabuf = vb2_dma_sg_get_dmabuf,
	.map_dmabuf = vb2_dma_sg_map_dmabuf,
	.unmap_dmabuf = vb2_dma_sg_unmap_dmabuf,
	.attach_dmabuf = vb2_dma_sg_attach_dmabuf,
	.detach_dmabuf = vb2_dma_sg_detach_dmabuf,
	.cookie = vb2_dma_sg_cookie,
	};
	EXPORT_SYMBOL_GPL(vb2_dma_sg_memops);

	void vb2_dma_sg_init_ctx(struct device dev)
	{
	struct vb2_dma_sg_conf *conf;

	conf = kzalloc(sizeof(*conf), GFP_KERNEL);
	if (!conf)
	return ERR_PTR(-ENOMEM);

	conf->dev = dev;

	return conf;
	}
	EXPORT_SYMBOL_GPL(vb2_dma_sg_init_ctx);

	void vb2_dma_sg_cleanup_ctx(void *alloc_ctx)
	{
	if (!IS_ERR_OR_NULL(alloc_ctx))
	kfree(alloc_ctx);
	}
	EXPORT_SYMBOL_GPL(vb2_dma_sg_cleanup_ctx);

	MODULE_DESCRIPTION("dma scatter/gather memory handling routines for videobuf2");
	MODULE_AUTHOR("Andrzej Pietrasiewicz");
	MODULE_LICENSE("GPL");