drivers/media/v4l2-core/videobuf2-vmalloc.c - kernel/msm-4.9 - Gitiles

 /*
  * videobuf2-vmalloc.c - vmalloc 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/io.h>
 #include <linux/module.h>
 #include <linux/mm.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/vmalloc.h>

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

 struct vb2_vmalloc_buf {
 	void				*vaddr;
 	struct page			**pages;
 	struct vm_area_struct		*vma;
 	enum dma_data_direction		dma_dir;
 	unsigned long			size;
 	unsigned int			n_pages;
 	atomic_t			refcount;
 	struct vb2_vmarea_handler	handler;
 	struct dma_buf			*dbuf;
 };

 static void vb2_vmalloc_put(void *buf_priv);

 static void *vb2_vmalloc_alloc(void *alloc_ctx, unsigned long size,
 			       enum dma_data_direction dma_dir, gfp_t gfp_flags)
 {
 	struct vb2_vmalloc_buf *buf;

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

 	buf->size = size;
 	buf->vaddr = vmalloc_user(buf->size);
 	buf->dma_dir = dma_dir;
 	buf->handler.refcount = &buf->refcount;
 	buf->handler.put = vb2_vmalloc_put;
 	buf->handler.arg = buf;

 	if (!buf->vaddr) {
 		pr_debug("vmalloc of size %ld failed\n", buf->size);
 		kfree(buf);
 		return NULL;
 	}

 	atomic_inc(&buf->refcount);
 	return buf;
 }

 static void vb2_vmalloc_put(void *buf_priv)
 {
 	struct vb2_vmalloc_buf *buf = buf_priv;

 	if (atomic_dec_and_test(&buf->refcount)) {
 		vfree(buf->vaddr);
 		kfree(buf);
 	}
 }

 static void *vb2_vmalloc_get_userptr(void *alloc_ctx, unsigned long vaddr,
 				     unsigned long size,
 				     enum dma_data_direction dma_dir)
 {
 	struct vb2_vmalloc_buf *buf;
 	unsigned long first, last;
 	int n_pages, offset;
 	struct vm_area_struct *vma;
 	dma_addr_t physp;

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

 	buf->dma_dir = dma_dir;
 	offset = vaddr & ~PAGE_MASK;
 	buf->size = size;


 	vma = find_vma(current->mm, vaddr);
 	if (vma && (vma->vm_flags & VM_PFNMAP) && (vma->vm_pgoff)) {
 		if (vb2_get_contig_userptr(vaddr, size, &vma, &physp))
 			goto fail_pages_array_alloc;
 		buf->vma = vma;
 		buf->vaddr = (__force void *)ioremap_nocache(physp, size);
 		if (!buf->vaddr)
 			goto fail_pages_array_alloc;
 	} else {
 		first = vaddr >> PAGE_SHIFT;
 		last  = (vaddr + size - 1) >> PAGE_SHIFT;
 		buf->n_pages = last - first + 1;
 		buf->pages = kzalloc(buf->n_pages * sizeof(struct page *),
 				     GFP_KERNEL);
 		if (!buf->pages)
 			goto fail_pages_array_alloc;

 		/* current->mm->mmap_sem is taken by videobuf2 core */
 		n_pages = get_user_pages(current, current->mm,
 					 vaddr & PAGE_MASK, buf->n_pages,
 					 dma_dir == DMA_FROM_DEVICE,
 					 1, /* force */
 					 buf->pages, NULL);
 		if (n_pages != buf->n_pages)
 			goto fail_get_user_pages;

 		buf->vaddr = vm_map_ram(buf->pages, buf->n_pages, -1,
 					PAGE_KERNEL);
 		if (!buf->vaddr)
 			goto fail_get_user_pages;
 	}

 	buf->vaddr += offset;
 	return buf;

 fail_get_user_pages:
 	pr_debug("get_user_pages requested/got: %d/%d]\n", n_pages,
 		 buf->n_pages);
 	while (--n_pages >= 0)
 		put_page(buf->pages[n_pages]);
 	kfree(buf->pages);

 fail_pages_array_alloc:
 	kfree(buf);

 	return NULL;
 }

 static void vb2_vmalloc_put_userptr(void *buf_priv)
 {
 	struct vb2_vmalloc_buf *buf = buf_priv;
 	unsigned long vaddr = (unsigned long)buf->vaddr & PAGE_MASK;
 	unsigned int i;

 	if (buf->pages) {
 		if (vaddr)
 			vm_unmap_ram((void *)vaddr, buf->n_pages);
 		for (i = 0; i < buf->n_pages; ++i) {
 			if (buf->dma_dir == DMA_FROM_DEVICE)
 				set_page_dirty_lock(buf->pages[i]);
 			put_page(buf->pages[i]);
 		}
 		kfree(buf->pages);
 	} else {
 		vb2_put_vma(buf->vma);
 		iounmap((__force void __iomem *)buf->vaddr);
 	}
 	kfree(buf);
 }

 static void *vb2_vmalloc_vaddr(void *buf_priv)
 {
 	struct vb2_vmalloc_buf *buf = buf_priv;

 	if (!buf->vaddr) {
 		pr_err("Address of an unallocated plane requested "
 		       "or cannot map user pointer\n");
 		return NULL;
 	}

 	return buf->vaddr;
 }

 static unsigned int vb2_vmalloc_num_users(void *buf_priv)
 {
 	struct vb2_vmalloc_buf *buf = buf_priv;
 	return atomic_read(&buf->refcount);
 }

 static int vb2_vmalloc_mmap(void *buf_priv, struct vm_area_struct *vma)
 {
 	struct vb2_vmalloc_buf *buf = buf_priv;
 	int ret;

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

 	ret = remap_vmalloc_range(vma, buf->vaddr, 0);
 	if (ret) {
 		pr_err("Remapping vmalloc memory, error: %d\n", ret);
 		return ret;
 	}

 	/*
 	 * Make sure that vm_areas for 2 buffers won't be merged together
 	 */
 	vma->vm_flags		|= VM_DONTEXPAND;

 	/*
 	 * 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;
 }

 #ifdef CONFIG_HAS_DMA
 /*********************************************/
 /*         DMABUF ops for exporters          */
 /*********************************************/

 struct vb2_vmalloc_attachment {
 	struct sg_table sgt;
 	enum dma_data_direction dma_dir;
 };

 static int vb2_vmalloc_dmabuf_ops_attach(struct dma_buf *dbuf, struct device *dev,
 	struct dma_buf_attachment *dbuf_attach)
 {
 	struct vb2_vmalloc_attachment *attach;
 	struct vb2_vmalloc_buf *buf = dbuf->priv;
 	int num_pages = PAGE_ALIGN(buf->size) / PAGE_SIZE;
 	struct sg_table *sgt;
 	struct scatterlist *sg;
 	void *vaddr = buf->vaddr;
 	int ret;
 	int i;

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

 	sgt = &attach->sgt;
 	ret = sg_alloc_table(sgt, num_pages, GFP_KERNEL);
 	if (ret) {
 		kfree(attach);
 		return ret;
 	}
 	for_each_sg(sgt->sgl, sg, sgt->nents, i) {
 		struct page *page = vmalloc_to_page(vaddr);

 		if (!page) {
 			sg_free_table(sgt);
 			kfree(attach);
 			return -ENOMEM;
 		}
 		sg_set_page(sg, page, PAGE_SIZE, 0);
 		vaddr += PAGE_SIZE;
 	}

 	attach->dma_dir = DMA_NONE;
 	dbuf_attach->priv = attach;
 	return 0;
 }

 static void vb2_vmalloc_dmabuf_ops_detach(struct dma_buf *dbuf,
 	struct dma_buf_attachment *db_attach)
 {
 	struct vb2_vmalloc_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_vmalloc_dmabuf_ops_map(
 	struct dma_buf_attachment *db_attach, enum dma_data_direction dma_dir)
 {
 	struct vb2_vmalloc_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_vmalloc_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_vmalloc_dmabuf_ops_release(struct dma_buf *dbuf)
 {
 	/* drop reference obtained in vb2_vmalloc_get_dmabuf */
 	vb2_vmalloc_put(dbuf->priv);
 }

 static void *vb2_vmalloc_dmabuf_ops_kmap(struct dma_buf *dbuf, unsigned long pgnum)
 {
 	struct vb2_vmalloc_buf *buf = dbuf->priv;

 	return buf->vaddr + pgnum * PAGE_SIZE;
 }

 static void *vb2_vmalloc_dmabuf_ops_vmap(struct dma_buf *dbuf)
 {
 	struct vb2_vmalloc_buf *buf = dbuf->priv;

 	return buf->vaddr;
 }

 static int vb2_vmalloc_dmabuf_ops_mmap(struct dma_buf *dbuf,
 	struct vm_area_struct *vma)
 {
 	return vb2_vmalloc_mmap(dbuf->priv, vma);
 }

 static struct dma_buf_ops vb2_vmalloc_dmabuf_ops = {
 	.attach = vb2_vmalloc_dmabuf_ops_attach,
 	.detach = vb2_vmalloc_dmabuf_ops_detach,
 	.map_dma_buf = vb2_vmalloc_dmabuf_ops_map,
 	.unmap_dma_buf = vb2_vmalloc_dmabuf_ops_unmap,
 	.kmap = vb2_vmalloc_dmabuf_ops_kmap,
 	.kmap_atomic = vb2_vmalloc_dmabuf_ops_kmap,
 	.vmap = vb2_vmalloc_dmabuf_ops_vmap,
 	.mmap = vb2_vmalloc_dmabuf_ops_mmap,
 	.release = vb2_vmalloc_dmabuf_ops_release,
 };

 static struct dma_buf *vb2_vmalloc_get_dmabuf(void *buf_priv, unsigned long flags)
 {
 	struct vb2_vmalloc_buf *buf = buf_priv;
 	struct dma_buf *dbuf;
 	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);

 	exp_info.ops = &vb2_vmalloc_dmabuf_ops;
 	exp_info.size = buf->size;
 	exp_info.flags = flags;
 	exp_info.priv = buf;

 	if (WARN_ON(!buf->vaddr))
 		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;
 }
 #endif /* CONFIG_HAS_DMA */


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

 static int vb2_vmalloc_map_dmabuf(void *mem_priv)
 {
 	struct vb2_vmalloc_buf *buf = mem_priv;

 	buf->vaddr = dma_buf_vmap(buf->dbuf);

 	return buf->vaddr ? 0 : -EFAULT;
 }

 static void vb2_vmalloc_unmap_dmabuf(void *mem_priv)
 {
 	struct vb2_vmalloc_buf *buf = mem_priv;

 	dma_buf_vunmap(buf->dbuf, buf->vaddr);
 	buf->vaddr = NULL;
 }

 static void vb2_vmalloc_detach_dmabuf(void *mem_priv)
 {
 	struct vb2_vmalloc_buf *buf = mem_priv;

 	if (buf->vaddr)
 		dma_buf_vunmap(buf->dbuf, buf->vaddr);

 	kfree(buf);
 }

 static void *vb2_vmalloc_attach_dmabuf(void *alloc_ctx, struct dma_buf *dbuf,
 	unsigned long size, enum dma_data_direction dma_dir)
 {
 	struct vb2_vmalloc_buf *buf;

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

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

 	buf->dbuf = dbuf;
 	buf->dma_dir = dma_dir;
 	buf->size = size;

 	return buf;
 }


 const struct vb2_mem_ops vb2_vmalloc_memops = {
 	.alloc		= vb2_vmalloc_alloc,
 	.put		= vb2_vmalloc_put,
 	.get_userptr	= vb2_vmalloc_get_userptr,
 	.put_userptr	= vb2_vmalloc_put_userptr,
 #ifdef CONFIG_HAS_DMA
 	.get_dmabuf	= vb2_vmalloc_get_dmabuf,
 #endif
 	.map_dmabuf	= vb2_vmalloc_map_dmabuf,
 	.unmap_dmabuf	= vb2_vmalloc_unmap_dmabuf,
 	.attach_dmabuf	= vb2_vmalloc_attach_dmabuf,
 	.detach_dmabuf	= vb2_vmalloc_detach_dmabuf,
 	.vaddr		= vb2_vmalloc_vaddr,
 	.mmap		= vb2_vmalloc_mmap,
 	.num_users	= vb2_vmalloc_num_users,
 };
 EXPORT_SYMBOL_GPL(vb2_vmalloc_memops);

 MODULE_DESCRIPTION("vmalloc memory handling routines for videobuf2");
 MODULE_AUTHOR("Pawel Osciak <pawel@osciak.com>");
 MODULE_LICENSE("GPL");
	/*
	* videobuf2-vmalloc.c - vmalloc 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/io.h>
	#include <linux/module.h>
	#include <linux/mm.h>
	#include <linux/sched.h>
	#include <linux/slab.h>
	#include <linux/vmalloc.h>

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

	struct vb2_vmalloc_buf {
	void *vaddr;
	struct page **pages;
	struct vm_area_struct *vma;
	enum dma_data_direction dma_dir;
	unsigned long size;
	unsigned int n_pages;
	atomic_t refcount;
	struct vb2_vmarea_handler handler;
	struct dma_buf *dbuf;
	};

	static void vb2_vmalloc_put(void *buf_priv);

	static void vb2_vmalloc_alloc(void alloc_ctx, unsigned long size,
	enum dma_data_direction dma_dir, gfp_t gfp_flags)
	{
	struct vb2_vmalloc_buf *buf;

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

	buf->size = size;
	buf->vaddr = vmalloc_user(buf->size);
	buf->dma_dir = dma_dir;
	buf->handler.refcount = &buf->refcount;
	buf->handler.put = vb2_vmalloc_put;
	buf->handler.arg = buf;

	if (!buf->vaddr) {
	pr_debug("vmalloc of size %ld failed\n", buf->size);
	kfree(buf);
	return NULL;
	}

	atomic_inc(&buf->refcount);
	return buf;
	}

	static void vb2_vmalloc_put(void *buf_priv)
	{
	struct vb2_vmalloc_buf *buf = buf_priv;

	if (atomic_dec_and_test(&buf->refcount)) {
	vfree(buf->vaddr);
	kfree(buf);
	}
	}

	static void vb2_vmalloc_get_userptr(void alloc_ctx, unsigned long vaddr,
	unsigned long size,
	enum dma_data_direction dma_dir)
	{
	struct vb2_vmalloc_buf *buf;
	unsigned long first, last;
	int n_pages, offset;
	struct vm_area_struct *vma;
	dma_addr_t physp;

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

	buf->dma_dir = dma_dir;
	offset = vaddr & ~PAGE_MASK;
	buf->size = size;


	vma = find_vma(current->mm, vaddr);
	if (vma && (vma->vm_flags & VM_PFNMAP) && (vma->vm_pgoff)) {
	if (vb2_get_contig_userptr(vaddr, size, &vma, &physp))
	goto fail_pages_array_alloc;
	buf->vma = vma;
	buf->vaddr = (__force void *)ioremap_nocache(physp, size);
	if (!buf->vaddr)
	goto fail_pages_array_alloc;
	} else {
	first = vaddr >> PAGE_SHIFT;
	last = (vaddr + size - 1) >> PAGE_SHIFT;
	buf->n_pages = last - first + 1;
	buf->pages = kzalloc(buf->n_pages * sizeof(struct page *),
	GFP_KERNEL);
	if (!buf->pages)
	goto fail_pages_array_alloc;

	/* current->mm->mmap_sem is taken by videobuf2 core */
	n_pages = get_user_pages(current, current->mm,
	vaddr & PAGE_MASK, buf->n_pages,
	dma_dir == DMA_FROM_DEVICE,
	1, /* force */
	buf->pages, NULL);
	if (n_pages != buf->n_pages)
	goto fail_get_user_pages;

	buf->vaddr = vm_map_ram(buf->pages, buf->n_pages, -1,
	PAGE_KERNEL);
	if (!buf->vaddr)
	goto fail_get_user_pages;
	}

	buf->vaddr += offset;
	return buf;

	fail_get_user_pages:
	pr_debug("get_user_pages requested/got: %d/%d]\n", n_pages,
	buf->n_pages);
	while (--n_pages >= 0)
	put_page(buf->pages[n_pages]);
	kfree(buf->pages);

	fail_pages_array_alloc:
	kfree(buf);

	return NULL;
	}

	static void vb2_vmalloc_put_userptr(void *buf_priv)
	{
	struct vb2_vmalloc_buf *buf = buf_priv;
	unsigned long vaddr = (unsigned long)buf->vaddr & PAGE_MASK;
	unsigned int i;

	if (buf->pages) {
	if (vaddr)
	vm_unmap_ram((void *)vaddr, buf->n_pages);
	for (i = 0; i < buf->n_pages; ++i) {
	if (buf->dma_dir == DMA_FROM_DEVICE)
	set_page_dirty_lock(buf->pages[i]);
	put_page(buf->pages[i]);
	}
	kfree(buf->pages);
	} else {
	vb2_put_vma(buf->vma);
	iounmap((__force void __iomem *)buf->vaddr);
	}
	kfree(buf);
	}

	static void vb2_vmalloc_vaddr(void buf_priv)
	{
	struct vb2_vmalloc_buf *buf = buf_priv;

	if (!buf->vaddr) {
	pr_err("Address of an unallocated plane requested "
	"or cannot map user pointer\n");
	return NULL;
	}

	return buf->vaddr;
	}

	static unsigned int vb2_vmalloc_num_users(void *buf_priv)
	{
	struct vb2_vmalloc_buf *buf = buf_priv;
	return atomic_read(&buf->refcount);
	}

	static int vb2_vmalloc_mmap(void buf_priv, struct vm_area_struct vma)
	{
	struct vb2_vmalloc_buf *buf = buf_priv;
	int ret;

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

	ret = remap_vmalloc_range(vma, buf->vaddr, 0);
	if (ret) {
	pr_err("Remapping vmalloc memory, error: %d\n", ret);
	return ret;
	}

	/*
	* Make sure that vm_areas for 2 buffers won't be merged together
	*/
	vma->vm_flags \|= VM_DONTEXPAND;

	/*
	* 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;
	}

	#ifdef CONFIG_HAS_DMA
	/*********************************************/
	/* DMABUF ops for exporters */
	/*********************************************/

	struct vb2_vmalloc_attachment {
	struct sg_table sgt;
	enum dma_data_direction dma_dir;
	};

	static int vb2_vmalloc_dmabuf_ops_attach(struct dma_buf dbuf, struct device dev,
	struct dma_buf_attachment *dbuf_attach)
	{
	struct vb2_vmalloc_attachment *attach;
	struct vb2_vmalloc_buf *buf = dbuf->priv;
	int num_pages = PAGE_ALIGN(buf->size) / PAGE_SIZE;
	struct sg_table *sgt;
	struct scatterlist *sg;
	void *vaddr = buf->vaddr;
	int ret;
	int i;

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

	sgt = &attach->sgt;
	ret = sg_alloc_table(sgt, num_pages, GFP_KERNEL);
	if (ret) {
	kfree(attach);
	return ret;
	}
	for_each_sg(sgt->sgl, sg, sgt->nents, i) {
	struct page *page = vmalloc_to_page(vaddr);

	if (!page) {
	sg_free_table(sgt);
	kfree(attach);
	return -ENOMEM;
	}
	sg_set_page(sg, page, PAGE_SIZE, 0);
	vaddr += PAGE_SIZE;
	}

	attach->dma_dir = DMA_NONE;
	dbuf_attach->priv = attach;
	return 0;
	}

	static void vb2_vmalloc_dmabuf_ops_detach(struct dma_buf *dbuf,
	struct dma_buf_attachment *db_attach)
	{
	struct vb2_vmalloc_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_vmalloc_dmabuf_ops_map(
	struct dma_buf_attachment *db_attach, enum dma_data_direction dma_dir)
	{
	struct vb2_vmalloc_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_vmalloc_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_vmalloc_dmabuf_ops_release(struct dma_buf *dbuf)
	{
	/* drop reference obtained in vb2_vmalloc_get_dmabuf */
	vb2_vmalloc_put(dbuf->priv);
	}

	static void vb2_vmalloc_dmabuf_ops_kmap(struct dma_buf dbuf, unsigned long pgnum)
	{
	struct vb2_vmalloc_buf *buf = dbuf->priv;

	return buf->vaddr + pgnum * PAGE_SIZE;
	}

	static void vb2_vmalloc_dmabuf_ops_vmap(struct dma_buf dbuf)
	{
	struct vb2_vmalloc_buf *buf = dbuf->priv;

	return buf->vaddr;
	}

	static int vb2_vmalloc_dmabuf_ops_mmap(struct dma_buf *dbuf,
	struct vm_area_struct *vma)
	{
	return vb2_vmalloc_mmap(dbuf->priv, vma);
	}

	static struct dma_buf_ops vb2_vmalloc_dmabuf_ops = {
	.attach = vb2_vmalloc_dmabuf_ops_attach,
	.detach = vb2_vmalloc_dmabuf_ops_detach,
	.map_dma_buf = vb2_vmalloc_dmabuf_ops_map,
	.unmap_dma_buf = vb2_vmalloc_dmabuf_ops_unmap,
	.kmap = vb2_vmalloc_dmabuf_ops_kmap,
	.kmap_atomic = vb2_vmalloc_dmabuf_ops_kmap,
	.vmap = vb2_vmalloc_dmabuf_ops_vmap,
	.mmap = vb2_vmalloc_dmabuf_ops_mmap,
	.release = vb2_vmalloc_dmabuf_ops_release,
	};

	static struct dma_buf vb2_vmalloc_get_dmabuf(void buf_priv, unsigned long flags)
	{
	struct vb2_vmalloc_buf *buf = buf_priv;
	struct dma_buf *dbuf;
	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);

	exp_info.ops = &vb2_vmalloc_dmabuf_ops;
	exp_info.size = buf->size;
	exp_info.flags = flags;
	exp_info.priv = buf;

	if (WARN_ON(!buf->vaddr))
	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;
	}
	#endif /* CONFIG_HAS_DMA */


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

	static int vb2_vmalloc_map_dmabuf(void *mem_priv)
	{
	struct vb2_vmalloc_buf *buf = mem_priv;

	buf->vaddr = dma_buf_vmap(buf->dbuf);

	return buf->vaddr ? 0 : -EFAULT;
	}

	static void vb2_vmalloc_unmap_dmabuf(void *mem_priv)
	{
	struct vb2_vmalloc_buf *buf = mem_priv;

	dma_buf_vunmap(buf->dbuf, buf->vaddr);
	buf->vaddr = NULL;
	}

	static void vb2_vmalloc_detach_dmabuf(void *mem_priv)
	{
	struct vb2_vmalloc_buf *buf = mem_priv;

	if (buf->vaddr)
	dma_buf_vunmap(buf->dbuf, buf->vaddr);

	kfree(buf);
	}

	static void vb2_vmalloc_attach_dmabuf(void alloc_ctx, struct dma_buf *dbuf,
	unsigned long size, enum dma_data_direction dma_dir)
	{
	struct vb2_vmalloc_buf *buf;

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

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

	buf->dbuf = dbuf;
	buf->dma_dir = dma_dir;
	buf->size = size;

	return buf;
	}


	const struct vb2_mem_ops vb2_vmalloc_memops = {
	.alloc = vb2_vmalloc_alloc,
	.put = vb2_vmalloc_put,
	.get_userptr = vb2_vmalloc_get_userptr,
	.put_userptr = vb2_vmalloc_put_userptr,
	#ifdef CONFIG_HAS_DMA
	.get_dmabuf = vb2_vmalloc_get_dmabuf,
	#endif
	.map_dmabuf = vb2_vmalloc_map_dmabuf,
	.unmap_dmabuf = vb2_vmalloc_unmap_dmabuf,
	.attach_dmabuf = vb2_vmalloc_attach_dmabuf,
	.detach_dmabuf = vb2_vmalloc_detach_dmabuf,
	.vaddr = vb2_vmalloc_vaddr,
	.mmap = vb2_vmalloc_mmap,
	.num_users = vb2_vmalloc_num_users,
	};
	EXPORT_SYMBOL_GPL(vb2_vmalloc_memops);

	MODULE_DESCRIPTION("vmalloc memory handling routines for videobuf2");
	MODULE_AUTHOR("Pawel Osciak <pawel@osciak.com>");
	MODULE_LICENSE("GPL");