1 files changed, 645 insertions, 55 deletions

diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c b/drivers/media/v4l2-core/videobuf2-dma-contig.c
index 4b7132660a93..10beaee7f0ae 100644
--- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
+++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
@@ -10,7 +10,10 @@
  * the Free Software Foundation.
  */
 
+#include <linux/dma-buf.h>
 #include <linux/module.h>
+#include <linux/scatterlist.h>
+#include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/dma-mapping.h>
 
@@ -23,40 +26,158 @@ struct vb2_dc_conf {
 };
 
 struct vb2_dc_buf {
-        struct vb2_dc_conf              *conf;
+        struct device                   *dev;
         void                            *vaddr;
-        dma_addr_t                      dma_addr;
         unsigned long                   size;
-        struct vm_area_struct           *vma;
-        atomic_t                        refcount;
+        dma_addr_t                      dma_addr;
+        enum dma_data_direction         dma_dir;
+        struct sg_table                 *dma_sgt;
+
+        /* MMAP related */
         struct vb2_vmarea_handler       handler;
+        atomic_t                        refcount;
+        struct sg_table                 *sgt_base;
+
+        /* USERPTR related */
+        struct vm_area_struct           *vma;
+
+        /* DMABUF related */
+        struct dma_buf_attachment       *db_attach;
 };
 
-static void vb2_dma_contig_put(void *buf_priv);
+/*********************************************/
+/*        scatterlist table functions        */
+/*********************************************/
+
+
+static void vb2_dc_sgt_foreach_page(struct sg_table *sgt,
+        void (*cb)(struct page *pg))
+{
+        struct scatterlist *s;
+        unsigned int i;
+
+        for_each_sg(sgt->sgl, s, sgt->orig_nents, i) {
+                struct page *page = sg_page(s);
+                unsigned int n_pages = PAGE_ALIGN(s->offset + s->length)
+                        >> PAGE_SHIFT;
+                unsigned int j;
+
+                for (j = 0; j < n_pages; ++j, ++page)
+                        cb(page);
+        }
+}
+
+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;
+
+        return buf->vaddr;
+}
+
+static unsigned int vb2_dc_num_users(void *buf_priv)
+{
+        struct vb2_dc_buf *buf = buf_priv;
+
+        return atomic_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->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->nents, buf->dma_dir);
+}
+
+/*********************************************/
+/*        callbacks for MMAP buffers         */
+/*********************************************/
+
+static void vb2_dc_put(void *buf_priv)
+{
+        struct vb2_dc_buf *buf = buf_priv;
+
+        if (!atomic_dec_and_test(&buf->refcount))
+                return;
+
+        if (buf->sgt_base) {
+                sg_free_table(buf->sgt_base);
+                kfree(buf->sgt_base);
+        }
+        dma_free_coherent(buf->dev, buf->size, buf->vaddr, buf->dma_addr);
+        put_device(buf->dev);
+        kfree(buf);
+}
 
-static void *vb2_dma_contig_alloc(void *alloc_ctx, unsigned long size)
+static void *vb2_dc_alloc(void *alloc_ctx, unsigned long size)
 {
         struct vb2_dc_conf *conf = alloc_ctx;
+        struct device *dev = conf->dev;
         struct vb2_dc_buf *buf;
 
         buf = kzalloc(sizeof *buf, GFP_KERNEL);
         if (!buf)
                 return ERR_PTR(-ENOMEM);
 
-        buf->vaddr = dma_alloc_coherent(conf->dev, size, &buf->dma_addr,
-                                        GFP_KERNEL);
+        /* align image size to PAGE_SIZE */
+        size = PAGE_ALIGN(size);
+
+        buf->vaddr = dma_alloc_coherent(dev, size, &buf->dma_addr, GFP_KERNEL);
         if (!buf->vaddr) {
-                dev_err(conf->dev, "dma_alloc_coherent of size %ld failed\n",
-                        size);
+                dev_err(dev, "dma_alloc_coherent of size %ld failed\n", size);
                 kfree(buf);
                 return ERR_PTR(-ENOMEM);
         }
 
-        buf->conf = conf;
+        /* Prevent the device from being released while the buffer is used */
+        buf->dev = get_device(dev);
         buf->size = size;
 
         buf->handler.refcount = &buf->refcount;
-        buf->handler.put = vb2_dma_contig_put;
+        buf->handler.put = vb2_dc_put;
         buf->handler.arg = buf;
 
         atomic_inc(&buf->refcount);
@@ -64,100 +185,569 @@ static void *vb2_dma_contig_alloc(void *alloc_ctx, unsigned long size)
         return buf;
 }
 
-static void vb2_dma_contig_put(void *buf_priv)
+static int vb2_dc_mmap(void *buf_priv, struct vm_area_struct *vma)
 {
         struct vb2_dc_buf *buf = buf_priv;
+        int ret;
 
-        if (atomic_dec_and_test(&buf->refcount)) {
-                dma_free_coherent(buf->conf->dev, buf->size, buf->vaddr,
-                                  buf->dma_addr);
-                kfree(buf);
+        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_coherent(buf->dev, vma, buf->vaddr,
+                buf->dma_addr, buf->size);
+
+        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;
 }
 
-static void *vb2_dma_contig_cookie(void *buf_priv)
+/*********************************************/
+/*         DMABUF ops for exporters          */
+/*********************************************/
+
+struct vb2_dc_attachment {
+        struct sg_table sgt;
+        enum dma_data_direction dir;
+};
+
+static int vb2_dc_dmabuf_ops_attach(struct dma_buf *dbuf, struct device *dev,
+        struct dma_buf_attachment *dbuf_attach)
 {
-        struct vb2_dc_buf *buf = buf_priv;
+        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;
 
-        return &buf->dma_addr;
+        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->dir = DMA_NONE;
+        dbuf_attach->priv = attach;
+
+        return 0;
 }
 
-static void *vb2_dma_contig_vaddr(void *buf_priv)
+static void vb2_dc_dmabuf_ops_detach(struct dma_buf *dbuf,
+        struct dma_buf_attachment *db_attach)
 {
-        struct vb2_dc_buf *buf = buf_priv;
-        if (!buf)
-                return NULL;
+        struct vb2_dc_attachment *attach = db_attach->priv;
+        struct sg_table *sgt;
+
+        if (!attach)
+                return;
+
+        sgt = &attach->sgt;
+
+        /* release the scatterlist cache */
+        if (attach->dir != DMA_NONE)
+                dma_unmap_sg(db_attach->dev, sgt->sgl, sgt->orig_nents,
+                        attach->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 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;
+        int ret;
+
+        mutex_lock(lock);
+
+        sgt = &attach->sgt;
+        /* return previously mapped sg table */
+        if (attach->dir == dir) {
+                mutex_unlock(lock);
+                return sgt;
+        }
+
+        /* release any previous cache */
+        if (attach->dir != DMA_NONE) {
+                dma_unmap_sg(db_attach->dev, sgt->sgl, sgt->orig_nents,
+                        attach->dir);
+                attach->dir = DMA_NONE;
+        }
+
+        /* mapping to the client with new direction */
+        ret = dma_map_sg(db_attach->dev, sgt->sgl, sgt->orig_nents, dir);
+        if (ret <= 0) {
+                pr_err("failed to map scatterlist\n");
+                mutex_unlock(lock);
+                return ERR_PTR(-EIO);
+        }
+
+        attach->dir = 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 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 + pgnum * PAGE_SIZE;
+}
+
+static void *vb2_dc_dmabuf_ops_vmap(struct dma_buf *dbuf)
+{
+        struct vb2_dc_buf *buf = dbuf->priv;
 
         return buf->vaddr;
 }
 
-static unsigned int vb2_dma_contig_num_users(void *buf_priv)
+static int vb2_dc_dmabuf_ops_mmap(struct dma_buf *dbuf,
+        struct vm_area_struct *vma)
 {
-        struct vb2_dc_buf *buf = buf_priv;
+        return vb2_dc_mmap(dbuf->priv, vma);
+}
 
-        return atomic_read(&buf->refcount);
+static 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,
+        .kmap = vb2_dc_dmabuf_ops_kmap,
+        .kmap_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(buf->dev, sgt, buf->vaddr, buf->dma_addr,
+                buf->size);
+        if (ret < 0) {
+                dev_err(buf->dev, "failed to get scatterlist from DMA API\n");
+                kfree(sgt);
+                return NULL;
+        }
+
+        return sgt;
 }
 
-static int vb2_dma_contig_mmap(void *buf_priv, struct vm_area_struct *vma)
+static struct dma_buf *vb2_dc_get_dmabuf(void *buf_priv)
 {
         struct vb2_dc_buf *buf = buf_priv;
+        struct dma_buf *dbuf;
 
-        if (!buf) {
-                printk(KERN_ERR "No buffer to map\n");
-                return -EINVAL;
+        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(buf, &vb2_dc_dmabuf_ops, buf->size, 0);
+        if (IS_ERR(dbuf))
+                return NULL;
+
+        /* dmabuf keeps reference to vb2 buffer */
+        atomic_inc(&buf->refcount);
+
+        return dbuf;
+}
+
+/*********************************************/
+/*       callbacks for USERPTR buffers       */
+/*********************************************/
+
+static inline int vma_is_io(struct vm_area_struct *vma)
+{
+        return !!(vma->vm_flags & (VM_IO | VM_PFNMAP));
+}
+
+static int vb2_dc_get_user_pages(unsigned long start, struct page **pages,
+        int n_pages, struct vm_area_struct *vma, int write)
+{
+        if (vma_is_io(vma)) {
+                unsigned int i;
+
+                for (i = 0; i < n_pages; ++i, start += PAGE_SIZE) {
+                        unsigned long pfn;
+                        int ret = follow_pfn(vma, start, &pfn);
+
+                        if (ret) {
+                                pr_err("no page for address %lu\n", start);
+                                return ret;
+                        }
+                        pages[i] = pfn_to_page(pfn);
+                }
+        } else {
+                int n;
+
+                n = get_user_pages(current, current->mm, start & PAGE_MASK,
+                        n_pages, write, 1, pages, NULL);
+                /* negative error means that no page was pinned */
+                n = max(n, 0);
+                if (n != n_pages) {
+                        pr_err("got only %d of %d user pages\n", n, n_pages);
+                        while (n)
+                                put_page(pages[--n]);
+                        return -EFAULT;
+                }
         }
 
-        return vb2_mmap_pfn_range(vma, buf->dma_addr, buf->size,
-                                  &vb2_common_vm_ops, &buf->handler);
+        return 0;
 }
 
-static void *vb2_dma_contig_get_userptr(void *alloc_ctx, unsigned long vaddr,
-                                        unsigned long size, int write)
+static void vb2_dc_put_dirty_page(struct page *page)
 {
+        set_page_dirty_lock(page);
+        put_page(page);
+}
+
+static void vb2_dc_put_userptr(void *buf_priv)
+{
+        struct vb2_dc_buf *buf = buf_priv;
+        struct sg_table *sgt = buf->dma_sgt;
+
+        dma_unmap_sg(buf->dev, sgt->sgl, sgt->orig_nents, buf->dma_dir);
+        if (!vma_is_io(buf->vma))
+                vb2_dc_sgt_foreach_page(sgt, vb2_dc_put_dirty_page);
+
+        sg_free_table(sgt);
+        kfree(sgt);
+        vb2_put_vma(buf->vma);
+        kfree(buf);
+}
+
+static void *vb2_dc_get_userptr(void *alloc_ctx, unsigned long vaddr,
+        unsigned long size, int write)
+{
+        struct vb2_dc_conf *conf = alloc_ctx;
         struct vb2_dc_buf *buf;
+        unsigned long start;
+        unsigned long end;
+        unsigned long offset;
+        struct page **pages;
+        int n_pages;
+        int ret = 0;
         struct vm_area_struct *vma;
-        dma_addr_t dma_addr = 0;
-        int ret;
+        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);
+        }
 
         buf = kzalloc(sizeof *buf, GFP_KERNEL);
         if (!buf)
                 return ERR_PTR(-ENOMEM);
 
-        ret = vb2_get_contig_userptr(vaddr, size, &vma, &dma_addr);
+        buf->dev = conf->dev;
+        buf->dma_dir = write ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
+
+        start = vaddr & PAGE_MASK;
+        offset = vaddr & ~PAGE_MASK;
+        end = PAGE_ALIGN(vaddr + size);
+        n_pages = (end - start) >> PAGE_SHIFT;
+
+        pages = kmalloc(n_pages * sizeof(pages[0]), GFP_KERNEL);
+        if (!pages) {
+                ret = -ENOMEM;
+                pr_err("failed to allocate pages table\n");
+                goto fail_buf;
+        }
+
+        /* current->mm->mmap_sem is taken by videobuf2 core */
+        vma = find_vma(current->mm, vaddr);
+        if (!vma) {
+                pr_err("no vma for address %lu\n", vaddr);
+                ret = -EFAULT;
+                goto fail_pages;
+        }
+
+        if (vma->vm_end < vaddr + size) {
+                pr_err("vma at %lu is too small for %lu bytes\n", vaddr, size);
+                ret = -EFAULT;
+                goto fail_pages;
+        }
+
+        buf->vma = vb2_get_vma(vma);
+        if (!buf->vma) {
+                pr_err("failed to copy vma\n");
+                ret = -ENOMEM;
+                goto fail_pages;
+        }
+
+        /* extract page list from userspace mapping */
+        ret = vb2_dc_get_user_pages(start, pages, n_pages, vma, write);
         if (ret) {
-                printk(KERN_ERR "Failed acquiring VMA for vaddr 0x%08lx\n",
-                                vaddr);
-                kfree(buf);
-                return ERR_PTR(ret);
+                pr_err("failed to get user pages\n");
+                goto fail_vma;
+        }
+
+        sgt = kzalloc(sizeof(*sgt), GFP_KERNEL);
+        if (!sgt) {
+                pr_err("failed to allocate sg table\n");
+                ret = -ENOMEM;
+                goto fail_get_user_pages;
+        }
+
+        ret = sg_alloc_table_from_pages(sgt, pages, n_pages,
+                offset, size, GFP_KERNEL);
+        if (ret) {
+                pr_err("failed to initialize sg table\n");
+                goto fail_sgt;
         }
 
+        /* pages are no longer needed */
+        kfree(pages);
+        pages = NULL;
+
+        sgt->nents = dma_map_sg(buf->dev, sgt->sgl, sgt->orig_nents,
+                buf->dma_dir);
+        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->size = size;
-        buf->dma_addr = dma_addr;
-        buf->vma = vma;
+        buf->dma_sgt = sgt;
 
         return buf;
+
+fail_map_sg:
+        dma_unmap_sg(buf->dev, sgt->sgl, sgt->orig_nents, buf->dma_dir);
+
+fail_sgt_init:
+        if (!vma_is_io(buf->vma))
+                vb2_dc_sgt_foreach_page(sgt, put_page);
+        sg_free_table(sgt);
+
+fail_sgt:
+        kfree(sgt);
+
+fail_get_user_pages:
+        if (pages && !vma_is_io(buf->vma))
+                while (n_pages)
+                        put_page(pages[--n_pages]);
+
+fail_vma:
+        vb2_put_vma(buf->vma);
+
+fail_pages:
+        kfree(pages); /* kfree is NULL-proof */
+
+fail_buf:
+        kfree(buf);
+
+        return ERR_PTR(ret);
 }
 
-static void vb2_dma_contig_put_userptr(void *mem_priv)
+/*********************************************/
+/*       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 (!buf)
+        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_OR_NULL(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;
+
+        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;
+        }
 
-        vb2_put_vma(buf->vma);
+        if (WARN_ON(!sgt)) {
+                pr_err("dmabuf buffer is already unpinned\n");
+                return;
+        }
+
+        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(void *alloc_ctx, struct dma_buf *dbuf,
+        unsigned long size, int write)
+{
+        struct vb2_dc_conf *conf = alloc_ctx;
+        struct vb2_dc_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 = write ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
+        buf->size = size;
+        buf->db_attach = dba;
+
+        return buf;
+}
+
+/*********************************************/
+/*       DMA CONTIG exported functions       */
+/*********************************************/
+
 const struct vb2_mem_ops vb2_dma_contig_memops = {
-        .alloc          = vb2_dma_contig_alloc,
-        .put            = vb2_dma_contig_put,
-        .cookie         = vb2_dma_contig_cookie,
-        .vaddr          = vb2_dma_contig_vaddr,
-        .mmap           = vb2_dma_contig_mmap,
-        .get_userptr    = vb2_dma_contig_get_userptr,
-        .put_userptr    = vb2_dma_contig_put_userptr,
-        .num_users      = vb2_dma_contig_num_users,
+        .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);