Re: [REVIEWv7 PATCH 09/12] vb2-vmalloc: add support for dmabuf exports

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On Tue, Nov 18, 2014 at 9:51 PM, Hans Verkuil <hverkuil@xxxxxxxxx> wrote:
> From: Hans Verkuil <hansverk@xxxxxxxxx>
>
> Add support for DMABUF exporting to the vb2-vmalloc implementation.
>
> All memory models now have support for both importing and exporting of DMABUFs.
>
> Signed-off-by: Hans Verkuil <hansverk@xxxxxxxxx>

Acked-by: Pawel Osciak <pawel@xxxxxxxxxx>

> ---
>  drivers/media/v4l2-core/videobuf2-vmalloc.c | 171 ++++++++++++++++++++++++++++
>  1 file changed, 171 insertions(+)
>
> diff --git a/drivers/media/v4l2-core/videobuf2-vmalloc.c b/drivers/media/v4l2-core/videobuf2-vmalloc.c
> index bba2460..3966b12 100644
> --- a/drivers/media/v4l2-core/videobuf2-vmalloc.c
> +++ b/drivers/media/v4l2-core/videobuf2-vmalloc.c
> @@ -213,6 +213,176 @@ static int vb2_vmalloc_mmap(void *buf_priv, struct vm_area_struct *vma)
>  }
>
>  /*********************************************/
> +/*         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;
> +       int ret;
> +
> +       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 */
> +       ret = dma_map_sg(db_attach->dev, sgt->sgl, sgt->orig_nents, dma_dir);
> +       if (ret <= 0) {
> +               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;
> +
> +       if (WARN_ON(!buf->vaddr))
> +               return NULL;
> +
> +       dbuf = dma_buf_export(buf, &vb2_vmalloc_dmabuf_ops, buf->size, flags, NULL);
> +       if (IS_ERR(dbuf))
> +               return NULL;
> +
> +       /* dmabuf keeps reference to vb2 buffer */
> +       atomic_inc(&buf->refcount);
> +
> +       return dbuf;
> +}
> +
> +/*********************************************/
>  /*       callbacks for DMABUF buffers        */
>  /*********************************************/
>
> @@ -268,6 +438,7 @@ const struct vb2_mem_ops vb2_vmalloc_memops = {
>         .put            = vb2_vmalloc_put,
>         .get_userptr    = vb2_vmalloc_get_userptr,
>         .put_userptr    = vb2_vmalloc_put_userptr,
> +       .get_dmabuf     = vb2_vmalloc_get_dmabuf,
>         .map_dmabuf     = vb2_vmalloc_map_dmabuf,
>         .unmap_dmabuf   = vb2_vmalloc_unmap_dmabuf,
>         .attach_dmabuf  = vb2_vmalloc_attach_dmabuf,
> --
> 2.1.1
>



-- 
Best regards,
Pawel Osciak
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