Re: [PATCHv10 20/26] v4l: vb2-dma-contig: add support for DMABUF exporting

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Tomasz,

On Wednesday 10 October 2012 16:46:39 Tomasz Stanislawski wrote:
> This patch adds support for exporting a dma-contig buffer using
> DMABUF interface.
> 
> Signed-off-by: Tomasz Stanislawski <t.stanislaws@samsung.com>
> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
> Acked-by: Hans Verkuil <hans.verkuil@cisco.com>

Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

> ---
>  drivers/media/v4l2-core/videobuf2-dma-contig.c |  200 +++++++++++++++++++++
>  1 file changed, 200 insertions(+)
> 
> diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c
> b/drivers/media/v4l2-core/videobuf2-dma-contig.c index 0e065ce..b138b5c
> 100644
> --- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
> +++ b/drivers/media/v4l2-core/videobuf2-dma-contig.c
> @@ -36,6 +36,7 @@ struct vb2_dc_buf {
>  	/* MMAP related */
>  	struct vb2_vmarea_handler	handler;
>  	atomic_t			refcount;
> +	struct sg_table			*sgt_base;
> 
>  	/* USERPTR related */
>  	struct vm_area_struct		*vma;
> @@ -142,6 +143,10 @@ static void vb2_dc_put(void *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);
>  	kfree(buf);
>  }
> @@ -213,6 +218,200 @@ static int vb2_dc_mmap(void *buf_priv, struct
> vm_area_struct *vma) }
> 
>  /*********************************************/
> +/*         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_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->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->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 int vb2_dc_dmabuf_ops_mmap(struct dma_buf *dbuf,
> +	struct vm_area_struct *vma)
> +{
> +	return vb2_dc_mmap(dbuf->priv, vma);
> +}
> +
> +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 struct dma_buf *vb2_dc_get_dmabuf(void *buf_priv)
> +{
> +	struct vb2_dc_buf *buf = buf_priv;
> +	struct dma_buf *dbuf;
> +
> +	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       */
>  /*********************************************/
> 
> @@ -519,6 +718,7 @@ static void *vb2_dc_attach_dmabuf(void *alloc_ctx,
> struct dma_buf *dbuf, 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,
-- 
Regards,

Laurent Pinchart