Hi Tomasz,
Thanks for the patch.
Just a couple of small comments below.
On Tuesday 14 August 2012 17:34:50 Tomasz Stanislawski wrote:
> This patch adds support for exporting a dma-contig buffer using
> DMABUF interface.
>
> Signed-off-by: Tomasz Stanislawski <t.stanislaws@xxxxxxxxxxx>
> Signed-off-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
> ---
> drivers/media/video/videobuf2-dma-contig.c | 204 +++++++++++++++++++++++++
> 1 file changed, 204 insertions(+)
>
> diff --git a/drivers/media/video/videobuf2-dma-contig.c
> b/drivers/media/video/videobuf2-dma-contig.c index 7fc71a0..bb2b4ac8 100644
> --- a/drivers/media/video/videobuf2-dma-contig.c
> +++ b/drivers/media/video/videobuf2-dma-contig.c
[snip]
> +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 */
Why isn't this operation serialized by the dma-buf core itself ?
> + 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;
> +}
[snip]
> +static int vb2_dc_dmabuf_ops_mmap(struct dma_buf *dbuf,
> + struct vm_area_struct *vma)
> +{
> + /* Dummy support for mmap */
> + return -ENOTTY;
What about calling the dma-contig mmap handler here ? Is there a specific
reason why you haven't implemented mmap support for dmabuf ?
> +}
> +
> +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 ERR_PTR(-ENOMEM);
> + }
> +
> + 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 ERR_PTR(ret);
> + }
As this function is only used below, where the exact value of the error code
is ignored, what about just returning NULL on failure ? Another option is to
return the error code in vb2_dc_get_dmabuf (not sure if that would be useful
though).
> +
> + return sgt;
> +}
> +
> +static struct dma_buf *vb2_dc_get_dmabuf(void *buf_priv)
> +{
> + struct vb2_dc_buf *buf = buf_priv;
> + struct dma_buf *dbuf;
> + struct sg_table *sgt = buf->sgt_base;
> +
> + if (!sgt)
> + sgt = vb2_dc_get_base_sgt(buf);
> + if (WARN_ON(IS_ERR(sgt)))
> + return NULL;
> +
> + /* cache base sgt for future use */
> + buf->sgt_base = sgt;
You can move this assignment inside the first if, there's no need to execute
it every time. The WARN_ON can also be moved inside the first if, as buf-
>sgt_base will either be NULL or valid. You can then get rid of the sgt
variable initialization by testing if (!buf->sgt_base).
> + 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;
> +}
--
Regards,
Laurent Pinchart
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