Re: [PATCH v2 1/3] media/videobuf2-dma-sg: Fix handling of sg_table structure

Marek Szyprowski
2015-02-11T10:43:07Z

Hello,

On 2015-02-11 11:33, Ricardo Ribalda Delgado wrote:
> When sg_alloc_table_from_pages() does not fail it returns a sg_table
> structure with nents and nents_orig initialized to the same value.
>
> dma_map_sg returns the number of areas mapped by the hardware,
> which could be different than the areas given as an input.
> The output must be saved to nent.
>
> The output of dma_map, should be used to transverse the scatter list.
>
> dma_unmap_sg needs the value passed to dma_map_sg (nents_orig).
>
> sg_free_tables uses also orig_nent.
>
> This patch fix the file to follow this paradigm.
>
> Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>

Reviewed-by: Marek Szyprowski <m.szyprowski@samsung.com>

I would also consider sending it to stable.

> ---
> drivers/media/v4l2-core/videobuf2-dma-sg.c | 22 +++++++++++++---------
> 1 file changed, 13 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/media/v4l2-core/videobuf2-dma-sg.c b/drivers/media/v4l2-core/videobuf2-dma-sg.c
> index b1838ab..40c330f 100644
> --- a/drivers/media/v4l2-core/videobuf2-dma-sg.c
> +++ b/drivers/media/v4l2-core/videobuf2-dma-sg.c
> @@ -147,8 +147,9 @@ static void *vb2_dma_sg_alloc(void *alloc_ctx, unsigned long size,
> * No need to sync to the device, this will happen later when the
> * prepare() memop is called.
> */
> - if (dma_map_sg_attrs(buf->dev, sgt->sgl, sgt->nents,
> - buf->dma_dir, &attrs) == 0)
> + sgt->nents = dma_map_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents,
> + buf->dma_dir, &attrs);
> + if (!sgt->nents)
> goto fail_map;
>
> buf->handler.refcount = &buf->refcount;
> @@ -187,7 +188,7 @@ static void vb2_dma_sg_put(void *buf_priv)
> dma_set_attr(DMA_ATTR_SKIP_CPU_SYNC, &attrs);
> dprintk(1, "%s: Freeing buffer of %d pages\n", __func__,
> buf->num_pages);
> - dma_unmap_sg_attrs(buf->dev, sgt->sgl, sgt->nents,
> + dma_unmap_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents,
> buf->dma_dir, &attrs);
> if (buf->vaddr)
> vm_unmap_ram(buf->vaddr, buf->num_pages);
> @@ -314,9 +315,11 @@ static void *vb2_dma_sg_get_userptr(void *alloc_ctx, unsigned long vaddr,
> * No need to sync to the device, this will happen later when the
> * prepare() memop is called.
> */
> - if (dma_map_sg_attrs(buf->dev, sgt->sgl, sgt->nents,
> - buf->dma_dir, &attrs) == 0)
> + sgt->nents = dma_map_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents,
> + buf->dma_dir, &attrs);
> + if (!sgt->nents)
> goto userptr_fail_map;
> +
> return buf;
>
> userptr_fail_map:
> @@ -351,7 +354,8 @@ static void vb2_dma_sg_put_userptr(void *buf_priv)
>
> dprintk(1, "%s: Releasing userspace buffer of %d pages\n",
> __func__, buf->num_pages);
> - dma_unmap_sg_attrs(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir, &attrs);
> + dma_unmap_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents, buf->dma_dir,
> + &attrs);
> if (buf->vaddr)
> vm_unmap_ram(buf->vaddr, buf->num_pages);
> sg_free_table(buf->dma_sgt);
> @@ -502,7 +506,6 @@ static struct sg_table *vb2_dma_sg_dmabuf_ops_map(
> /* stealing dmabuf mutex to serialize map/unmap operations */
> struct mutex *lock = &db_attach->dmabuf->lock;
> struct sg_table *sgt;
> - int ret;
>
> mutex_lock(lock);
>
> @@ -521,8 +524,9 @@ static struct sg_table *vb2_dma_sg_dmabuf_ops_map(
> }
>
> /* mapping to the client with new direction */
> - ret = dma_map_sg(db_attach->dev, sgt->sgl, sgt->orig_nents, dma_dir);
> - if (ret <= 0) {
> + 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);

Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland