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

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Message-id: <54DB3232.40000@samsung.com>
Date:	Wed, 11 Feb 2015 11:42:58 +0100
From:	Marek Szyprowski <m.szyprowski@...sung.com>
To:	Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>,
	Pawel Osciak <pawel@...iak.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Mauro Carvalho Chehab <mchehab@....samsung.com>,
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
	Hans Verkuil <hans.verkuil@...co.com>
Subject: Re: [PATCH v2 1/3] media/videobuf2-dma-sg: Fix handling of sg_table
 structure

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@...il.com>

Reviewed-by: Marek Szyprowski <m.szyprowski@...sung.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

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