linux-kernel - Re: [PATCH v9 10/32] drm: mediatek: use common helper for a scatterlist contiguity check

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Date:   Tue, 1 Sep 2020 19:44:34 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Marek Szyprowski <m.szyprowski@...sung.com>,
        dri-devel@...ts.freedesktop.org, iommu@...ts.linux-foundation.org,
        linaro-mm-sig@...ts.linaro.org, linux-kernel@...r.kernel.org
Cc:     Christoph Hellwig <hch@....de>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        linux-arm-kernel@...ts.infradead.org,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Chun-Kuang Hu <chunkuang.hu@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH v9 10/32] drm: mediatek: use common helper for a
 scatterlist contiguity check

On 2020-08-26 07:32, Marek Szyprowski wrote:
> Use common helper for checking the contiguity of the imported dma-buf and
> do this check before allocating resources, so the error path is simpler.

Reviewed-by: Robin Murphy <robin.murphy@....com>

> Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
> ---
>   drivers/gpu/drm/mediatek/mtk_drm_gem.c | 28 ++++++--------------------
>   1 file changed, 6 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_gem.c b/drivers/gpu/drm/mediatek/mtk_drm_gem.c
> index 6190cc3b7b0d..3654ec732029 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_gem.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_gem.c
> @@ -212,37 +212,21 @@ struct drm_gem_object *mtk_gem_prime_import_sg_table(struct drm_device *dev,
>   			struct dma_buf_attachment *attach, struct sg_table *sg)
>   {
>   	struct mtk_drm_gem_obj *mtk_gem;
> -	int ret;
> -	struct scatterlist *s;
> -	unsigned int i;
> -	dma_addr_t expected;
>   
> -	mtk_gem = mtk_drm_gem_init(dev, attach->dmabuf->size);
> +	/* check if the entries in the sg_table are contiguous */
> +	if (drm_prime_get_contiguous_size(sg) < attach->dmabuf->size) {
> +		DRM_ERROR("sg_table is not contiguous");
> +		return ERR_PTR(-EINVAL);
> +	}
>   
> +	mtk_gem = mtk_drm_gem_init(dev, attach->dmabuf->size);
>   	if (IS_ERR(mtk_gem))
>   		return ERR_CAST(mtk_gem);
>   
> -	expected = sg_dma_address(sg->sgl);
> -	for_each_sg(sg->sgl, s, sg->nents, i) {
> -		if (!sg_dma_len(s))
> -			break;
> -
> -		if (sg_dma_address(s) != expected) {
> -			DRM_ERROR("sg_table is not contiguous");
> -			ret = -EINVAL;
> -			goto err_gem_free;
> -		}
> -		expected = sg_dma_address(s) + sg_dma_len(s);
> -	}
> -
>   	mtk_gem->dma_addr = sg_dma_address(sg->sgl);
>   	mtk_gem->sg = sg;
>   
>   	return &mtk_gem->base;
> -
> -err_gem_free:
> -	kfree(mtk_gem);
> -	return ERR_PTR(ret);
>   }
>   
>   void *mtk_drm_gem_prime_vmap(struct drm_gem_object *obj)
>