linux-kernel - Re: [PATCH v9 31/32] media: pci: fix common ALSA DMA-mapping related codes

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Message-ID: <925232f3-7371-c7eb-ad31-4b041cbbca4f@arm.com>
Date:   Tue, 1 Sep 2020 21:24:46 +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>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org
Subject: Re: [PATCH v9 31/32] media: pci: fix common ALSA DMA-mapping related
 codes

On 2020-08-26 07:33, Marek Szyprowski wrote:
> The Documentation/DMA-API-HOWTO.txt states that dma_map_sg returns the
> numer of the created entries in the DMA address space. However the
> subsequent calls to dma_sync_sg_for_{device,cpu} and dma_unmap_sg must be
> called with the original number of entries passed to dma_map_sg. The
> sg_table->nents in turn holds the result of the dma_map_sg call as stated
> in include/linux/scatterlist.h. Adapt the code to obey those rules.
> 
> Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
> ---
>   drivers/media/pci/cx23885/cx23885-alsa.c | 2 +-
>   drivers/media/pci/cx25821/cx25821-alsa.c | 2 +-
>   drivers/media/pci/cx88/cx88-alsa.c       | 2 +-
>   drivers/media/pci/saa7134/saa7134-alsa.c | 2 +-
>   4 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/media/pci/cx23885/cx23885-alsa.c b/drivers/media/pci/cx23885/cx23885-alsa.c
> index df44ed7393a0..3f366e4e4685 100644
> --- a/drivers/media/pci/cx23885/cx23885-alsa.c
> +++ b/drivers/media/pci/cx23885/cx23885-alsa.c
> @@ -129,7 +129,7 @@ static int cx23885_alsa_dma_unmap(struct cx23885_audio_dev *dev)
>   	if (!buf->sglen)
>   		return 0;
>   
> -	dma_unmap_sg(&dev->pci->dev, buf->sglist, buf->sglen, PCI_DMA_FROMDEVICE);
> +	dma_unmap_sg(&dev->pci->dev, buf->sglist, buf->nr_pages, PCI_DMA_FROMDEVICE);

If we're touching these lines anyway, we should update them to use the 
modern DMA_FROM_DEVICE definitions too.

Robin.

>   	buf->sglen = 0;
>   	return 0;
>   }
> diff --git a/drivers/media/pci/cx25821/cx25821-alsa.c b/drivers/media/pci/cx25821/cx25821-alsa.c
> index 301616426d8a..c40304d33776 100644
> --- a/drivers/media/pci/cx25821/cx25821-alsa.c
> +++ b/drivers/media/pci/cx25821/cx25821-alsa.c
> @@ -193,7 +193,7 @@ static int cx25821_alsa_dma_unmap(struct cx25821_audio_dev *dev)
>   	if (!buf->sglen)
>   		return 0;
>   
> -	dma_unmap_sg(&dev->pci->dev, buf->sglist, buf->sglen, PCI_DMA_FROMDEVICE);
> +	dma_unmap_sg(&dev->pci->dev, buf->sglist, buf->nr_pages, PCI_DMA_FROMDEVICE);
>   	buf->sglen = 0;
>   	return 0;
>   }
> diff --git a/drivers/media/pci/cx88/cx88-alsa.c b/drivers/media/pci/cx88/cx88-alsa.c
> index 7d7aceecc985..3c6fe6ceb0b7 100644
> --- a/drivers/media/pci/cx88/cx88-alsa.c
> +++ b/drivers/media/pci/cx88/cx88-alsa.c
> @@ -332,7 +332,7 @@ static int cx88_alsa_dma_unmap(struct cx88_audio_dev *dev)
>   	if (!buf->sglen)
>   		return 0;
>   
> -	dma_unmap_sg(&dev->pci->dev, buf->sglist, buf->sglen,
> +	dma_unmap_sg(&dev->pci->dev, buf->sglist, buf->nr_pages,
>   		     PCI_DMA_FROMDEVICE);
>   	buf->sglen = 0;
>   	return 0;
> diff --git a/drivers/media/pci/saa7134/saa7134-alsa.c b/drivers/media/pci/saa7134/saa7134-alsa.c
> index 544ca57eee75..398c47ff473d 100644
> --- a/drivers/media/pci/saa7134/saa7134-alsa.c
> +++ b/drivers/media/pci/saa7134/saa7134-alsa.c
> @@ -313,7 +313,7 @@ static int saa7134_alsa_dma_unmap(struct saa7134_dev *dev)
>   	if (!dma->sglen)
>   		return 0;
>   
> -	dma_unmap_sg(&dev->pci->dev, dma->sglist, dma->sglen, PCI_DMA_FROMDEVICE);
> +	dma_unmap_sg(&dev->pci->dev, dma->sglist, dma->nr_pages, PCI_DMA_FROMDEVICE);
>   	dma->sglen = 0;
>   	return 0;
>   }
>