[PATCH v4 37/38] media: pci: fix common ALSA DMA-mapping related codes

[Marek Szyprowski]

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@xxxxxxxxxxx>
---
For more information, see '[PATCH v4 00/38] DRM: fix struct sg_table nents
vs. orig_nents misuse' thread:
https://lore.kernel.org/dri-devel/20200512085710.14688-1-m.szyprowski@xxxxxxxxxxx/T/
---
 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 df44ed7..3f366e4 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);
 	buf->sglen = 0;
 	return 0;
 }
diff --git a/drivers/media/pci/cx25821/cx25821-alsa.c b/drivers/media/pci/cx25821/cx25821-alsa.c
index 3016164..c40304d 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 7d7acee..3c6fe6c 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 544ca57..398c47f 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;
 }
-- 
1.9.1