Hi Tomasz,

On 07.09.2020 15:07, Tomasz Figa wrote:

On Fri, Sep 4, 2020 at 3:35 PM Marek Szyprowski m.szyprowski@samsung.com wrote:

...

Use recently introduced common wrappers operating directly on the struct sg_table objects and scatterlist page iterators to make the code a bit more compact, robust, easier to follow and copy/paste safe.

No functional change, because the code already properly did all the scatterlist related calls.

Signed-off-by: Marek Szyprowski m.szyprowski@samsung.com Reviewed-by: Robin Murphy robin.murphy@arm.com

---

.../common/videobuf2/videobuf2-dma-contig.c | 34 ++++++++----------- .../media/common/videobuf2/videobuf2-dma-sg.c | 32 +++++++---------- .../common/videobuf2/videobuf2-vmalloc.c | 12 +++---- 3 files changed, 31 insertions(+), 47 deletions(-)

Thanks for the patch! Please see my comments inline.

...

diff --git a/drivers/media/common/videobuf2/videobuf2-dma-contig.c b/drivers/media/common/videobuf2/videobuf2-dma-contig.c index ec3446cc45b8..1b242d844dde 100644 --- a/drivers/media/common/videobuf2/videobuf2-dma-contig.c +++ b/drivers/media/common/videobuf2/videobuf2-dma-contig.c @@ -58,10 +58,10 @@ static unsigned long vb2_dc_get_contiguous_size(struct sg_table *sgt) unsigned int i; unsigned long size = 0;

•   for_each_sg(sgt->sgl, s, sgt->nents, i) {
  

•   for_each_sgtable_dma_sg(sgt, s, i) {
             if (sg_dma_address(s) != expected)
                     break;
  

•           expected = sg_dma_address(s) + sg_dma_len(s);
  

•           expected += sg_dma_len(s);
             size += sg_dma_len(s);
     }
     return size;
  

@@ -103,8 +103,7 @@ static void vb2_dc_prepare(void *buf_priv) if (!sgt) return;

•   dma_sync_sg_for_device(buf->dev, sgt->sgl, sgt->orig_nents,
  

•                          buf->dma_dir);
  

•   dma_sync_sgtable_for_device(buf->dev, sgt, buf->dma_dir);
  

  }

  static void vb2_dc_finish(void *buf_priv)

@@ -115,7 +114,7 @@ static void vb2_dc_finish(void *buf_priv) if (!sgt) return;

•   dma_sync_sg_for_cpu(buf->dev, sgt->sgl, sgt->orig_nents, buf->dma_dir);
  

•   dma_sync_sgtable_for_cpu(buf->dev, sgt, buf->dma_dir);
  

  }

  /*********************************************/

@@ -275,8 +274,8 @@ static void vb2_dc_dmabuf_ops_detach(struct dma_buf *dbuf, * memory locations do not require any explicit cache * maintenance prior or after being used by the device. */

•           dma_unmap_sg_attrs(db_attach->dev, sgt->sgl, sgt->orig_nents,
  

•                              attach->dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
  

•           dma_unmap_sgtable(db_attach->dev, sgt, attach->dma_dir,
  

•                             DMA_ATTR_SKIP_CPU_SYNC);
     sg_free_table(sgt);
     kfree(attach);
     db_attach->priv = NULL;
  

@@ -301,8 +300,8 @@ static struct sg_table *vb2_dc_dmabuf_ops_map(

     /* release any previous cache */
     if (attach->dma_dir != DMA_NONE) {

•           dma_unmap_sg_attrs(db_attach->dev, sgt->sgl, sgt->orig_nents,
  

•                              attach->dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
  

•           dma_unmap_sgtable(db_attach->dev, sgt, attach->dma_dir,
  

•                             DMA_ATTR_SKIP_CPU_SYNC);
             attach->dma_dir = DMA_NONE;
     }
  
  

@@ -310,9 +309,8 @@ static struct sg_table *vb2_dc_dmabuf_ops_map( * mapping to the client with new direction, no cache sync * required see comment in vb2_dc_dmabuf_ops_detach() */

•   sgt->nents = dma_map_sg_attrs(db_attach->dev, sgt->sgl, sgt->orig_nents,
  

•                                 dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
  

•   if (!sgt->nents) {
  

•   if (dma_map_sgtable(db_attach->dev, sgt, dma_dir,
  

•                       DMA_ATTR_SKIP_CPU_SYNC)) {
             pr_err("failed to map scatterlist\n");
             mutex_unlock(lock);
             return ERR_PTR(-EIO);
  

As opposed to dma_map_sg_attrs(), dma_map_sgtable() now returns an error code on its own. Is it expected to ignore it and return -EIO?

Those errors are more or less propagated to userspace and -EIO has been already widely documented in V4L2 documentation as the error code for the most of the V4L2 ioctls. I don't want to change it. A possible -EINVAL returned from dma_map_sgtable() was just one of the 'generic' error codes, not very descriptive in that case. Probably the main problem here is that dma_map_sg() and friend doesn't return any error codes...

...

Best regards