Re: [PATCH v10 30/30] videobuf2: use sgtable-based scatterlist wrappers

[Tomasz Figa <tfiga@chromium.org>]

Hi Marek,

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?

> @@ -455,8 +453,8 @@ static void vb2_dc_put_userptr(void *buf_priv)
>                  * No need to sync to CPU, it's already synced to the CPU
>                  * since the finish() memop will have been called before this.
>                  */
> -               dma_unmap_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents,
> -                                  buf->dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
> +               dma_unmap_sgtable(buf->dev, sgt, buf->dma_dir,
> +                                 DMA_ATTR_SKIP_CPU_SYNC);
>                 pages = frame_vector_pages(buf->vec);
>                 /* sgt should exist only if vector contains pages... */
>                 BUG_ON(IS_ERR(pages));
> @@ -553,9 +551,8 @@ static void *vb2_dc_get_userptr(struct device *dev, unsigned long vaddr,
>          * No need to sync to the device, this will happen later when the
>          * prepare() memop is called.
>          */
> -       sgt->nents = dma_map_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents,
> -                                     buf->dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
> -       if (sgt->nents <= 0) {
> +       if (dma_map_sgtable(buf->dev, sgt, buf->dma_dir,
> +                           DMA_ATTR_SKIP_CPU_SYNC)) {
>                 pr_err("failed to map scatterlist\n");
>                 ret = -EIO;

Ditto.

>                 goto fail_sgt_init;
> @@ -577,8 +574,7 @@ static void *vb2_dc_get_userptr(struct device *dev, unsigned long vaddr,
>         return buf;
>
>  fail_map_sg:
> -       dma_unmap_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents,
> -                          buf->dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
> +       dma_unmap_sgtable(buf->dev, sgt, buf->dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
>
>  fail_sgt_init:
>         sg_free_table(sgt);
> diff --git a/drivers/media/common/videobuf2/videobuf2-dma-sg.c b/drivers/media/common/videobuf2/videobuf2-dma-sg.c
> index 0a40e00f0d7e..0dd3b19025e0 100644
> --- a/drivers/media/common/videobuf2/videobuf2-dma-sg.c
> +++ b/drivers/media/common/videobuf2/videobuf2-dma-sg.c
> @@ -148,9 +148,8 @@ static void *vb2_dma_sg_alloc(struct device *dev, unsigned long dma_attrs,
>          * No need to sync to the device, this will happen later when the
>          * prepare() memop is called.
>          */
> -       sgt->nents = dma_map_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents,
> -                                     buf->dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
> -       if (!sgt->nents)
> +       if (dma_map_sgtable(buf->dev, sgt, buf->dma_dir,
> +                           DMA_ATTR_SKIP_CPU_SYNC))
>                 goto fail_map;
>

Ditto.

>         buf->handler.refcount = &buf->refcount;
> @@ -186,8 +185,8 @@ static void vb2_dma_sg_put(void *buf_priv)
>         if (refcount_dec_and_test(&buf->refcount)) {
>                 dprintk(1, "%s: Freeing buffer of %d pages\n", __func__,
>                         buf->num_pages);
> -               dma_unmap_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents,
> -                                  buf->dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
> +               dma_unmap_sgtable(buf->dev, sgt, buf->dma_dir,
> +                                 DMA_ATTR_SKIP_CPU_SYNC);
>                 if (buf->vaddr)
>                         vm_unmap_ram(buf->vaddr, buf->num_pages);
>                 sg_free_table(buf->dma_sgt);
> @@ -204,8 +203,7 @@ static void vb2_dma_sg_prepare(void *buf_priv)
>         struct vb2_dma_sg_buf *buf = buf_priv;
>         struct sg_table *sgt = buf->dma_sgt;
>
> -       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_dma_sg_finish(void *buf_priv)
> @@ -213,7 +211,7 @@ static void vb2_dma_sg_finish(void *buf_priv)
>         struct vb2_dma_sg_buf *buf = buf_priv;
>         struct sg_table *sgt = buf->dma_sgt;
>
> -       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);
>  }
>
>  static void *vb2_dma_sg_get_userptr(struct device *dev, unsigned long vaddr,
> @@ -256,9 +254,8 @@ static void *vb2_dma_sg_get_userptr(struct device *dev, unsigned long vaddr,
>          * No need to sync to the device, this will happen later when the
>          * prepare() memop is called.
>          */
> -       sgt->nents = dma_map_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents,
> -                                     buf->dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
> -       if (!sgt->nents)
> +       if (dma_map_sgtable(buf->dev, sgt, buf->dma_dir,
> +                           DMA_ATTR_SKIP_CPU_SYNC))
>                 goto userptr_fail_map;
>

Ditto.

>         return buf;
> @@ -284,8 +281,7 @@ 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->orig_nents, buf->dma_dir,
> -                          DMA_ATTR_SKIP_CPU_SYNC);
> +       dma_unmap_sgtable(buf->dev, sgt, buf->dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
>         if (buf->vaddr)
>                 vm_unmap_ram(buf->vaddr, buf->num_pages);
>         sg_free_table(buf->dma_sgt);
> @@ -408,8 +404,7 @@ static void vb2_dma_sg_dmabuf_ops_detach(struct dma_buf *dbuf,
>
>         /* release the scatterlist cache */
>         if (attach->dma_dir != DMA_NONE)
> -               dma_unmap_sg(db_attach->dev, sgt->sgl, sgt->orig_nents,
> -                       attach->dma_dir);
> +               dma_unmap_sgtable(db_attach->dev, sgt, attach->dma_dir, 0);
>         sg_free_table(sgt);
>         kfree(attach);
>         db_attach->priv = NULL;
> @@ -434,15 +429,12 @@ static struct sg_table *vb2_dma_sg_dmabuf_ops_map(
>
>         /* release any previous cache */
>         if (attach->dma_dir != DMA_NONE) {
> -               dma_unmap_sg(db_attach->dev, sgt->sgl, sgt->orig_nents,
> -                       attach->dma_dir);
> +               dma_unmap_sgtable(db_attach->dev, sgt, attach->dma_dir, 0);
>                 attach->dma_dir = DMA_NONE;
>         }
>
>         /* mapping to the client with new direction */
> -       sgt->nents = dma_map_sg(db_attach->dev, sgt->sgl, sgt->orig_nents,
> -                               dma_dir);
> -       if (!sgt->nents) {
> +       if (dma_map_sgtable(db_attach->dev, sgt, dma_dir, 0)) {
>                 pr_err("failed to map scatterlist\n");
>                 mutex_unlock(lock);
>                 return ERR_PTR(-EIO);

Ditto.

> diff --git a/drivers/media/common/videobuf2/videobuf2-vmalloc.c b/drivers/media/common/videobuf2/videobuf2-vmalloc.c
> index c66fda4a65e4..bf5ac63a5742 100644
> --- a/drivers/media/common/videobuf2/videobuf2-vmalloc.c
> +++ b/drivers/media/common/videobuf2/videobuf2-vmalloc.c
> @@ -229,7 +229,7 @@ static int vb2_vmalloc_dmabuf_ops_attach(struct dma_buf *dbuf,
>                 kfree(attach);
>                 return ret;
>         }
> -       for_each_sg(sgt->sgl, sg, sgt->nents, i) {
> +       for_each_sgtable_sg(sgt, sg, i) {
>                 struct page *page = vmalloc_to_page(vaddr);
>
>                 if (!page) {
> @@ -259,8 +259,7 @@ static void vb2_vmalloc_dmabuf_ops_detach(struct dma_buf *dbuf,
>
>         /* release the scatterlist cache */
>         if (attach->dma_dir != DMA_NONE)
> -               dma_unmap_sg(db_attach->dev, sgt->sgl, sgt->orig_nents,
> -                       attach->dma_dir);
> +               dma_unmap_sgtable(db_attach->dev, sgt, attach->dma_dir, 0);
>         sg_free_table(sgt);
>         kfree(attach);
>         db_attach->priv = NULL;
> @@ -285,15 +284,12 @@ static struct sg_table *vb2_vmalloc_dmabuf_ops_map(
>
>         /* release any previous cache */
>         if (attach->dma_dir != DMA_NONE) {
> -               dma_unmap_sg(db_attach->dev, sgt->sgl, sgt->orig_nents,
> -                       attach->dma_dir);
> +               dma_unmap_sgtable(db_attach->dev, sgt, attach->dma_dir, 0);
>                 attach->dma_dir = DMA_NONE;
>         }
>
>         /* mapping to the client with new direction */
> -       sgt->nents = dma_map_sg(db_attach->dev, sgt->sgl, sgt->orig_nents,
> -                               dma_dir);
> -       if (!sgt->nents) {
> +       if (dma_map_sgtable(db_attach->dev, sgt, dma_dir, 0)) {
>                 pr_err("failed to map scatterlist\n");
>                 mutex_unlock(lock);
>                 return ERR_PTR(-EIO);

Ditto.

Best regards,
Tomasz
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