Hi Tomasz,
Thanks for the patch.
On Friday 13 April 2012 17:47:50 Tomasz Stanislawski wrote:
> From: Andrzej Pietrasiewicz <andrzej.p@xxxxxxxxxxx>
>
> This patch introduces usage of dma_map_sg to map memory behind
> a userspace pointer to a device as dma-contiguous mapping.
>
> Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@xxxxxxxxxxx>
> Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> [bugfixing]
> Signed-off-by: Kamil Debski <k.debski@xxxxxxxxxxx>
> [bugfixing]
> Signed-off-by: Tomasz Stanislawski <t.stanislaws@xxxxxxxxxxx>
> [add sglist subroutines/code refactoring]
> Signed-off-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
> ---
> drivers/media/video/videobuf2-dma-contig.c | 287 +++++++++++++++++++++++--
> 1 files changed, 270 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/media/video/videobuf2-dma-contig.c
> b/drivers/media/video/videobuf2-dma-contig.c index 476e536..3a1e314 100644
> --- a/drivers/media/video/videobuf2-dma-contig.c
> +++ b/drivers/media/video/videobuf2-dma-contig.c
[snip]
> +static struct sg_table *vb2_dc_pages_to_sgt(struct page **pages,
> + unsigned int n_pages, unsigned long offset, unsigned long size)
> +{
> + struct sg_table *sgt;
> + unsigned int chunks;
> + unsigned int i;
> + unsigned int cur_page;
> + int ret;
> + struct scatterlist *s;
> + unsigned int offset_end = n_pages * PAGE_SIZE - size;
Shouldn't offset_end be equal to n_page * PAGE_SIZE - size - offset ?
> + sgt = kzalloc(sizeof *sgt, GFP_KERNEL);
> + if (!sgt)
> + return ERR_PTR(-ENOMEM);
> +
> + /* compute number of chunks */
> + chunks = 1;
> + for (i = 1; i < n_pages; ++i)
> + if (pages[i] != pages[i - 1] + 1)
> + ++chunks;
> +
> + ret = sg_alloc_table(sgt, chunks, GFP_KERNEL);
> + if (ret) {
> + kfree(sgt);
> + return ERR_PTR(-ENOMEM);
> + }
> +
> + /* merging chunks and putting them into the scatterlist */
> + cur_page = 0;
> + for_each_sg(sgt->sgl, s, sgt->orig_nents, i) {
> + size_t size = PAGE_SIZE;
This will shadow the size parameter, it's a bit confusing. You could rename it
chunk_size.
> + unsigned int j;
> +
> + for (j = cur_page + 1; j < n_pages; ++j) {
> + if (pages[j] != pages[j - 1] + 1)
> + break;
> + size += PAGE_SIZE;
> + }
> + /* cut offset if chunk starts at the first page */
> + if (cur_page == 0)
> + size -= offset;
> + /* cut offset_end if chunk ends at the last page */
> + if (j == n_pages)
> + size -= offset_end;
> +
> + sg_set_page(s, pages[cur_page], size, offset);
> + offset = 0;
What about just
chunk_size -= offset;
sg_set_page(s, pages[cur_page], min(size, chunk_size), offset);
size -= chunk_size;
offset = 0;
You could then remove the offset_end calculation above.
> + cur_page = j;
> + }
> +
> + return sgt;
> +}
--
Regards,
Laurent Pinchart
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