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SubjectRe: [PATCH 3/3] videobuf2: replace a layering violation with dma_map_resource
Em Fri, 11 Jan 2019 19:17:31 +0100
Christoph Hellwig <hch@lst.de> escreveu:

> vb2_dc_get_userptr pokes into arm direct mapping details to get the
> resemblance of a dma address for a a physical address that does is
> not backed by a page struct. Not only is this not portable to other
> architectures with dma direct mapping offsets, but also not to uses
> of IOMMUs of any kind. Switch to the proper dma_map_resource /
> dma_unmap_resource interface instead.

Makes sense to me. I'm assuming that you'll be pushing it together
with other mm patches, so:

Acked-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> .../common/videobuf2/videobuf2-dma-contig.c | 41 ++++---------------
> 1 file changed, 9 insertions(+), 32 deletions(-)
>
> diff --git a/drivers/media/common/videobuf2/videobuf2-dma-contig.c b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
> index aff0ab7bf83d..82389aead6ed 100644
> --- a/drivers/media/common/videobuf2/videobuf2-dma-contig.c
> +++ b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
> @@ -439,42 +439,14 @@ static void vb2_dc_put_userptr(void *buf_priv)
> set_page_dirty_lock(pages[i]);
> sg_free_table(sgt);
> kfree(sgt);
> + } else {
> + dma_unmap_resource(buf->dev, buf->dma_addr, buf->size,
> + buf->dma_dir, 0);
> }
> vb2_destroy_framevec(buf->vec);
> kfree(buf);
> }
>
> -/*
> - * For some kind of reserved memory there might be no struct page available,
> - * so all that can be done to support such 'pages' is to try to convert
> - * pfn to dma address or at the last resort just assume that
> - * dma address == physical address (like it has been assumed in earlier version
> - * of videobuf2-dma-contig
> - */
> -
> -#ifdef __arch_pfn_to_dma
> -static inline dma_addr_t vb2_dc_pfn_to_dma(struct device *dev, unsigned long pfn)
> -{
> - return (dma_addr_t)__arch_pfn_to_dma(dev, pfn);
> -}
> -#elif defined(__pfn_to_bus)
> -static inline dma_addr_t vb2_dc_pfn_to_dma(struct device *dev, unsigned long pfn)
> -{
> - return (dma_addr_t)__pfn_to_bus(pfn);
> -}
> -#elif defined(__pfn_to_phys)
> -static inline dma_addr_t vb2_dc_pfn_to_dma(struct device *dev, unsigned long pfn)
> -{
> - return (dma_addr_t)__pfn_to_phys(pfn);
> -}
> -#else
> -static inline dma_addr_t vb2_dc_pfn_to_dma(struct device *dev, unsigned long pfn)
> -{
> - /* really, we cannot do anything better at this point */
> - return (dma_addr_t)(pfn) << PAGE_SHIFT;
> -}
> -#endif
> -
> static void *vb2_dc_get_userptr(struct device *dev, unsigned long vaddr,
> unsigned long size, enum dma_data_direction dma_dir)
> {
> @@ -528,7 +500,12 @@ static void *vb2_dc_get_userptr(struct device *dev, unsigned long vaddr,
> for (i = 1; i < n_pages; i++)
> if (nums[i-1] + 1 != nums[i])
> goto fail_pfnvec;
> - buf->dma_addr = vb2_dc_pfn_to_dma(buf->dev, nums[0]);
> + buf->dma_addr = dma_map_resource(buf->dev,
> + __pfn_to_phys(nums[0]), size, buf->dma_dir, 0);
> + if (dma_mapping_error(buf->dev, buf->dma_addr)) {
> + ret = -ENOMEM;
> + goto fail_pfnvec;
> + }
> goto out;
> }
>



Thanks,
Mauro

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