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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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