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author | Marek Szyprowski <m.szyprowski@samsung.com> | 2020-05-08 16:07:13 +0200 |
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committer | Marek Szyprowski <m.szyprowski@samsung.com> | 2020-09-10 08:18:35 +0200 |
commit | d1749eb1ab85e04e58c29e58900e3abebbdd6e82 (patch) | |
tree | 7b64d67a2c7b854a08467131d1a7e16566f1c484 /drivers/gpu/host1x/job.c | |
parent | 5e0ff16b9edf3379e5a0e1545b0d9831a7353cca (diff) |
xen: gntdev: fix common struct sg_table related issues
The Documentation/DMA-API-HOWTO.txt states that the dma_map_sg() function
returns the number of the created entries in the DMA address space.
However the subsequent calls to the dma_sync_sg_for_{device,cpu}() and
dma_unmap_sg must be called with the original number of the entries
passed to the dma_map_sg().
struct sg_table is a common structure used for describing a non-contiguous
memory buffer, used commonly in the DRM and graphics subsystems. It
consists of a scatterlist with memory pages and DMA addresses (sgl entry),
as well as the number of scatterlist entries: CPU pages (orig_nents entry)
and DMA mapped pages (nents entry).
It turned out that it was a common mistake to misuse nents and orig_nents
entries, calling DMA-mapping functions with a wrong number of entries or
ignoring the number of mapped entries returned by the dma_map_sg()
function.
To avoid such issues, lets use a common dma-mapping wrappers operating
directly on the struct sg_table objects and use scatterlist page
iterators where possible. This, almost always, hides references to the
nents and orig_nents entries, making the code robust, easier to follow
and copy/paste safe.
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Juergen Gross <jgross@suse.com>
Diffstat (limited to 'drivers/gpu/host1x/job.c')
0 files changed, 0 insertions, 0 deletions