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dma-buf: Clarify that dma-buf sg lists are page aligned

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The dma-buf API have been used under the assumption that the sg lists
returned from dma_buf_map_attachment() are fully page aligned. Lots of
stuff can break otherwise all over the place. Clarify this in the
documentation and add a check when DMA API debug is enabled.

Signed-off-by: Jianxin Xiong <jianxin.xiong@intel.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/1602692161-107096-1-git-send-email-jianxin.xiong@intel.com
This commit is contained in:
Jianxin Xiong 2020-10-14 09:16:01 -07:00 committed by Daniel Vetter
parent 73b62cdb93
commit ac80cd17a6
2 changed files with 23 additions and 1 deletions
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21
drivers/dma-buf/dma-buf.c
View File

@ -849,6 +849,9 @@ EXPORT_SYMBOL_GPL(dma_buf_unpin);
* Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
* on error. May return -EINTR if it is interrupted by a signal.
*
* On success, the DMA addresses and lengths in the returned scatterlist are
* PAGE_SIZE aligned.
*
* A mapping must be unmapped by using dma_buf_unmap_attachment(). Note that
* the underlying backing storage is pinned for as long as a mapping exists,
* therefore users/importers should not hold onto a mapping for undue amounts of
@ -902,6 +905,24 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
attach->dir = direction;
}
#ifdef CONFIG_DMA_API_DEBUG
{
struct scatterlist *sg;
u64 addr;
int len;
int i;
for_each_sgtable_dma_sg(sg_table, sg, i) {
addr = sg_dma_address(sg);
len = sg_dma_len(sg);
if (!PAGE_ALIGNED(addr) || !PAGE_ALIGNED(len)) {
pr_debug("%s: addr %llx or len %x is not page aligned!\n",
__func__, addr, len);
}
}
}
#endif /* CONFIG_DMA_API_DEBUG */
return sg_table;
}
EXPORT_SYMBOL_GPL(dma_buf_map_attachment);

3
include/linux/dma-buf.h
View File

@ -146,7 +146,8 @@ struct dma_buf_ops {
*
* A &sg_table scatter list of or the backing storage of the DMA buffer,
* already mapped into the device address space of the &device attached
* with the provided &dma_buf_attachment.
* with the provided &dma_buf_attachment. The addresses and lengths in
* the scatter list are PAGE_SIZE aligned.
*
* On failure, returns a negative error value wrapped into a pointer.
* May also return -EINTR when a signal was received while being