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.xi...@intel.com>
---
drivers/dma-buf/dma-buf.c | 21 +++++++++++++++++++++
include/linux/dma-buf.h | 3 ++-
2 files changed, 23 insertions(+), 1 deletion(-)
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 844967f..7309c83 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -851,6 +851,9 @@ void dma_buf_unpin(struct dma_buf_attachment *attach)
* 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
@@ -904,6 +907,24 @@ 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);
diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
index a2ca294e..4a5fa70 100644
--- a/include/linux/dma-buf.h
+++ b/include/linux/dma-buf.h
@@ -145,7 +145,8 @@ 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
--
1.8.3.1
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