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spi: Fix scatterlist elements size in spi_map_buf
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commit ce99319 upstream.

When SPI transfers can be offloaded using DMA, the SPI core need to
build a scatterlist to make sure that the buffer to be transferred is
dma-able.

This patch fixes the scatterlist entry size computation in the case
where the maximum acceptable scatterlist entry supported by the DMA
controller is less than PAGE_SIZE, when the buffer is vmalloced.

For each entry, the actual size is given by the minimum between the
desc_len (which is the max buffer size supported by the DMA controller)
and the remaining buffer length until we cross a page boundary.

Fixes: 65598c1 ("spi: Fix per-page mapping of unaligned vmalloc-ed buffer")
Signed-off-by: Maxime Chevallier <[email protected]>
Signed-off-by: Mark Brown <[email protected]>
Cc: [email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>
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minimaxwell authored and gregkh committed Apr 24, 2018
1 parent faddb17 commit e4ff723
Showing 1 changed file with 8 additions and 2 deletions.
10 changes: 8 additions & 2 deletions drivers/spi/spi.c
Original file line number Diff line number Diff line change
Expand Up @@ -779,8 +779,14 @@ static int spi_map_buf(struct spi_controller *ctlr, struct device *dev,
for (i = 0; i < sgs; i++) {

if (vmalloced_buf || kmap_buf) {
min = min_t(size_t,
len, desc_len - offset_in_page(buf));
/*
* Next scatterlist entry size is the minimum between
* the desc_len and the remaining buffer length that
* fits in a page.
*/
min = min_t(size_t, desc_len,
min_t(size_t, len,
PAGE_SIZE - offset_in_page(buf)));
if (vmalloced_buf)
vm_page = vmalloc_to_page(buf);
else
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