spi: Fix zero length xfer bug
[ Upstream commit 5442dcaa0d90fc376bdfc179a018931a8f43dea4 ]
This fixes a bug for messages containing both zero length and
unidirectional xfers.
The function spi_map_msg will allocate dummy tx and/or rx buffers
for use with unidirectional transfers when the hardware can only do
a bidirectional transfer. That dummy buffer will be used in place
of a NULL buffer even when the xfer length is 0.
Then in the function __spi_map_msg, if he hardware can dma,
the zero length xfer will have spi_map_buf called on the dummy
buffer.
Eventually, __sg_alloc_table is called and returns -EINVAL
because nents == 0.
This fix prevents the error by not using the dummy buffer when
the xfer length is zero.
Signed-off-by: Chris Lesiak <chris.lesiak@licor.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index c2e85e2..d74d341 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -955,6 +955,8 @@
if (max_tx || max_rx) {
list_for_each_entry(xfer, &msg->transfers,
transfer_list) {
+ if (!xfer->len)
+ continue;
if (!xfer->tx_buf)
xfer->tx_buf = master->dummy_tx;
if (!xfer->rx_buf)