[ 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@xxxxxxxxx> Signed-off-by: Mark Brown <broonie@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- drivers/spi/spi.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index c2e85e23d538e..d74d341f9890d 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -955,6 +955,8 @@ static int spi_map_msg(struct spi_master *master, struct spi_message *msg) 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) -- 2.20.1