From 5442dcaa0d90fc376bdfc179a018931a8f43dea4 Mon Sep 17 00:00:00 2001
From: Chris Lesiak <chris.lesiak@licor.com>
Date: Thu, 7 Mar 2019 20:39:00 +0000
Subject: [PATCH] spi: Fix zero length xfer bug
Git-commit: 5442dcaa0d90fc376bdfc179a018931a8f43dea4
Patch-mainline: v5.2-rc1
References: bsc#1051510
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>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/spi/spi.c | 2 ++
1 file changed, 2 insertions(+)
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -988,6 +988,8 @@ static int spi_map_msg(struct spi_master
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)