queue-4.4/spi-fix-zero-length-xfer-bug.patch

   1 From 10de7ce50a7f99f93255fb576dc49fd914ae33ec Mon Sep 17 00:00:00 2001
   2 From: Chris Lesiak <chris.lesiak@licor.com>
   3 Date: Thu, 7 Mar 2019 20:39:00 +0000
   4 Subject: spi: Fix zero length xfer bug
   5
   6 [ Upstream commit 5442dcaa0d90fc376bdfc179a018931a8f43dea4 ]
   7
   8 This fixes a bug for messages containing both zero length and
   9 unidirectional xfers.
  10
  11 The function spi_map_msg will allocate dummy tx and/or rx buffers
  12 for use with unidirectional transfers when the hardware can only do
  13 a bidirectional transfer.  That dummy buffer will be used in place
  14 of a NULL buffer even when the xfer length is 0.
  15
  16 Then in the function __spi_map_msg, if he hardware can dma,
  17 the zero length xfer will have spi_map_buf called on the dummy
  18 buffer.
  19
  20 Eventually, __sg_alloc_table is called and returns -EINVAL
  21 because nents == 0.
  22
  23 This fix prevents the error by not using the dummy buffer when
  24 the xfer length is zero.
  25
  26 Signed-off-by: Chris Lesiak <chris.lesiak@licor.com>
  27 Signed-off-by: Mark Brown <broonie@kernel.org>
  28 Signed-off-by: Sasha Levin <sashal@kernel.org>
  29 ---
  30  drivers/spi/spi.c | 2 ++
  31  1 file changed, 2 insertions(+)
  32
  33 diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
  34 index 04fd651f9e3e3..c132c676df3a6 100644
  35 --- a/drivers/spi/spi.c
  36 +++ b/drivers/spi/spi.c
  37 @@ -903,6 +903,8 @@ static int spi_map_msg(struct spi_master *master, struct spi_message *msg)
  38                 if (max_tx || max_rx) {
  39                         list_for_each_entry(xfer, &msg->transfers,
  40                                             transfer_list) {
  41 +                               if (!xfer->len)
  42 +                                       continue;
  43                                 if (!xfer->tx_buf)
  44                                         xfer->tx_buf = master->dummy_tx;
  45                                 if (!xfer->rx_buf)
  46 --
  47 2.20.1
  48