linux-kernel - [PATCH 1/2] spi: qup: hide warning for uninitialized variable

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Date:   Thu, 10 Aug 2017 14:13:26 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        Mark Brown <broonie@...nel.org>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Varadarajan Narayanan <varada@...eaurora.org>,
        Matthew McClintock <mmcclint@...eaurora.org>,
        Sudeep Holla <sudeep.holla@....com>,
        linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org,
        linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] spi: qup: hide warning for uninitialized variable

The added conditionals in this function apparently confused
gcc to the point that it no longer sees the code is safe and
instead shows a false-positive warning:

drivers/spi/spi-qup.c: In function 'spi_qup_transfer_one':
drivers/spi/spi-qup.c:507:28: error: 'tx_nents' may be used uninitialized in this function [-Werror=maybe-uninitialized]
drivers/spi/spi-qup.c:464:17: note: 'tx_nents' was declared here
drivers/spi/spi-qup.c:505:28: error: 'rx_nents' may be used uninitialized in this function [-Werror=maybe-uninitialized]
drivers/spi/spi-qup.c:464:7: note: 'rx_nents' was declared here

This moves the initialization to a place that makes it obvious
to the compiler.

Fixes: 5884e17ef3cb ("spi: qup: allow multiple DMA transactions per spi xfer")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/spi/spi-qup.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/spi/spi-qup.c b/drivers/spi/spi-qup.c
index 1364516e87c2..e9ecd67cd817 100644
--- a/drivers/spi/spi-qup.c
+++ b/drivers/spi/spi-qup.c
@@ -427,8 +427,6 @@ static u32 spi_qup_sgl_get_nents_len(struct scatterlist *sgl, u32 max,
 	struct scatterlist *sg;
 	u32 total = 0;
 
-	*nents = 0;
-
 	for (sg = sgl; sg; sg = sg_next(sg)) {
 		unsigned int len = sg_dma_len(sg);
 
@@ -461,7 +459,7 @@ static int spi_qup_do_dma(struct spi_device *spi, struct spi_transfer *xfer,
 	tx_sgl = xfer->tx_sg.sgl;
 
 	do {
-		u32 rx_nents, tx_nents;
+		u32 rx_nents = 0, tx_nents = 0;
 
 		if (rx_sgl)
 			qup->n_words = spi_qup_sgl_get_nents_len(rx_sgl,
-- 
2.9.0