From: Arnd Bergmann <arnd@arndb.de> To: Mark Brown <broonie@kernel.org> Cc: Addy Ke <addy.ke@rock-chips.com>, Doug Anderson <dianders@chromium.org>, linux-arm-kernel@lists.infradead.org, linux-spi@vger.kernel.org Subject: [PATCH] spi/rockchip: avoid uninitialized-use warning Date: Wed, 28 Jan 2015 14:25:10 +0100 [thread overview] Message-ID: <1957186.KORYFIrP42@wuerfel> (raw) We currently get a warning about potentially uninitialized variables in the rockchip spi driver, at least in certain toolchain versions: spi/spi-rockchip.c: In function 'rockchip_spi_prepare_dma': include/linux/dmaengine.h:796:2: warning: 'txdesc' may be used uninitialized in this function include/linux/dmaengine.h:796:2: warning: 'rxdesc' may be used uninitialized in this function The reason seems to be that gcc cannot know whether the value of the rs->rx and rs->tx variables change between the two points these are accessed. The code is actually correct, but to make this clearer to the compiler, this changes the conditionals to test for the local rxdesc/txdesc variables instead, which it knows won't change. Signed-off-by: Arnd Bergmann <arnd@arndb.de> diff --git a/drivers/spi/spi-rockchip.c b/drivers/spi/spi-rockchip.c index daabbabd26b0..1a777dc261d6 100644 --- a/drivers/spi/spi-rockchip.c +++ b/drivers/spi/spi-rockchip.c @@ -437,6 +437,7 @@ static void rockchip_spi_prepare_dma(struct rockchip_spi *rs) rs->state &= ~TXBUSY; spin_unlock_irqrestore(&rs->lock, flags); + rxdesc = NULL; if (rs->rx) { rxconf.direction = rs->dma_rx.direction; rxconf.src_addr = rs->dma_rx.addr; @@ -453,6 +454,7 @@ static void rockchip_spi_prepare_dma(struct rockchip_spi *rs) rxdesc->callback_param = rs; } + txdesc = NULL; if (rs->tx) { txconf.direction = rs->dma_tx.direction; txconf.dst_addr = rs->dma_tx.addr; @@ -470,7 +472,7 @@ static void rockchip_spi_prepare_dma(struct rockchip_spi *rs) } /* rx must be started before tx due to spi instinct */ - if (rs->rx) { + if (rxdesc) { spin_lock_irqsave(&rs->lock, flags); rs->state |= RXBUSY; spin_unlock_irqrestore(&rs->lock, flags); @@ -478,7 +480,7 @@ static void rockchip_spi_prepare_dma(struct rockchip_spi *rs) dma_async_issue_pending(rs->dma_rx.ch); } - if (rs->tx) { + if (txdesc) { spin_lock_irqsave(&rs->lock, flags); rs->state |= TXBUSY; spin_unlock_irqrestore(&rs->lock, flags);
WARNING: multiple messages have this Message-ID (diff)
From: arnd@arndb.de (Arnd Bergmann) To: linux-arm-kernel@lists.infradead.org Subject: [PATCH] spi/rockchip: avoid uninitialized-use warning Date: Wed, 28 Jan 2015 14:25:10 +0100 [thread overview] Message-ID: <1957186.KORYFIrP42@wuerfel> (raw) We currently get a warning about potentially uninitialized variables in the rockchip spi driver, at least in certain toolchain versions: spi/spi-rockchip.c: In function 'rockchip_spi_prepare_dma': include/linux/dmaengine.h:796:2: warning: 'txdesc' may be used uninitialized in this function include/linux/dmaengine.h:796:2: warning: 'rxdesc' may be used uninitialized in this function The reason seems to be that gcc cannot know whether the value of the rs->rx and rs->tx variables change between the two points these are accessed. The code is actually correct, but to make this clearer to the compiler, this changes the conditionals to test for the local rxdesc/txdesc variables instead, which it knows won't change. Signed-off-by: Arnd Bergmann <arnd@arndb.de> diff --git a/drivers/spi/spi-rockchip.c b/drivers/spi/spi-rockchip.c index daabbabd26b0..1a777dc261d6 100644 --- a/drivers/spi/spi-rockchip.c +++ b/drivers/spi/spi-rockchip.c @@ -437,6 +437,7 @@ static void rockchip_spi_prepare_dma(struct rockchip_spi *rs) rs->state &= ~TXBUSY; spin_unlock_irqrestore(&rs->lock, flags); + rxdesc = NULL; if (rs->rx) { rxconf.direction = rs->dma_rx.direction; rxconf.src_addr = rs->dma_rx.addr; @@ -453,6 +454,7 @@ static void rockchip_spi_prepare_dma(struct rockchip_spi *rs) rxdesc->callback_param = rs; } + txdesc = NULL; if (rs->tx) { txconf.direction = rs->dma_tx.direction; txconf.dst_addr = rs->dma_tx.addr; @@ -470,7 +472,7 @@ static void rockchip_spi_prepare_dma(struct rockchip_spi *rs) } /* rx must be started before tx due to spi instinct */ - if (rs->rx) { + if (rxdesc) { spin_lock_irqsave(&rs->lock, flags); rs->state |= RXBUSY; spin_unlock_irqrestore(&rs->lock, flags); @@ -478,7 +480,7 @@ static void rockchip_spi_prepare_dma(struct rockchip_spi *rs) dma_async_issue_pending(rs->dma_rx.ch); } - if (rs->tx) { + if (txdesc) { spin_lock_irqsave(&rs->lock, flags); rs->state |= TXBUSY; spin_unlock_irqrestore(&rs->lock, flags);
next reply other threads:[~2015-01-28 13:25 UTC|newest] Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top 2015-01-28 13:25 Arnd Bergmann [this message] 2015-01-28 13:25 ` [PATCH] spi/rockchip: avoid uninitialized-use warning Arnd Bergmann 2015-01-28 13:27 ` [PATCH] spi: pl08x: do not select S3C64XX_PL080 Arnd Bergmann 2015-01-28 13:27 ` Arnd Bergmann 2015-01-28 17:37 ` Mark Brown 2015-01-28 17:37 ` Mark Brown 2015-01-28 17:36 ` [PATCH] spi/rockchip: avoid uninitialized-use warning Mark Brown 2015-01-28 17:36 ` Mark Brown
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