Re: [PATCH] iio: adc: stmpe-adc: Shuffle an if statement around in stmpe_adc_isr

From: Jonathan Cameron <jic23@kernel.org>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: Nathan Chancellor <natechancellor@gmail.com>,
	Lee Jones <lee.jones@linaro.org>,
	Hartmut Knaack <knaack.h@gmx.de>,
	Lars-Peter Clausen <lars@metafoo.de>,
	Peter Meerwald-Stadler <pmeerw@pmeerw.net>,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	Alexandre Torgue <alexandre.torgue@st.com>,
	Stefan Agner <stefan@agner.ch>,
	Max Krummenacher <max.krummenacher@toradex.com>,
	Philippe Schenker <philippe.schenker@toradex.com>,
	linux-iio@vger.kernel.org,
	linux-stm32@st-md-mailman.stormreply.com,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	LKML <linux-kernel@vger.kernel.org>,
	clang-built-linux@googlegroups.com
Subject: Re: [PATCH] iio: adc: stmpe-adc: Shuffle an if statement around in stmpe_adc_isr
Date: Sun, 10 Mar 2019 09:45:56 +0000	[thread overview]
Message-ID: <20190310094556.3ae7c5fa@archlinux> (raw)
In-Reply-To: <CAKwvOdn4s_BdBPtOSyeQfRE+PCQLpDgm9VSkSR6eBkrBp_GhrA@mail.gmail.com>

On Thu, 7 Mar 2019 10:31:55 -0800
Nick Desaulniers <ndesaulniers@google.com> wrote:

> On Thu, Mar 7, 2019 at 9:16 AM Nathan Chancellor
> <natechancellor@gmail.com> wrote:
> >
> > When building with -Wsometimes-uninitialized, Clang warns:
> >
> > drivers/iio/adc/stmpe-adc.c:204:13: warning: variable 'data' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
> >
> > Clang can't tell that data will never be used uninitialized because the
> > two if statements take care of all cases. Remove the first if statement
> > and make it the else branch of the second one so that it is apparent to
> > Clang that all cases are covered.
> >
> > Link: https://github.com/ClangBuiltLinux/linux/issues/387
> > Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
> > Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>  
> 
> LGTM, thanks Nathan.
> Reviewed-by: NIck Desaulniers <ndesaulniers@google.com>
Agreed. Seems obviously correct.  Stefan, I'm only pushing this out as
testing for now so happy to rebase if you have comments.

Thanks,

Jonathan

> 
> > ---
> >  drivers/iio/adc/stmpe-adc.c | 5 ++---
> >  1 file changed, 2 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/iio/adc/stmpe-adc.c b/drivers/iio/adc/stmpe-adc.c
> > index 37f4b74a5d32..7921f827c6ec 100644
> > --- a/drivers/iio/adc/stmpe-adc.c
> > +++ b/drivers/iio/adc/stmpe-adc.c
> > @@ -184,9 +184,6 @@ static irqreturn_t stmpe_adc_isr(int irq, void *dev_id)
> >         struct stmpe_adc *info = (struct stmpe_adc *)dev_id;
> >         u16 data;
> >
> > -       if (info->channel > STMPE_TEMP_CHANNEL)
> > -               return IRQ_NONE;
> > -
> >         if (info->channel <= STMPE_ADC_LAST_NR) {
> >                 int int_sta;
> >
> > @@ -205,6 +202,8 @@ static irqreturn_t stmpe_adc_isr(int irq, void *dev_id)
> >                 /* Read value */
> >                 stmpe_block_read(info->stmpe, STMPE_REG_TEMP_DATA, 2,
> >                                 (u8 *) &data);
> > +       } else {
> > +               return IRQ_NONE;
> >         }
> >
> >         info->value = (u32) be16_to_cpu(data);
> > --
> > 2.21.0
> >  
> 
>