linux-kernel - Re: [PATCH] iio: adc: stmpe-adc: Shuffle an if statement around in stmpe_adc

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Message-ID: <CAKwvOdn4s_BdBPtOSyeQfRE+PCQLpDgm9VSkSR6eBkrBp_GhrA@mail.gmail.com>
Date:   Thu, 7 Mar 2019 10:31:55 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Nathan Chancellor <natechancellor@...il.com>
Cc:     Jonathan Cameron <jic23@...nel.org>,
        Lee Jones <lee.jones@...aro.org>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Stefan Agner <stefan@...er.ch>,
        Max Krummenacher <max.krummenacher@...adex.com>,
        Philippe Schenker <philippe.schenker@...adex.com>,
        linux-iio@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        clang-built-linux@...glegroups.com
Subject: Re: [PATCH] iio: adc: stmpe-adc: Shuffle an if statement around in stmpe_adc_isr

On Thu, Mar 7, 2019 at 9:16 AM Nathan Chancellor
<natechancellor@...il.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@...gle.com>
> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>

LGTM, thanks Nathan.
Reviewed-by: NIck Desaulniers <ndesaulniers@...gle.com>

> ---
>  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
>


-- 
Thanks,
~Nick Desaulniers