linux-kernel - Re: [PATCH] rtc: rzn1: initialize val in rzn1_rtc_set

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Date:   Wed, 18 May 2022 17:09:20 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Tom Rix <trix@...hat.com>
Cc:     a.zummo@...ertech.it, alexandre.belloni@...tlin.com,
        nathan@...nel.org, ndesaulniers@...gle.com,
        linux-rtc@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH] rtc: rzn1: initialize val in rzn1_rtc_set_offset

Hi,

trix@...hat.com wrote on Wed, 18 May 2022 09:47:47 -0400:

> The clang build fails with
> rtc-rzn1.c:291:3: error: variable 'val' is uninitialized when used here [-Werror,-Wuninitialized]
>   val |= RZN1_RTC_SUBU_DEV;
>   ^~~
> 
> The val variable in rzn1_rtc_set_offset() is never initialized so
> the series of |= operations in the function will start with a
> garbage value.  So initialize val to 0.
> 
> Fixes: be4a11cf98af ("rtc: rzn1: Add oscillator offset support")
> Signed-off-by: Tom Rix <trix@...hat.com>
> ---
>  drivers/rtc/rtc-rzn1.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/rtc/rtc-rzn1.c b/drivers/rtc/rtc-rzn1.c
> index 980ade8c9601..0b4bf6e43464 100644
> --- a/drivers/rtc/rtc-rzn1.c
> +++ b/drivers/rtc/rtc-rzn1.c
> @@ -272,7 +272,7 @@ static int rzn1_rtc_set_offset(struct device *dev, long offset)
>  	struct rzn1_rtc *rtc = dev_get_drvdata(dev);
>  	unsigned int steps;
>  	int stepsh, stepsl;
> -	u32 val;
> +	u32 val = 0;

Actually reviewing this makes me realize I mixed two variables
together:
- val here and below should be renamed to something like "subu" or
  and indeed initialized to 0 here.
- a "ctl2" u32 should be introduced and be used instead of "val" in the
  readl_poll_timeout() call.

Thanks,
Miquèl