linux-kernel - Re: [PATCH] rtc: zynqmp: initialize fract

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Date:   Fri, 5 Aug 2022 10:04:02 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     alexandre.belloni@...tlin.com
Cc:     Alessandro Zummo <a.zummo@...ertech.it>,
        Michal Simek <michal.simek@...inx.com>,
        linux-rtc@...r.kernel.org, kernel test robot <lkp@...el.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev
Subject: Re: [PATCH] rtc: zynqmp: initialize fract_tick

On Wed, Jul 27, 2022 at 12:00:18PM +0200, alexandre.belloni@...tlin.com wrote:
> From: Alexandre Belloni <alexandre.belloni@...tlin.com>
> 
> fract_tick is used uninitialized when fract_offset is 0
> 
> Reported-by: kernel test robot <lkp@...el.com>
> Signed-off-by: Alexandre Belloni <alexandre.belloni@...tlin.com>

Reviewed-by: Nathan Chancellor <nathan@...nel.org>

Is this going to be applied soon? This is one of the warnings breaking
allmodconfig with clang right now:

    drivers/rtc/rtc-zynqmp.c:223:7: error: variable 'fract_tick' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
                    if (fract_offset > (tick_mult / RTC_FR_MAX_TICKS)) {
                        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    drivers/rtc/rtc-zynqmp.c:238:6: note: uninitialized use occurs here
            if (fract_tick)
                ^~~~~~~~~~
    drivers/rtc/rtc-zynqmp.c:223:3: note: remove the 'if' if its condition is always true
                    if (fract_offset > (tick_mult / RTC_FR_MAX_TICKS)) {
                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    drivers/rtc/rtc-zynqmp.c:218:6: error: variable 'fract_tick' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
            if (fract_offset) {
                ^~~~~~~~~~~~
    drivers/rtc/rtc-zynqmp.c:238:6: note: uninitialized use occurs here
            if (fract_tick)
                ^~~~~~~~~~
    drivers/rtc/rtc-zynqmp.c:218:2: note: remove the 'if' if its condition is always true
            if (fract_offset) {
            ^~~~~~~~~~~~~~~~~~
    drivers/rtc/rtc-zynqmp.c:206:26: note: initialize the variable 'fract_tick' to silence this warning
            unsigned char fract_tick;
                                    ^
                                    = '\0'
    2 errors generated.

> ---
>  drivers/rtc/rtc-zynqmp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/rtc/rtc-zynqmp.c b/drivers/rtc/rtc-zynqmp.c
> index 1dd389b891fe..c9b85c838ebe 100644
> --- a/drivers/rtc/rtc-zynqmp.c
> +++ b/drivers/rtc/rtc-zynqmp.c
> @@ -203,7 +203,7 @@ static int xlnx_rtc_set_offset(struct device *dev, long offset)
>  	struct xlnx_rtc_dev *xrtcdev = dev_get_drvdata(dev);
>  	unsigned long long rtc_ppb = RTC_PPB;
>  	unsigned int tick_mult = do_div(rtc_ppb, xrtcdev->freq);
> -	unsigned char fract_tick;
> +	unsigned char fract_tick = 0;
>  	unsigned int calibval;
>  	short int  max_tick;
>  	int fract_offset;
> -- 
> 2.36.1
> 
>