linux-kernel - Re: [PATCH v2 1/2] rtc: wilco-ec: Remove yday and wday calculations

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Message-ID: <20190922161306.GA1999@bug>
Date:   Sun, 22 Sep 2019 18:13:06 +0200
From:   Pavel Machek <pavel@....cz>
To:     Nick Crews <ncrews@...omium.org>
Cc:     bleung@...omium.org,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        enric.balletbo@...labora.com, linux-kernel@...r.kernel.org,
        dlaurie@...omium.org
Subject: Re: [PATCH v2 1/2] rtc: wilco-ec: Remove yday and wday calculations

On Mon 2019-09-16 12:12:15, Nick Crews wrote:
> The tm_yday and tm_wday fields are not used by userspace,
> so since they aren't needed within the driver, don't
> bother calculating them. This is especially needed since
> the rtc_year_days() call was crashing if the HW returned
> an invalid time.
> 
> Signed-off-by: Nick Crews <ncrews@...omium.org>
> ---
>  drivers/rtc/rtc-wilco-ec.c | 4 ----
>  1 file changed, 4 deletions(-)
> 
> diff --git a/drivers/rtc/rtc-wilco-ec.c b/drivers/rtc/rtc-wilco-ec.c
> index 8ad4c4e6d557..e84faa268caf 100644
> --- a/drivers/rtc/rtc-wilco-ec.c
> +++ b/drivers/rtc/rtc-wilco-ec.c
> @@ -110,10 +110,6 @@ static int wilco_ec_rtc_read(struct device *dev, struct rtc_time *tm)
>  	tm->tm_mday	= rtc.day;
>  	tm->tm_mon	= rtc.month - 1;
>  	tm->tm_year	= rtc.year + (rtc.century * 100) - 1900;
> -	tm->tm_yday	= rtc_year_days(tm->tm_mday, tm->tm_mon, tm->tm_year);
> -
> -	/* Don't compute day of week, we don't need it. */
> -	tm->tm_wday = -1;
>  
>  	return 0;

Are you sure? It would be bad to pass unititialized memory to userspace...

If userspace does not need those fields, why are they there?

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html