linux-kernel - Re: [PATCH] rtc: report time-retrieval errors when updating alarm

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Date:   Mon, 21 Oct 2019 18:11:13 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Brian Norris <briannorris@...omium.org>
Cc:     Alessandro Zummo <a.zummo@...ertech.it>, linux-rtc@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Jeffy Chen <jeffy.chen@...k-chips.com>,
        Matthias Kaehlcke <mka@...omium.org>
Subject: Re: [PATCH] rtc: report time-retrieval errors when updating alarm

Hello Brian,

On 21/05/2018 09:42:22-0700, Brian Norris wrote:
> __rtc_read_time() can fail (e.g., if the RTC uses an unreliable medium).
> When it does, we don't report the error, but instead calculate a
> 1-second alarm based on the potentially-garbage 'tm' (in practice,
> __rtc_read_time() zeroes out the time first, so it's likely to still be
> all 0).
> 
> Let's propagate the error instead.
> 

I submitted
https://lore.kernel.org/linux-rtc/20191021155631.3342-2-alexandre.belloni@bootlin.com/T/#u
to solve this after looking at all the implication checking the return
value of __rtc_read_time had.

> Signed-off-by: Brian Norris <briannorris@...omium.org>
> ---
>  drivers/rtc/interface.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c
> index 7cbdc9228dd5..a4bdd8b5fe2e 100644
> --- a/drivers/rtc/interface.c
> +++ b/drivers/rtc/interface.c
> @@ -555,7 +555,9 @@ int rtc_update_irq_enable(struct rtc_device *rtc, unsigned int enabled)
>  		struct rtc_time tm;
>  		ktime_t now, onesec;
>  
> -		__rtc_read_time(rtc, &tm);
> +		err = __rtc_read_time(rtc, &tm);
> +		if (err)
> +			goto out;
>  		onesec = ktime_set(1, 0);
>  		now = rtc_tm_to_ktime(tm);
>  		rtc->uie_rtctimer.node.expires = ktime_add(now, onesec);
> -- 
> 2.17.0.441.gb46fe60e1d-goog
> 

-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com