linux-kernel - Re: [PATCH RESEND 2/3] drivers/rtc/isl1208: Replace deprecated rtc_tm_to

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Date:	Mon, 01 Jun 2015 21:49:24 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Xunlei Pang <xlpang@....com>
Cc:	linux-kernel@...r.kernel.org, rtc-linux@...glegroups.com,
	Alessandro Zummo <a.zummo@...ertech.it>,
	John Stultz <john.stultz@...aro.org>,
	Xunlei Pang <pang.xunlei@...aro.org>,
	Herbert Valerio Riedel <hvr@....org>
Subject: Re: [PATCH RESEND 2/3] drivers/rtc/isl1208: Replace deprecated rtc_tm_to_time()

On Friday 29 May 2015 23:04:36 Xunlei Pang wrote:
> From: Xunlei Pang <pang.xunlei@...aro.org>
> 
> isl1208_i2c_set_alarm() uses deprecated rtc_tm_to_time(),
> which will overflow in year 2106 on 32-bit machines.
> 
> This patch solves this by:
>  - Replacing rtc_tm_to_time() with rtc_tm_to_time64()
> 
> Cc: Herbert Valerio Riedel <hvr@....org>
> Signed-off-by: Xunlei Pang <pang.xunlei@...aro.org>
> ---
>  drivers/rtc/rtc-isl1208.c | 11 ++++-------
>  1 file changed, 4 insertions(+), 7 deletions(-)

The patch looks correct, but I wonder if this is the best solution.
The only use of the two time values in the function is in the
'alarm_secs <= rtc_secs' comparison.

Maybe we should introduce an 'rtc_tm_before' helper function that
performs the same check? Do other drivers use the same piece
of code as this one?

	Arnd

> diff --git a/drivers/rtc/rtc-isl1208.c b/drivers/rtc/rtc-isl1208.c
> index c3c549d..06113e8 100644
> --- a/drivers/rtc/rtc-isl1208.c
> +++ b/drivers/rtc/rtc-isl1208.c
> @@ -370,19 +370,16 @@ isl1208_i2c_set_alarm(struct i2c_client *client, struct rtc_wkalrm *alarm)
>  	struct rtc_time *alarm_tm = &alarm->time;
>  	u8 regs[ISL1208_ALARM_SECTION_LEN] = { 0, };
>  	const int offs = ISL1208_REG_SCA;
> -	unsigned long rtc_secs, alarm_secs;
> +	time64_t rtc_secs, alarm_secs;
>  	struct rtc_time rtc_tm;
>  	int err, enable;
>  
>  	err = isl1208_i2c_read_time(client, &rtc_tm);
>  	if (err)
>  		return err;
> -	err = rtc_tm_to_time(&rtc_tm, &rtc_secs);
> -	if (err)
> -		return err;
> -	err = rtc_tm_to_time(alarm_tm, &alarm_secs);
> -	if (err)
> -		return err;
> +
> +	rtc_secs = rtc_tm_to_time64(&rtc_tm);
> +	alarm_secs = rtc_tm_to_time64(alarm_tm);
>  
>  	/* If the alarm time is before the current time disable the alarm */
>  	if (!alarm->enabled || alarm_secs <= rtc_secs)
> 

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