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rtc: pcf8523: refuse to write dates later than 2099

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When the chip increments the YEAR register and it already holds
bin2bcd(99) it reads as 0 afterwards. With this behaviour the last valid
day (without trickery) that has a representation is 2099-12-31 23:59:59.
So refuse to write later dates.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
This commit is contained in:
Uwe Kleine-König 2015-11-06 17:37:56 +01:00 committed by Alexandre Belloni
parent c60faa3afa
commit fbbf53f702
1 changed files with 11 additions and 0 deletions
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11
drivers/rtc/rtc-pcf8523.c
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@ -219,6 +219,17 @@ static int pcf8523_rtc_set_time(struct device *dev, struct rtc_time *tm)
u8 regs[8];
int err;
/*
* The hardware can only store values between 0 and 99 in it's YEAR
* register (with 99 overflowing to 0 on increment).
* After 2100-02-28 we could start interpreting the year to be in the
* interval [2100, 2199], but there is no path to switch in a smooth way
* because the chip handles YEAR=0x00 (and the out-of-spec
* YEAR=0xa0) as a leap year, but 2100 isn't.
*/
if (tm->tm_year < 100 || tm->tm_year >= 200)
return -EINVAL;
err = pcf8523_stop_rtc(client);
if (err < 0)
return err;