From fbbf53f70225c82ba877de780486be5bc81b29e2 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= Date: Fri, 6 Nov 2015 17:37:56 +0100 Subject: [PATCH] rtc: pcf8523: refuse to write dates later than 2099 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Signed-off-by: Alexandre Belloni --- drivers/rtc/rtc-pcf8523.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/drivers/rtc/rtc-pcf8523.c b/drivers/rtc/rtc-pcf8523.c index e7ebcc0b7e59..988566caaaa6 100644 --- a/drivers/rtc/rtc-pcf8523.c +++ b/drivers/rtc/rtc-pcf8523.c @@ -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;