linux-kernel - [PATCH] It assume 20xx not 19xx.

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Message-Id: <20180531061351.6981-1-xiaolinkui@kylinos.cn>
Date:   Thu, 31 May 2018 14:13:51 +0800
From:   Linkui <xiaolinkui@...inos.cn>
To:     alexandre.belloni@...tlin.com
Cc:     linux-rtc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Linkui Xiao <xiaolinkui@...inos.cn>
Subject: [PATCH]  It assume 20xx not 19xx.

From: Linkui Xiao <xiaolinkui@...inos.cn>

If we settime between 1970 and 2000.
for example:
root# date 052915571978
root# hwclock -w

It will be wrong, this patch fix the bug.

Signed-off-by: Linkui Xiao <xiaolinkui@...inos.cn>
---
 drivers/rtc/rtc-ds1307.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
index a13e59e..8c218a1 100644
--- a/drivers/rtc/rtc-ds1307.c
+++ b/drivers/rtc/rtc-ds1307.c
@@ -425,7 +425,9 @@ static int ds1307_get_time(struct device *dev, struct rtc_time *t)
 	t->tm_mday = bcd2bin(regs[DS1307_REG_MDAY] & 0x3f);
 	tmp = regs[DS1307_REG_MONTH] & 0x1f;
 	t->tm_mon = bcd2bin(tmp) - 1;
-	t->tm_year = bcd2bin(regs[DS1307_REG_YEAR]) + 100;
+	t->tm_year = bcd2bin(regs[DS1307_REG_YEAR]);
+	if (t->tm_year >= 0 && t->tm_year <= 69)
+		t->tm_year += 100;
 
 	if (regs[chip->century_reg] & chip->century_bit &&
 	    IS_ENABLED(CONFIG_RTC_DRV_DS1307_CENTURY))
@@ -454,7 +456,7 @@ static int ds1307_set_time(struct device *dev, struct rtc_time *t)
 		t->tm_hour, t->tm_mday,
 		t->tm_mon, t->tm_year, t->tm_wday);
 
-	if (t->tm_year < 100)
+	if (t->tm_year < 0)
 		return -EINVAL;
 
 #ifdef CONFIG_RTC_DRV_DS1307_CENTURY
@@ -472,8 +474,9 @@ static int ds1307_set_time(struct device *dev, struct rtc_time *t)
 	regs[DS1307_REG_MDAY] = bin2bcd(t->tm_mday);
 	regs[DS1307_REG_MONTH] = bin2bcd(t->tm_mon + 1);
 
-	/* assume 20YY not 19YY */
-	tmp = t->tm_year - 100;
+	tmp = t->tm_year;
+	if (tmp >= 100 && tmp <= 169)
+		tmp -= 100;
 	regs[DS1307_REG_YEAR] = bin2bcd(tmp);
 
 	if (chip->century_enable_bit)
-- 
2.7.4