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Message-ID: <20110826102846.17135.516.stgit@localhost.localdomain>
Date: Fri, 26 Aug 2011 11:30:04 +0100
From: Alan Cox <alan@...rguk.ukuu.org.uk>
To: x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] vrtc: change its year offset from 1960 to 1972
From: Feng Tang <feng.tang@...el.com>
Real world year equals the value in vrtc YEAR register plus an offset.
We used 1960 for original developepment as the offset to make leap year
consistent, but for a device's first use, its YEAR register is 0 and the
system year will be parsed as 1960 which is not a valid UNIX time and will
cause many applications to fail mysteriously. Devices use 1972 instead to
fix this issue.
Updated patch which adds a sanity check suggested by Mathias
Signed-off-by: Feng Tang <feng.tang@...el.com>
Signed-off-by: Alan Cox <alan@...ux.intel.com>
---
arch/x86/platform/mrst/vrtc.c | 4 ++--
drivers/rtc/rtc-mrst.c | 19 +++++++++++--------
2 files changed, 13 insertions(+), 10 deletions(-)
diff --git a/arch/x86/platform/mrst/vrtc.c b/arch/x86/platform/mrst/vrtc.c
index 901e622..8efb035 100644
--- a/arch/x86/platform/mrst/vrtc.c
+++ b/arch/x86/platform/mrst/vrtc.c
@@ -71,8 +71,8 @@ unsigned long vrtc_get_time(void)
mon = vrtc_cmos_read(RTC_MONTH);
year = vrtc_cmos_read(RTC_YEAR);
- /* vRTC YEAR reg contains the offset to 1960 */
- year += 1960;
+ /* vRTC YEAR reg contains the offset to 1972 */
+ year += 1972;
printk(KERN_INFO "vRTC: sec: %d min: %d hour: %d day: %d "
"mon: %d year: %d\n", sec, min, hour, mday, mon, year);
diff --git a/drivers/rtc/rtc-mrst.c b/drivers/rtc/rtc-mrst.c
index d335448..bb21f44 100644
--- a/drivers/rtc/rtc-mrst.c
+++ b/drivers/rtc/rtc-mrst.c
@@ -76,12 +76,15 @@ static inline unsigned char vrtc_is_updating(void)
/*
* rtc_time's year contains the increment over 1900, but vRTC's YEAR
* register can't be programmed to value larger than 0x64, so vRTC
- * driver chose to use 1960 (1970 is UNIX time start point) as the base,
+ * driver chose to use 1972 (1970 is UNIX time start point) as the base,
* and does the translation at read/write time.
*
- * Why not just use 1970 as the offset? it's because using 1960 will
+ * Why not just use 1970 as the offset? it's because using 1972 will
* make it consistent in leap year setting for both vrtc and low-level
- * physical rtc devices.
+ * physical rtc devices. Then why not use 1960 as the offset? If we use
+ * 1960, for a device's first use, its YEAR register is 0 and the system
+ * year will be parsed as 1960 which is not a valid UNIX time and will
+ * cause many applications to fail mysteriously.
*/
static int mrst_read_time(struct device *dev, struct rtc_time *time)
{
@@ -99,10 +102,10 @@ static int mrst_read_time(struct device *dev, struct rtc_time *time)
time->tm_year = vrtc_cmos_read(RTC_YEAR);
spin_unlock_irqrestore(&rtc_lock, flags);
- /* Adjust for the 1960/1900 */
- time->tm_year += 60;
+ /* Adjust for the 1972/1900 */
+ time->tm_year += 72;
time->tm_mon--;
- return RTC_24H;
+ return rtc_valid_tm(time);
}
static int mrst_set_time(struct device *dev, struct rtc_time *time)
@@ -119,9 +122,9 @@ static int mrst_set_time(struct device *dev, struct rtc_time *time)
min = time->tm_min;
sec = time->tm_sec;
- if (yrs < 70 || yrs > 138)
+ if (yrs < 72 || yrs > 138)
return -EINVAL;
- yrs -= 60;
+ yrs -= 72;
spin_lock_irqsave(&rtc_lock, flags);
--
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