Due to rtc-acpid and efi time used the same logic for computing
week day, so this patch moves code to rtc.h header file.
Additionally using a leap year algorithm to replace the for-loop
block in compute_wday for improve the performance. The first
version of algorithm is from Oliver Neukum.
---
drivers/rtc/rtc-acpitad.c | 13 +------------
include/linux/efi.h | 13 +------------
include/linux/rtc.h | 38 ++++++++++++++++++++++++++++++++++++++
3 files changed, 40 insertions(+), 24 deletions(-)
diff --git a/drivers/rtc/rtc-acpitad.c b/drivers/rtc/rtc-acpitad.c
index 065a033..bdf7ae1 100644
--- a/drivers/rtc/rtc-acpitad.c
+++ b/drivers/rtc/rtc-acpitad.c
@@ -32,23 +32,12 @@ compute_yday(struct acpi_time *acpit)
static int
compute_wday(struct acpi_time *acpit)
{
- int y;
- int ndays = 0;
-
if (acpit->year < 1900) {
pr_err("ACPI year < 1900, invalid date\n");
return -1;
}
- for (y = 1900; y < acpit->year; y++)
- ndays += 365 + (is_leap_year(y) ? 1 : 0);
-
- ndays += compute_yday(acpit);
-
- /*
- * 1=1/1/1900 was a Monday
- */
- return (ndays + 1) % 7;
+ return rtc_wday(acpit->day, acpit->month - 1, acpit->year);
}
static void
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 3859f3e..1c78ae7 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -177,23 +177,12 @@ compute_yday(efi_time_t *eft)
static inline int
compute_wday(efi_time_t *eft)
{
- int y;
- int ndays = 0;
-
if (eft->year < 1998) {
pr_err("EFI year < 1998, invalid date\n");
return -1;
}
- for (y = EFI_RTC_EPOCH; y < eft->year; y++)
- ndays += 365 + (is_leap_year(y) ? 1 : 0);
-
- ndays += compute_yday(eft);
-
- /*
- * 4=1/1/1998 was a Thursday
- */
- return (ndays + 4) % 7;
+ return rtc_wday(eft->day, eft->month - 1, eft->year);
}
static inline void
diff --git a/include/linux/rtc.h b/include/linux/rtc.h
index e6380ec..511884f 100644
--- a/include/linux/rtc.h
+++ b/include/linux/rtc.h
@@ -196,6 +196,44 @@ static inline bool is_leap_year(unsigned int year)
return (!(year % 4) && (year % 100)) || !(year % 400);
}
+#define SINCE1900 25 /* valid from 2000 */
+
+static inline int rtc_wday(unsigned int day, unsigned int month, unsigned int year)
+{
+ int ndays, correction;
+ int base;
+
+ if (year < 1900) {
+ pr_err("rtc: year < 1900, invalid date\n");
+ return -1;
+ }
+
+ if (year >= 2000)
+ base = year - 2000;
+ else
+ base = year - 1900;
+
+ correction = 0;
+ if (base >= 0) {
+ correction += base / 4;
+ correction -= base / 100;
+ correction += base / 400;
+ if (year >= 2000)
+ correction += SINCE1900;
+
+ /* later rtc_year_days will add the leap day of current year */
+ correction -= ((is_leap_year(year)) ? 1 : 0);
+ }
+
+ ndays = (year - 1900) * 365 + correction;
+ ndays += rtc_year_days(day, month, year);
+
+ /*
+ * 1=1/1/1900 was a Monday
+ */
+ return (ndays + 1) % 7;
+}
+
#ifdef CONFIG_RTC_HCTOSYS_DEVICE
extern int rtc_hctosys_ret;
#else
--
1.6.4.2
--
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