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SubjectPATCH: /proc/acpi/alarm: handle day-of-month wraparound on readback
Fix month wrap issue with readback from /proc/acpi/alarm
This bug has been around *forever*.

$ echo '2008-12-01 10:36:20' > /proc/acpi/alarm
$ cat /proc/acpi/alarm
2008-11-01 10:36:20
Note how the readback above shows the month incorrectly.
But with this patch applied, it shows the correct month (12).

Patch applies/works on kernels 2.6.25.* through 2.6.27.*,
and probably on earlier kernels as well.

Probably best to queue it up for the next major cycle.

Signed-off-by: Mark Lord <mlord@pobox.com>

--- linux-2.6.25/drivers/acpi/sleep/proc.c 2008-06-09 14:27:19.000000000 -0400
+++ linux/drivers/acpi/sleep/proc.c 2008-11-30 18:08:31.000000000 -0500
@@ -84,12 +84,15 @@
#define HAVE_ACPI_LEGACY_ALARM
#endif

+static u32 cmos_bcd_read(int offset, int rtc_control);
+
#ifdef HAVE_ACPI_LEGACY_ALARM

static int acpi_system_alarm_seq_show(struct seq_file *seq, void *offset)
{
u32 sec, min, hr;
u32 day, mo, yr, cent = 0;
+ u32 today = 0;
unsigned char rtc_control = 0;
unsigned long flags;

@@ -97,38 +100,32 @@

spin_lock_irqsave(&rtc_lock, flags);

- sec = CMOS_READ(RTC_SECONDS_ALARM);
- min = CMOS_READ(RTC_MINUTES_ALARM);
- hr = CMOS_READ(RTC_HOURS_ALARM);
rtc_control = CMOS_READ(RTC_CONTROL);
+ sec = cmos_bcd_read(RTC_SECONDS_ALARM, rtc_control);
+ min = cmos_bcd_read(RTC_MINUTES_ALARM, rtc_control);
+ hr = cmos_bcd_read(RTC_HOURS_ALARM, rtc_control);

/* If we ever get an FACP with proper values... */
- if (acpi_gbl_FADT.day_alarm)
+ if (acpi_gbl_FADT.day_alarm) {
/* ACPI spec: only low 6 its should be cared */
day = CMOS_READ(acpi_gbl_FADT.day_alarm) & 0x3F;
- else
- day = CMOS_READ(RTC_DAY_OF_MONTH);
+ if (!(rtc_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
+ BCD_TO_BIN(day);
+ } else
+ day = cmos_bcd_read(RTC_DAY_OF_MONTH, rtc_control);
if (acpi_gbl_FADT.month_alarm)
- mo = CMOS_READ(acpi_gbl_FADT.month_alarm);
- else
- mo = CMOS_READ(RTC_MONTH);
+ mo = cmos_bcd_read(acpi_gbl_FADT.month_alarm, rtc_control);
+ else {
+ mo = cmos_bcd_read(RTC_MONTH, rtc_control);
+ today = cmos_bcd_read(RTC_DAY_OF_MONTH, rtc_control);
+ }
if (acpi_gbl_FADT.century)
- cent = CMOS_READ(acpi_gbl_FADT.century);
+ cent = cmos_bcd_read(acpi_gbl_FADT.century, rtc_control);

- yr = CMOS_READ(RTC_YEAR);
+ yr = cmos_bcd_read(RTC_YEAR, rtc_control);

spin_unlock_irqrestore(&rtc_lock, flags);

- if (!(rtc_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
- BCD_TO_BIN(sec);
- BCD_TO_BIN(min);
- BCD_TO_BIN(hr);
- BCD_TO_BIN(day);
- BCD_TO_BIN(mo);
- BCD_TO_BIN(yr);
- BCD_TO_BIN(cent);
- }
-
/* we're trusting the FADT (see above) */
if (!acpi_gbl_FADT.century)
/* If we're not trusting the FADT, we should at least make it
@@ -153,6 +150,20 @@
else
yr += cent * 100;

+ /*
+ * Show correct dates for alarms up to a month into the future.
+ * This solves issues for nearly all situations with the common
+ * 30-day alarm clocks in PC hardware.
+ */
+ if (day < today) {
+ if (mo < 12) {
+ mo += 1;
+ } else {
+ mo = 1;
+ yr += 1;
+ }
+ }
+
seq_printf(seq, "%4.4u-", yr);
(mo > 12) ? seq_puts(seq, "**-") : seq_printf(seq, "%2.2u-", mo);
(day > 31) ? seq_puts(seq, "** ") : seq_printf(seq, "%2.2u ", day);

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