While 0e36a9a4a788e4e92407774df76c545910810d35 made sure that active

alarms were never returned with invalid "wildcard" fields (negative),

it can still report (wrongly) that the alarm triggers in the past.
Example, if it's now 10am, an alarm firing at 5am will be triggered

TOMORROW not today.  (Which may also be next month or next year...)
This updates that alarm handling in three ways:
  * Handle alarm rollover in the common cases of RTCs that don't

    support matching on all date fields.
  * Skip the invalid-field logic when it's not needed.
  * Minor bugfix ... tm_isdst should be ignored, it's one of the

    fields Linux doesn't maintain.
A warning is emitted for some of the unhandled rollover cases, but

the possible combinations are a bit too numerous to handle every

bit of potential hardware and firmware braindamage.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>

---

 drivers/rtc/interface.c |  102 ++++++++++++++++++++++++++++++++++++++++++------

 1 file changed, 91 insertions(+), 11 deletions(-)
--- a/drivers/rtc/interface.c	2008-06-21 19:51:24.000000000 -0700

+++ b/drivers/rtc/interface.c	2008-06-22 13:05:57.000000000 -0700

@@ -126,12 +126,25 @@ int rtc_read_alarm(struct rtc_device *rt

 	int err;

 	struct rtc_time before, now;

 	int first_time = 1;

+	unsigned long t_now, t_alm;

+	enum { none, day, month, year } missing = none;

+	unsigned days;
-	/* The lower level RTC driver may not be capable of filling

-	 * in all fields of the rtc_time struct (eg. rtc-cmos),

-	 * and so might instead return -1 in some fields.

-	 * We deal with that here by grabbing a current RTC timestamp

-	 * and using values from that for any missing (-1) values.

+	/* The lower level RTC driver may return -1 in some fields,

+	 * creating invalid alarm->time values, for reasons like:

+	 *

+	 *   - The hardware may not be capable of filling them in;

+	 *     many alarms match only on time-of-day fields, not

+	 *     day/month/year calendar data.

+	 *

+	...
[ message continues ]

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, rt...
[ message continues ]

We've had some BCD_TO_BIN() changes here in 2.6.28 already,

does 2.6.28-rc still have this bug?
I'd check myself, but I don't have a /proc/acpi/alarm due to this:
#if defined(CONFIG_RTC_DRV_CMOS) || defined(CONFIG_RTC_DRV_CMOS_MODULE) ||

!defined(CONFIG_X86)

/* use /sys/class/rtc/rtcX/wakealarm instead; it's not ACPI-specific */

#else

#define HAVE_ACPI_LEGACY_ALARM

#endif
thanks,

-Len
--

..
Yeah.. bit of a nuisance that.

I regularly apply this patch to my own kernels:
--- old/drivers/acpi/sleep/proc.c	2008-01-06 16:39:45.000000000 -0500

+++ linux/drivers/acpi/sleep/proc.c	2008-01-06 17:35:35.000000000 -0500

@@ -78,11 +78,11 @@

 }

 #endif				/* CONFIG_ACPI_PROCFS */
-#if defined(CONFIG_RTC_DRV_CMOS) || defined(CONFIG_RTC_DRV_CMOS_MODULE) || !defined(CONFIG_X86)

+//#if defined(CONFIG_RTC_DRV_CMOS) || defined(CONFIG_RTC_DRV_CMOS_MODULE) || !defined(CONFIG_X86)

 /* use /sys/class/rtc/rtcX/wakealarm instead; it's not ACPI-specific */

-#else

+//#else

 #define	HAVE_ACPI_LEGACY_ALARM

-#endif

+//#endif
 #ifdef	HAVE_ACPI_LEGACY_ALARM
--

On Mon, 01 Dec 2008 17:15:46 -0500
 While it will certainly work, maybe it's time to switch

 to /sys/class/rtc/rtcX/wakealarm . 
-- 
 Best regards,
 Alessandro Zummo,

  Tower Technologies - Torino, Italy
  http://www.towertech.it
--

Len Brown wrote:

..
Yes, bug still there.  Here is a version of the patch for 2.6.28-rc6
---snip---
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).
This patch applies/works on 2.6.28-rc6.

Probably best to queue it up for the next major cycle.
Signed-off-by: Mark Lord <mlord@pobox.com> 
--- linux/drivers/acpi/sleep/proc.c	2008-11-20 18:19:22.000000000 -0500

+++ linux-2.6.28-rc6/drivers/acpi/sleep/proc.c	2008-12-01 17:07:51.000000000 -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)

+			day = bcd2bin(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_MONT...
[ message continues ]

..
I should add, that the above test requires that the alarm

be set for any day of the *next* month from the current month.

My MythTV box does a readback test any time it programs a wakeup,

--

On Sun, 22 Jun 2008 20:42:13 -0700
 Acked-by: Alessandro Zummo <a.zummo@towertech.it>
-- 
 Best regards,
 Alessandro Zummo,

  Tower Technologies - Torino, Italy
  http://www.towertech.it
--