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 ]

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

--

[ 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, ...
[ 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,
--

[ message continues ]

Why not just use the new RTC drivers and /sys/class/rtc/rtc0/wakealarm?
MythTV already provides seconds since epoch for the wakeup time, so you
can use this value without converting it:

$ cat /usr/local/bin/myth-setwaketime
#!/bin/sh

SYSFS_WAKE_FILE="/sys/class/rtc/rtc0/wakealarm"

echo -n "Wakeup time is "
date -d @$1

if ! test -w "$SYSFS_WAKE_FILE" ; then
	exit 1
fi

echo 0 > "$SYSFS_WAKE_FILE"
echo "$1" > "$SYSFS_WAKE_FILE"
--

[ message continues ]

..

That question has nothing to do with fixing the bug in
the /proc/acpi/alarm code.  The bug is still there whether
I personally use a different mechanism or not!  :)

But in answer to your question, the new RTC drivers *also* fail
for some other reason.  They did work up until the HPET integration
(back in 2.6.26 ?), but have not worked since.

My MythTV box always tries the new ones, and if the readback test
fails to agree with what was attempted, it then falls back to
the old yet more reliable /proc/acpi/alarm.

I haven't really had time to find the exact breakage point and patch it
in the new RTC code yet (I put about 10 hours into it back then,
with no useful result), but the old code does have a useful fix.

Thus this thread.

Cheers
--

[ 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

--

[ message continues ]

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_MONTH);
+		mo = ...
[ message continues ]

(repost)

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
when the alarm is set in the *next* calendar month.
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>

--- old/drivers/acpi/sleep/proc.c	2008-11-20 18:19:22.000000000 -0500
+++ 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_MONTH);
+		mo = cmos_bcd_read(acpi_gbl_FADT.month_alarm, ...
[ message continues ]

> (repost)

thanks for the refresh, Mark.
applied to acpi-test.

--
Len Brown, Intel Open Source Technology Center
--

[ message continues ]

..

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
 
--

[ message continues ]

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

--

[ message continues ]

..

Perhaps, but doing so would still leave the but in /proc/acpi/alarm,
so we need to fix it regardless.

Cheers
--

[ message continues ]