[patch 8/8] acpi: fix BDC handling in drivers/acpi/sleep/proc.c

[patch 8/8] acpi: fix BDC handling in drivers/acpi/sleep/proc.c

[akpm]

From: Linus Torvalds <torvalds@linux-foundation.org>

That code is doing all the arithmetic in non-BCD mode, but the "adjust"
case doesn't do a BCD_TO_BIN() on that arithmetic.

In other words, the logic you removed was certainly total crap, but there's
more crap remaining inside the "if (adjust)" logic.  I just suspect you
never tested that part (ie using a string that starts with '+').

In fact, for the non-broken case, the old broken code *should* have been a
no-op, since it did BIN_TO_BCD() followed by BCD_TO_BIN().  It then totally
stupidly seemed to expect that the "adjust" case would do a BCD addition! 
So I don't even see why your patch should have mattered or worked!

So how about this cleanup instead? Does this work for you?

NOTE! I wanted to switch "acpi_system_alarm_seq_show()" over to this too,
but that code has a strange rule:

        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);

and note the "& 0x3f" which is done in BCD mode. Strange. But we always
write zero (which may or may not be correct). So I'd have to add a mask to
the interface, and I decided it wasn't worth it until somebody talks about
how that thing actually works..

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Lord <lkml@rtr.ca>
Cc: David Brownell <david-b@pacbell.net>
Cc: <borntraeger@de.ibm.com>
Cc: Len Brown <lenb@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 drivers/acpi/sleep/proc.c |   66 +++++++++++++++---------------------
 1 file changed, 29 insertions(+), 37 deletions(-)

diff -puN drivers/acpi/sleep/proc.c~acpi-fix-bdc-handling-in-drivers-acpi-sleep-procc drivers/acpi/sleep/proc.c
--- a/drivers/acpi/sleep/proc.c~acpi-fix-bdc-handling-in-drivers-acpi-sleep-procc
+++ a/drivers/acpi/sleep/proc.c
@@ -194,6 +194,23 @@ static int get_date_field(char **p, u32 
 	return result;
 }
 
+/* Read a possibly BCD register, always return binary */
+static u32 cmos_bcd_read(int offset, int rtc_control)
+{
+	u32 val = CMOS_READ(offset);
+	if (!(rtc_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
+		BCD_TO_BIN(val);
+	return val;
+}
+
+/* Write binary value into possibly BCD register */
+static void cmos_bcd_write(u32 val, int offset, int rtc_control)
+{
+	if (!(rtc_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
+		BIN_TO_BCD(val);
+	CMOS_WRITE(val, offset);
+}
+
 static ssize_t
 acpi_system_write_alarm(struct file *file,
 			const char __user * buffer, size_t count, loff_t * ppos)
@@ -258,35 +275,18 @@ acpi_system_write_alarm(struct file *fil
 	spin_lock_irq(&rtc_lock);
 
 	rtc_control = CMOS_READ(RTC_CONTROL);
-	if (!(rtc_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
-		BIN_TO_BCD(yr);
-		BIN_TO_BCD(mo);
-		BIN_TO_BCD(day);
-		BIN_TO_BCD(hr);
-		BIN_TO_BCD(min);
-		BIN_TO_BCD(sec);
-	}
 
 	if (adjust) {
-		yr += CMOS_READ(RTC_YEAR);
-		mo += CMOS_READ(RTC_MONTH);
-		day += CMOS_READ(RTC_DAY_OF_MONTH);
-		hr += CMOS_READ(RTC_HOURS);
-		min += CMOS_READ(RTC_MINUTES);
-		sec += CMOS_READ(RTC_SECONDS);
+		yr += cmos_bcd_read(RTC_YEAR, rtc_control);
+		mo += cmos_bcd_read(RTC_MONTH, rtc_control);
+		day += cmos_bcd_read(RTC_DAY_OF_MONTH, rtc_control);
+		hr += cmos_bcd_read(RTC_HOURS, rtc_control);
+		min += cmos_bcd_read(RTC_MINUTES, rtc_control);
+		sec += cmos_bcd_read(RTC_SECONDS, rtc_control);
 	}
 
 	spin_unlock_irq(&rtc_lock);
 
-	if (!(rtc_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
-		BCD_TO_BIN(yr);
-		BCD_TO_BIN(mo);
-		BCD_TO_BIN(day);
-		BCD_TO_BIN(hr);
-		BCD_TO_BIN(min);
-		BCD_TO_BIN(sec);
-	}
-
 	if (sec > 59) {
 		min++;
 		sec -= 60;
@@ -307,14 +307,6 @@ acpi_system_write_alarm(struct file *fil
 		yr++;
 		mo -= 12;
 	}
-	if (!(rtc_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
-		BIN_TO_BCD(yr);
-		BIN_TO_BCD(mo);
-		BIN_TO_BCD(day);
-		BIN_TO_BCD(hr);
-		BIN_TO_BCD(min);
-		BIN_TO_BCD(sec);
-	}
 
 	spin_lock_irq(&rtc_lock);
 	/*
@@ -326,9 +318,9 @@ acpi_system_write_alarm(struct file *fil
 	CMOS_READ(RTC_INTR_FLAGS);
 
 	/* write the fields the rtc knows about */
-	CMOS_WRITE(hr, RTC_HOURS_ALARM);
-	CMOS_WRITE(min, RTC_MINUTES_ALARM);
-	CMOS_WRITE(sec, RTC_SECONDS_ALARM);
+	cmos_bcd_write(hr, RTC_HOURS_ALARM, rtc_control);
+	cmos_bcd_write(min, RTC_MINUTES_ALARM, rtc_control);
+	cmos_bcd_write(sec, RTC_SECONDS_ALARM, rtc_control);
 
 	/*
 	 * If the system supports an enhanced alarm it will have non-zero
@@ -336,11 +328,11 @@ acpi_system_write_alarm(struct file *fil
 	 * to the RTC area of memory.
 	 */
 	if (acpi_gbl_FADT.day_alarm)
-		CMOS_WRITE(day, acpi_gbl_FADT.day_alarm);
+		cmos_bcd_write(day, acpi_gbl_FADT.day_alarm, rtc_control);
 	if (acpi_gbl_FADT.month_alarm)
-		CMOS_WRITE(mo, acpi_gbl_FADT.month_alarm);
+		cmos_bcd_write(mo, acpi_gbl_FADT.month_alarm, rtc_control);
 	if (acpi_gbl_FADT.century)
-		CMOS_WRITE(yr / 100, acpi_gbl_FADT.century);
+		cmos_bcd_write(yr / 100, acpi_gbl_FADT.century, rtc_control);
 	/* enable the rtc alarm interrupt */
 	rtc_control |= RTC_AIE;
 	CMOS_WRITE(rtc_control, RTC_CONTROL);
_

Re: [patch 8/8] acpi: fix BDC handling in drivers/acpi/sleep/proc.c

[David Brownell]

By the way, another longstanding bug in this /proc/acpi/... code is:

> @@ -336,11 +328,11 @@ acpi_system_write_alarm(struct file *fil
>  	 * to the RTC area of memory.
>  	 */
>  	if (acpi_gbl_FADT.day_alarm)
> -		CMOS_WRITE(day, acpi_gbl_FADT.day_alarm);
> +		cmos_bcd_write(day, acpi_gbl_FADT.day_alarm, rtc_control);
>  	if (acpi_gbl_FADT.month_alarm)
> -		CMOS_WRITE(mo, acpi_gbl_FADT.month_alarm);
> +		cmos_bcd_write(mo, acpi_gbl_FADT.month_alarm, rtc_control);
>  	if (acpi_gbl_FADT.century)
> -		CMOS_WRITE(yr / 100, acpi_gbl_FADT.century);
> +		cmos_bcd_write(yr / 100, acpi_gbl_FADT.century, rtc_control);

The "century" field is unrelated to the alarm.  It's purely
a way to distinguish 19xx vs 20xx (and 21xx, etc).

>  	/* enable the rtc alarm interrupt */
>  	rtc_control |= RTC_AIE;
>  	CMOS_WRITE(rtc_control, RTC_CONTROL);