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SubjectRe: PATCH: /proc/acpi/alarm: handle day-of-month wraparound on readback
Mark Lord wrote:
> 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).
..

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,
and noticed the bug over this past weekend (2008-11-30).

>
> 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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