Return an error if the user tries to set an alarm that isn't
supported by the hardware.

Signed-off-by: Gabriele Mazzotta <[email protected]>
---
 drivers/rtc/rtc-cmos.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
index 4cdb335..b3f9298 100644
--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c
@@ -336,6 +336,26 @@ static int cmos_set_alarm(struct device *dev, struct 
rtc_wkalrm *t)
        if (!is_valid_irq(cmos->irq))
                return -EIO;
 
+       if (!cmos->mon_alrm || !cmos->day_alrm) {
+               struct rtc_time now;
+               time64_t t_now;
+               time64_t t_alrm;
+
+               cmos_read_time(dev, &now);
+               t_now = rtc_tm_to_time64(&now);
+               t_alrm = rtc_tm_to_time64(&t->time);
+               if (!cmos->day_alrm && (t_alrm - t_now) > (24 * 60 * 60)) {
+                       dev_err(dev,
+                               "Alarms can be up to one day in the future\n");
+                       return -EINVAL;
+               }
+               if (!cmos->mon_alrm && (t_alrm - t_now) > (31 * 24 * 60 * 60)) {
+                       dev_err(dev,
+                               "Alarms can be up to 31 days in the future\n");
+                       return -EINVAL;
+               }
+       }
+
        mon = t->time.tm_mon + 1;
        mday = t->time.tm_mday;
        hrs = t->time.tm_hour;
-- 
2.9.3

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