rtc: add alarm/update irq interfaces

Add standard interfaces for alarm/update irqs enabling.  Drivers are no
more required to implement equivalent ioctl code as rtc-dev will provide
it.

UIE emulation should now be handled correctly and will work even for those
RTC drivers who cannot be configured to do both UIE and AIE.

Signed-off-by: Alessandro Zummo <a.zummo@towertech.it>
Cc: David Brownell <david-b@pacbell.net>
Cc: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Cc: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 1 deletions

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 123092d8a984..165a81843357 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -102,9 +102,13 @@ config RTC_INTF_DEV_UIE_EMUL
         depends on RTC_INTF_DEV
         help
           Provides an emulation for RTC_UIE if the underlying rtc chip
-          driver does not expose RTC_UIE ioctls.  Those requests generate
+          driver does not expose RTC_UIE ioctls. Those requests generate
           once-per-second update interrupts, used for synchronization.
 
+          The emulation code will read the time from the hardware
+          clock several times per second, please enable this option
+          only if you know that you really need it.
+
 config RTC_DRV_TEST
         tristate "Test driver/device"
         help