Not really. This introduces a potentially very difficult supportWell, you do actually know when they want to look at it. The rtc driver only
user-visible interface. Consider a tickless kernel -- you might end up
taking tick interrupts ONLY to update this page, since you don't have
any way of knowing when userspace wants to look at it.
unmasks its interrupt when a user space process has opened the device and sent
it a RTC_UIE ON or RTC_PIE_ON (or other shuch ioctl). So if you open /dev/rtc,
and memory map the page, but never enable a timer method, then every read of the
page returns zero. The only overhead this patch is currently adding, execution
time-wise is the extra time it takes to write to a the shared page variable. If
the timer tick interrupt is executing, its because someone is reading tick data,
or plans to very soon.