Thanks lmaza for responding.
I am very excited about learning this Linux kernel.
The Linux initiative is very important (even historically)
at this time. The ability to collaborate on such a scale is
tremendous.
Code:
mod_timer(&rtc_irq_timer, jiffies + HZ/rtc_freq + 2*HZ/100);
The analysis of this expression is not primarily to detail
the 2nd parameter of the mod_timer() call. It is to predict
what code the compiler might generate. Of course, this type
of analysis is normally somewhat bizarre. However, consider
the side effect of an unnecessary multi-precision or
floating point expression in this interrupt handler.
Any reasonable optimization is advisable, if it improves the
system wide interrupt latency.
The term "+ HZ/rtc_freq +" appears to be a constant divided
by an 'unsigned long'. It looks like the preprocessor will
not be able to perform this division, so run time execution
will result.
I am in the habit of holding my interrupt handlers to very
tight scrutiny for execution cycles.