/dev/rtc on alpha

[Bob McElrath <bob+linux-kernel@mcelrath.org>]

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In a nutshell, the rtc driver on alpha does not work.  This is easily
verified with the small program in Documentation/rtc.txt -- all ioctl's
fail.  (I tried on an LX164 and a CS20)  That's the /dev/rtc driver
drivers/char/rtc.c.  I'd like to make it work but don't understand
what's going on with the rtc interrupt in arch/alpha/kernel/*.  So, can
some expert comment on this situation for me?

The /dev/rtc driver builds and loads fine but the define RTC_IRQ is not
set in include/asm-alpha/mc146818rtc.h.  Naievely setting it, the driver
still builds and loads, but is unable to grab the interrupt (IRQ 8)
because the code in arch/alpha/kernel grabbed it first.

Why is the alpha kernel code grabbing the rtc interrupt?  Is it possible
it share its use with a user program?  Would reprogramming the interrupt
rate by a user program do violence to some internel kernel timing?

Thanks,
Bob McElrath [Univ. of California at Davis, Department of Physics]

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