Re: [PATCH] RTC: Add mmap method to rtc character driver

[Neil Horman <nhorman@tuxdriver.com>]

On Tue, Jul 25, 2006 at 01:50:52PM -0700, H. Peter Anvin wrote:
> Neil Horman wrote:
> >
> >Agreed.  How about we take the /dev/rtc patch now (since its an added 
> >feature
> >that doesn't hurt anything if its not used, as far as tickless kernels 
> >go), and
> >I'll start working on doing gettimeofday in vdso for arches other than 
> >x86_64.
> >That will give the X guys what they wanted until such time until all the 
> >other
> >arches have a gettimeofday alternative that doesn't require kernel traps.
> >
> 
> It hurts if it DOES get used.
> 
Yes, but if its in trade for something thats being used currently which hurts
more (case in point being the X server), using this solution is a net gain.

I'm not arguing with you that adding a low res gettimeofday vsyscall is a better
long term solution, but doing that requires potentially several implementations
in the C library accross a range of architectures, some of which may not be able
to provide a time solution any better than what the gettimeofday syscall
provides today.  The /dev/rtc solution is easy, available right now, and applies
to all arches.  It has zero impact for systems which do not use it, and for
those applications which make a decision to use it instead of an alternate
method, the result I expect will be a net gain, until such time as we code up,
test and roll out a vsyscall solution 

Thanks & Regards
Neil 
> 	-hpa