Messages in this thread | | | Date | Tue, 25 Jul 2006 15:07:47 -0400 | From | Neil Horman <> | Subject | Re: [PATCH] RTC: Add mmap method to rtc character driver |
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On Tue, Jul 25, 2006 at 08:56:14PM +0200, Segher Boessenkool wrote: > >>Similar functionality is already available via VDSO on > >>platforms that support it (currently PowerPC and AMD64?) -- > >>seems like a better way forward. > >> > >In general I agree, but that only works if you operate on a > >platform that > >supports virtual syscalls, and has vdso configured. > > That's why I said "a better way forward", not "this already > works everywhere". > > >I'm not overly familiar > >with vdso, but I didn't think vdso could be supported on all > >platforms/arches. > > Oh? Which can not, and why? > I'm sorry, I shouldn't say that vdso itself can't be supported, but rather a vsyscall that doesn't just wind up trapping into the kernel anyway. Older systems without a hpet timer to map into user space jump immediately to mind. Arjan had mentioned a calibration on rdtsc as another alternative, which I had not considered, so this may all be moot, but I was worried that a vdso solution wouldn't always give the X guys what they were really after.
Regards Neil
> > Segher
-- /*************************************************** *Neil Horman *Software Engineer *gpg keyid: 1024D / 0x92A74FA1 - http://pgp.mit.edu ***************************************************/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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