Messages in this thread | | | Date | Tue, 25 Jul 2006 16:29:27 -0700 (PDT) | From | David Lang <> | Subject | Re: [PATCH] RTC: Add mmap method to rtc character driver |
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On Tue, 25 Jul 2006, Neil Horman wrote:
>> >> Quick hacks are frowned upon in the Linux universe. The kernel-user >> space interface is supposed to be stable, and thus a hack like this has >> to be maintained indefinitely. >> >> Putting temporary hacks like this in is not a good idea. >> > Only if you make the mental leap that this is a hack; its not. Its a new > feature for a driver. mmap on device drivers is a well known and understood > interface. There is nothing hackish about it. And there is no need for it to > be temporary either. Why shouldn't the rtc driver be able to export a monotonic > counter via the mmap interface? mmtimer does it already, as do many other > drivers. Theres nothing unstable about this interface, and it need not be short > lived. It can live in perpituity, and applications can choose to use it, or > migrate away from it should something else more efficient become available (a > gettimeofday vsyscall). More importantly, it can continue to be used in those > situations where a vsyscall is not feasable, or simply maps to the nominal slow > path kernel trap that one would find to heavy-weight to use in comparison to an > mmaped page.
given that this won't go into 2.6.18 at this point, isn't there time to figure out the gettimeofday vsyscall before the 2.6.19 merge window? (in a month or so). even if you have to wait until 2.6.20 it's unlikly that any apps could be released with an interface to /dev/rtc rather then waiting a little bit for the better interface.
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