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    SubjectRe: [PATCH] RTC: Add mmap method to rtc character driver
    Date
    > 	At OLS last week, During Dave Jones Userspace Sucks presentation, Jim
    > Geddys and some of the Xorg guys noted that they would be able to
    > stop using gettimeofday
    > so frequently, if they had some other way to get a millisecond
    > resolution timer
    > in userspace, one that they could perhaps read from a memory mapped
    > page. I was
    > right behind them and though that seemed like a reasonable
    > request, so I've
    > taken a stab at it. This patch allows for a page to be mmaped
    > from /dev/rtc
    > character interface, the first 4 bytes of which provide a regularly
    > increasing
    > count, once every rtc interrupt. The frequency is of course
    > controlled by the
    > regular ioctls provided by the rtc driver. I've done some basic
    > testing on it,
    > and it seems to work well.

    Similar functionality is already available via VDSO on
    platforms that support it (currently PowerPC and AMD64?) --
    seems like a better way forward.


    Segher

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