Messages in this thread | | | From | Segher Boessenkool <> | Subject | Re: [PATCH] RTC: Add mmap method to rtc character driver | Date | Tue, 25 Jul 2006 19:57:30 +0200 |
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> 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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