Real-Time Clocks and POSIX

Real-Time Clocks and POSIX

[Pilhofer, Frank]

Hi,
 
I'm looking into real-time clocks.  I'm wondering why the POSIX
clock_* and timer_* APIs are not used for RTCs.  E.g., I expected
that you would be able to just use:

  struct timespec now;
  clock_gettime (MY_RTC_DEVICE, &now);

to read the time from a RTC device.  There even appears to be an easy
way to register auxiliary clocks in kernel/posix-timers.c.

Instead, Documentation/rtc.txt describes the "ioctl" API that is to
be used instead.

Is there a motivation for not using the POSIX functions for RTCs?
Or is there a code path between the two that I did not see?

Thank you,
Frank

Re: Real-Time Clocks and POSIX

[Uwe Kleine-König]

Hello Frank,

On Tue, Jul 28, 2009 at 01:21:48PM -0400, Pilhofer, Frank wrote:
> I'm looking into real-time clocks.
This is the wrong forum for real-time clocks.  This list is about
realtime systems, not clocks.  The relevant MAINTAINER entry for you is:

	REAL TIME CLOCK (RTC) SUBSYSTEM
	P:      Alessandro Zummo
	M:      a.zummo@towertech.it
	L:      rtc-linux@googlegroups.com
	S:      Maintained
	F:      Documentation/rtc.txt
	F:      drivers/rtc/
	F:      include/linux/rtc.h

Best regards
Uwe

-- 
Pengutronix e.K.                              | Uwe Kleine-König            |
Industrial Linux Solutions                    | http://www.pengutronix.de/  |
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