Re: [PATCH] time: Revert ALWAYS_USE_PERSISTENT_CLOCK compile time optimizaitons

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On 04/24/2013 11:41 AM, Kay Sievers wrote:
On Wed, Apr 24, 2013 at 8:32 PM, John Stultz <john.stultz@xxxxxxxxxx> wrote:
Kay Sievers noted that the ALWAYS_USE_PERSISTENT_CLOCK config,
which enables some minor compile time optimization to avoid
uncessary code in mostly the suspend/resume path could cause
problems for userland.

In particular, the dependency for RTC_HCTOSYS on
!ALWAYS_USE_PERSISTENT_CLOCK, which avoids setting the time
twice and simplifies suspend/resume, has the side effect
of causing the /sys/class/rtc/rtcN/hctosys flag to always be
zero, and this flag is commonly used by udev to setup the
/dev/rtc symlink to /dev/rtcN, which can cause pain for
older applications.
FWIW, in the light of the original change, I've just removed the
/dev/rtc creation from the default udev rules now, so that thing will
be phased out in the future.
Is that actually wanted? What happens to applications that use /dev/rtc?

I think setting up the /dev/rtc link is important. Its just that setting it up exclusively by the hctosys flag is maybe more fragile then we'd like. Instead the hctosys flag maybe should only be used as a hint if there is more then one RTC available.

thanks
-john
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