Re: [PATCH] time: Revert ALWAYS_USE_PERSISTENT_CLOCK compile timeoptimizaitons

[John Stultz]

On 04/24/2013 12:44 PM, 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.
> An alternative to reverting this could be to set that flag
> unconditionally on the rtc that matches the persistent clock the
> kernel uses internally?
>
> I mean regardless of the pretty weird config option
> CONFIG_RTC_HCTOSYS_DEVICE, which internally just does a strcmp() with
> the given device name when the flag is queried. :)
>
> Can't we just have the same interface and your original optimization
> on x86, even without CONFIG_RTC_HCTOSYS_DEVICE enabled at all?

This might be possible, but I'd rather it be part of the unification 
work w/ the persistent_clock and the RTC code, rather then a quick hack.

thanks
-john

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