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

From: Kay Sievers
Date: Wed Apr 24 2013 - 15:45:20 EST

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?

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