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

[John Stultz <john.stultz@linaro.org>]

On 04/24/2013 12:44 PM, Kay Sievers wrote:
> On Wed, Apr 24, 2013 at 8:32 PM, John Stultz <john.stultz@linaro.org> 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