Re: [RFE PATCH 2/2] rtc, add write functionality to sysfs

[Prarit Bhargava <prarit-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

On 02/23/2013 06:11 PM, Alessandro Zummo wrote:
> On 22/feb/2013, at 22:05, John Stultz <john.stultz-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org> wrote:
> 
>> On 02/22/2013 12:55 PM, Prarit Bhargava wrote:
>>>
>>> On 02/22/2013 03:43 PM, John Stultz wrote:
>>>> On 02/14/2013 09:02 AM, Prarit Bhargava wrote:
>>>>> /sys/class/rtc/rtcX/date and /sys/class/rtc/rtcX/time currently have
>>>>> read-only access.  This patch introduces write functionality which will
>>>>> set the rtc time.
>>>>>
>>>>> Usage: echo YYYY-MM-DD > /sys/class/rtc/rtcX/date
>>>>>         echo HH:MM:SS > /sys/class/rtc/rtcX/time
>>>> Why do we want to add a new interface here?
>>> John,
>>>
>>> I'm not adding a new interface.  The current date/time interface only handles
>>> read and I'm introducing write.
>>>
>>
>> Right, but what benefit does that provide?
>> (I'm not saying there isn't any, its just not clear from your patch why this is a good thing.)
>>

Sorry John, I misunderstood your question.

>> Also CC'ing Alessandro for his input.
> 
> I'd like to keep the interfaces as simple as possible but I'm open to improvements if there are good use cases.
> 

AFAICT there is no way for me to "test" or use the write from userspace.
hwclock uses the SET_TIME ioctl, which is a different code path AFAICT.

I'd like to be at least able to test this stuff when we make changes to it so I
think having write functionality for date & time is worthwhile.

For me, I'm using these to heavily test ntp and ntpdate over system reboots.

OOC, Alessandro, why is the date & time split into two fields?

P.