linux-kernel - Re: [PATCH 00/51] rtc: stop using rtc deprecated functions

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Message-ID: <CA+M3ks68+z6nDtYM8CDpso7SxjB6Nt5E=rOc1yxx=kDz6PUeVQ@mail.gmail.com>
Date:   Tue, 20 Jun 2017 17:07:46 +0200
From:   Benjamin Gaignard <benjamin.gaignard@...aro.org>
To:     Alexandre Belloni <alexandre.belloni@...e-electrons.com>
Cc:     Pavel Machek <pavel@....cz>,
        Steve Twiss <stwiss.opensource@...semi.com>,
        "linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
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        Alessandro Zummo <a.zummo@...ertech.it>,
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Subject: Re: [PATCH 00/51] rtc: stop using rtc deprecated functions

2017-06-20 15:48 GMT+02:00 Alexandre Belloni
<alexandre.belloni@...e-electrons.com>:
> On 20/06/2017 at 15:44:58 +0200, Pavel Machek wrote:
>> On Tue 2017-06-20 13:37:22, Steve Twiss wrote:
>> > Hi Pavel,
>> >
>> > On 20 June 2017 14:26, Pavel Machek wrote:
>> >
>> > > Subject: Re: [PATCH 00/51] rtc: stop using rtc deprecated functions
>> > >
>> > > On Tue 2017-06-20 14:24:00, Alexandre Belloni wrote:
>> > > > On 20/06/2017 at 14:10:11 +0200, Pavel Machek wrote:
>> > > > > On Tue 2017-06-20 12:03:48, Alexandre Belloni wrote:
>> > > > > > On 20/06/2017 at 11:35:08 +0200, Benjamin Gaignard wrote:
>> > > > > > > rtc_time_to_tm() and rtc_tm_to_time() are deprecated because they
>> > > > > > > rely on 32bits variables and that will make rtc break in y2038/2016.
>> > > > > >
>> > > > > > Please don't, because this hide the fact that the hardware will not
>> > > > > > handle dates in y2038 anyway and as pointed by Russell a few month ago,
>> > > > > > rtc_time_to_tm will be able to catch it but the 64 bit version will
>> > > > > > silently ignore it.
>> > > > >
>> > > > > Reference? Because rtc on PCs stores date in binary coded decimal, so
>> > > > > it is likely to break in 2100, not 2038...
>> > > >
>> > > > I'm not saying it should be done but clearly, that is not the correct
>> > > > thing to do for RTCs that are using a single 32 bits register to store
>> > > > the time.
>> > > > You give one example, I can give you three: armada38x, at91sam9,
>> > > > at32ap700x and that just in the beginning of the series.
>> > >
>> > > I wanted reference to Russell's mail.
>> >
>> > This is it.
>> > https://patchwork.kernel.org/patch/6219401/
>>
>> Thanks.
>>
>> Yes, that's argument against changing rtc _drivers_ for hardware that
>> can not do better than 32bit. For generic code (such as 44/51 sysfs,
>> 51/51 suspend test), the change still makes sense.

What I had in mind when writing those patches was to remove the limitations
coming from those functions usage, even more since they been marked has
deprecated.

I agree that will change nothing of hardware limitation but at least
the limit will
not come from the framework.

>>
>
> Yes, we agree on that but I won't cherry pick working patches from a 51
> patches series.

maybe only the acked ones ?

>
>
> --
> Alexandre Belloni, Free Electrons
> Embedded Linux and Kernel engineering
> http://free-electrons.com