linux-kernel - Re: [PATCH v4 4/8] i2c: tegra: Support atomic transfers

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Date:   Tue, 14 Jan 2020 04:26:52 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Wolfram Sang <wsa@...-dreams.de>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        Mikko Perttunen <cyndis@...si.fi>, linux-i2c@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 4/8] i2c: tegra: Support atomic transfers

14.01.2020 01:52, Dmitry Osipenko пишет:
> 14.01.2020 01:03, Wolfram Sang пишет:
>> On Sun, Jan 12, 2020 at 08:14:26PM +0300, Dmitry Osipenko wrote:
>>> System shutdown may happen with interrupts being disabled and in this case
>>> I2C core rejects transfers if atomic transfer isn't supported by driver.
>>
>> Well, not quite. The core complains about it nowadays, but does not
>> reject messages. It will try the same behaviour as before. It will just
>> inform the user that somethings is tried which may not work. I probably
>> should update the error message printed saying that the transfer is
>> still tried.
> 
> Indeed, now I'm recalling noticing that the transfer actually should
> happen despite of the error message, but then completely forgot to
> update the commit's message. I can update the message and send out v5,
> if you're thinking that it's worthwhile to do.

I have time to do it now, will send v5 shortly.

And yes, clarifying the error message could be helpful. Although,
perhaps it won't help much to drivers which may schedule during the
atomic transfer.

>>> There were several occurrences where I found my Nexus 7 completely
>>> discharged despite of being turned off and then one day I spotted this in
>>> the log:
>>
>> Given my reasoning above, that should have happened before the warning
>> was printed as well? Because same behaviour. I'd be surprised if there
>> was a change...
> 
> Pretty sure that it was happening before, but I wasn't paying much
> attention back then.
>