linux-kernel - Re: [PATCH v5] i2c: imx: make bus recovery through pinctrl optional

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Message-ID: <CADRPPNQbTCs9TLqUSNUTG6YBn3fs8F6FKUw1G582D4ExcL1oVQ@mail.gmail.com>
Date:   Mon, 12 Sep 2016 11:27:13 -0500
From:   Leo Li <pku.leo@...il.com>
To:     Lothar Waßmann <LW@...o-electronics.de>
Cc:     Stefan Agner <stefan@...er.ch>, Gao Pan <pandy.gao@....com>,
        Wolfram Sang <wsa@...-dreams.de>,
        lkml <linux-kernel@...r.kernel.org>,
        Li Yang <leoyang.li@....com>, linux-gpio@...r.kernel.org,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v5] i2c: imx: make bus recovery through pinctrl optional

On Mon, Sep 12, 2016 at 3:21 AM, Lothar Waßmann <LW@...o-electronics.de> wrote:
> Hi,
>
> On Fri, 9 Sep 2016 14:37:12 -0500 Leo Li wrote:
>> On Fri, Sep 9, 2016 at 11:51 AM, Stefan Agner <stefan@...er.ch> wrote:
>> > On 2016-09-08 16:57, Leo Li wrote:
> [...]
>> >> people fix problem that they don't really care by deliberately enlarge
>> >> the problem.  That's why we don't panic() on any error we found.  For
>> >> those who do care about the bus recovery, they can get the information
>> >> from the console.
>> >
>> > IMHO, it is just stupid to ignore errors and then let the developer
>> > later on trace back what the initial issue was. Error out early is a
>> > common sense software design principle...
>> >
>> > I am not asking for a panic(), I am just suggesting to only ignore
>> > pinctrl if it returns -ENODEV, the case you care are about.
>>
>> It was just an analogy for enlarging the problem for getting
>> attention.  But you probably thought that it was not enlarging the
>> problem as you think pinctrl is required by the driver instead of an
>> optional thing.
>>
> The I2C bus recovery is a feature which is not used during normal
> operation and you won't find that it's not working unless something
> unusual happens (probably only in a productive environment). It may even
> be hard to trigger a condition to test the feature.
> Thus IMO it is vital that the driver complains loudly if something is
> missing to make this feature work if requested.

I agree.  A message is already added in this patch to mention that bus
recovery is not supported due to pinctrl when there is a problem.

Regards,
Leo