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

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Message-ID: <20160912102136.04c0728d@ipc1.ka-ro>
Date:   Mon, 12 Sep 2016 10:21:36 +0200
From:   Lothar Waßmann <LW@...O-electronics.de>
To:     Leo Li <pku.leo@...il.com>
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

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.


Lothar Waßmann