linux-kernel - Re: [PATCH v3] i2c: imx: make bus recovery through pinctrl optional

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Date:	Mon, 18 Jan 2016 16:22:51 +0800
From:	Li Yang <leoli@...escale.com>
To:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
Cc:	Gao Pan <pandy.gao@....com>, Wolfram Sang <wsa@...-dreams.de>,
	Linus Walleij <linus.walleij@...aro.org>,
	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>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3] i2c: imx: make bus recovery through pinctrl optional

On Fri, Jan 15, 2016 at 5:03 PM, Uwe Kleine-König
<u.kleine-koenig@...gutronix.de> wrote:
> Hello Li,
>
> On Fri, Jan 15, 2016 at 04:46:06PM +0800, Li Yang wrote:
>> On Fri, Jan 15, 2016 at 3:53 PM, Uwe Kleine-König
>> <u.kleine-koenig@...gutronix.de> wrote:
>> >> -     i2c_imx_init_recovery_info(i2c_imx, pdev);
>> >> +     if (IS_ERR_OR_NULL(i2c_imx->pinctrl))
>> >
>> > I'd prefer to set i2c_imx->pinctrl to NULL if it's not used and then use
>> >
>> >         if (!i2c_imx->pinctrl)
>> >
>> > here. (Or maybe make i2c_imx_init_recovery_info aware of this situation
>> > to keep the caller simple?)
>>
>> Setting not used pointer to NULL might be a good coding practice
>> generally.  But in this case neither the driver nor gpio framework
>> checks if the pinctrl is NULL before accessing it.  We still need the
>> driver to make sure pinctrl is not used in this situation.  The
>> benefit of the proposed change seems to be pretty limited.  :)
>
> At least it gets rid of IS_ERR_OR_NULL which is used wrongly more often
> than not.

It's true that this API is not used a lot.  Are you suggesting that it
is poorly designed and probably should be removed?  But I still don't
quite get the point why it tends to be wrongly used.  Do you consider
the use in this patch a wrongly used case?

Regards,
Leo