linux-kernel - Re: [PATCH v4 1/3] mfd: Add new mfd device TPS68470

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Date:   Wed, 26 Jul 2017 13:26:30 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     "Mani, Rajmohan" <rajmohan.mani@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Alexandre Courbot <gnurou@...il.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        "sakari.ailus@...ux.intel.com" <sakari.ailus@...ux.intel.com>
Subject: Re: [PATCH v4 1/3] mfd: Add new mfd device TPS68470

On Wed, Jul 26, 2017 at 11:23 AM, Lee Jones <lee.jones@...aro.org> wrote:
> On Tue, 25 Jul 2017, Andy Shevchenko wrote:
>> On Tue, Jul 25, 2017 at 12:10 PM, Lee Jones <lee.jones@...aro.org> wrote:

>> I briefly checked few ->read() and ->write() implementations and
>> didn't find any evidence of positive numbers that can be returned.
>> Documentation (kernel doc) doesn't shed a light on that. So, to me it
>> sounds unspecified.
>>
>> So, for now (until documentation will be fixed) I would rely on
>> if (ret < 0)
>
> It's not unspecified.  The regmap methods call into regcache_write(),
> where the kerneldoc is clear.

drivers/base/regmap/regcache.c:266

" * Return a negative value on failure, 0 on success."

I can hardly find this any cleaner than "unspecified".

>  Perhaps we can also change the regmap
> kerneldoc headers too to match, which might lessen the disparity.

I'm not familiar with the guts of regmap API, so, I would stick with
if (ret < 0) for now until documentation specifies positive return values.

-- 
With Best Regards,
Andy Shevchenko