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

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Message-ID: <20170726082304.7j4lbvsuyyu7owqy@dell>
Date:   Wed, 26 Jul 2017 09:23:04 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
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 Tue, 25 Jul 2017, Andy Shevchenko wrote:

> On Tue, Jul 25, 2017 at 12:10 PM, Lee Jones <lee.jones@...aro.org> wrote:
> > On Fri, 21 Jul 2017, Mani, Rajmohan wrote:
> >> > On Wed, 19 Jul 2017, Rajmohan Mani wrote:
> 
> >> > > + /* Force software reset */
> >> > > + ret = regmap_write(regmap, TPS68470_REG_RESET,
> >> > TPS68470_REG_RESET_MASK);
> >> > > + if (ret < 0)
> >> >
> >> > Will 'if (!ret)' do?
> >> >
> >>
> >> We intend to check error conditions and bail out. So, if (ret < 0) works for this.
> >
> > Yes, 'if (!ret)' does that too.
> 
> Did you mean
> 
> if (ret)
>  return ret;
> 
> ?

Yes, I just noticed!

Apologies for the confusion.

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

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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