linux-kernel - Re: [PATCH v6 06/13] pwm: add support for sl28cpld PWM controller

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Date:   Tue, 28 Jul 2020 11:51:21 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
Cc:     Michael Walle <michael@...le.cc>, linux-gpio@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hwmon@...r.kernel.org, linux-pwm@...r.kernel.org,
        linux-watchdog@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Rob Herring <robh+dt@...nel.org>,
        Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Thierry Reding <thierry.reding@...il.com>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Shawn Guo <shawnguo@...nel.org>, Li Yang <leoyang.li@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Marc Zyngier <maz@...nel.org>, Mark Brown <broonie@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Pavel Machek <pavel@....cz>
Subject: Re: [PATCH v6 06/13] pwm: add support for sl28cpld PWM controller

On Tue, 28 Jul 2020, Uwe Kleine-König wrote:
> On Tue, Jul 28, 2020 at 10:21:22AM +0200, Michael Walle wrote:
> > Am 2020-07-28 09:43, schrieb Uwe Kleine-König:
> > > On Sun, Jul 26, 2020 at 01:18:27AM +0200, Michael Walle wrote:
> > > > +static int sl28cpld_pwm_probe(struct platform_device *pdev)
> > > > +{
> > > > +	struct sl28cpld_pwm *priv;
> > > > +	struct pwm_chip *chip;
> > > > +	int ret;
> > > > +
> > > > +	if (!pdev->dev.parent)
> > > > +		return -ENODEV;
> > > > +
> > > > +	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
> > > > +	if (!priv)
> > > > +		return -ENOMEM;
> > > > +
> > > > +	priv->regmap = dev_get_regmap(pdev->dev.parent, NULL);
> > > > +	if (!priv->regmap)
> > > 
> > > Error message here?
> > 
> > This shouldn't really happen and I put it into the same category
> > as the two above and report no error. But I can add it.
> 
> For kzalloc it is right to not emit an error because a failing kzalloc
> is already loud on its own. I missed the first error path, that should
> get a message, too.
> 
> > Generally, it looked to me that more and more drivers don't
> > really report errors anymore, but just return with an -EWHATEVER.
> > So if someone can shed some light here, I'm all ears.
> 
> IMHO it's wrong not to add error messages. At one point in time it will
> fail and then you're happy if you don't have to add printks all over the
> place first to debug that.

Error messages should only be omitted for -ENOMEM and if something is
already being printed out, ideally by the sub-system API.

-- 
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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