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

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Message-ID: <20200728094720.x6pucwxsfwvz6nvv@pengutronix.de>
Date:   Tue, 28 Jul 2020 11:47:20 +0200
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Michael Walle <michael@...le.cc>
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>,
        Lee Jones <lee.jones@...aro.org>,
        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

Hallo,

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.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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