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

From: Lee Jones <lee.jones@linaro.org>
To: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
Cc: Michael Walle <michael@walle.cc>,
	linux-gpio@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-hwmon@vger.kernel.org,
	linux-pwm@vger.kernel.org, linux-watchdog@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	Linus Walleij <linus.walleij@linaro.org>,
	Bartosz Golaszewski <bgolaszewski@baylibre.com>,
	Rob Herring <robh+dt@kernel.org>,
	Jean Delvare <jdelvare@suse.com>,
	Guenter Roeck <linux@roeck-us.net>,
	Thierry Reding <thierry.reding@gmail.com>,
	Wim Van Sebroeck <wim@linux-watchdog.org>,
	Shawn Guo <shawnguo@kernel.org>, Li Yang <leoyang.li@nxp.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Jason Cooper <jason@lakedaemon.net>,
	Marc Zyngier <maz@kernel.org>, Mark Brown <broonie@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>, Pavel Machek <pavel@ucw.cz>
Subject: Re: [PATCH v6 06/13] pwm: add support for sl28cpld PWM controller
Date: Tue, 28 Jul 2020 11:51:21 +0100	[thread overview]
Message-ID: <20200728105121.GG2419169@dell> (raw)
In-Reply-To: <20200728094720.x6pucwxsfwvz6nvv@pengutronix.de>

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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