linux-kernel - Re: [PATCH v5 2/3] mfd: qcom-rpm: Driver for the Qualcomm RPM

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Date:	Fri, 22 Aug 2014 08:50:41 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Bjorn Andersson <bjorn.andersson@...ymobile.com>
Cc:	Rob Herring <robh+dt@...nel.org>, Mark Brown <broonie@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Andy Gross <agross@...eaurora.org>,
	Mark Rutland <mark.rutland@....com>,
	Kevin Hilman <khilman@...aro.org>,
	Kumar Gala <galak@...eaurora.org>,
	Josh Cartwright <joshc@...eaurora.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH v5 2/3] mfd: qcom-rpm: Driver for the Qualcomm RPM

On Thu, 21 Aug 2014, Bjorn Andersson wrote:
> On Thu 21 Aug 06:22 PDT 2014, Lee Jones wrote:
> > > +struct qcom_rpm *dev_get_qcom_rpm(struct device *dev)
> > > +{
> > > +	return dev_get_drvdata(dev);
> > > +}
> > > +EXPORT_SYMBOL(dev_get_qcom_rpm);
> > 
> > No need for this at all.  Use dev_get_drvdata() direct instead.
> > 
> 
> I see that others have put this as static inline in the header file, so I will
> follow that. I don't want to expose this directly in the implementation of the
> clients.
> 
> Let me know if you object.

I do (unless you convince me otherwise).  Why is this a good idea and
why 'exposing' this directly is a bad one?  At the moment this looks
to me like abstraction for the sake of abstraction.

> > > +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > > +	rpm->status_regs = devm_ioremap_resource(&pdev->dev, res);
> > > +	rpm->ctrl_regs = rpm->status_regs + 0x400;
> > > +	rpm->req_regs = rpm->status_regs + 0x600;
> > > +	if (IS_ERR(rpm->status_regs))
> > > +		return PTR_ERR(rpm->status_regs);
> > 
> > You should probably do this _before_ using it above.
> 
> There's no difference in behaviour, but it just feels cleaner than:
> 
> res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> rpm->status_regs = devm_ioremap_resource(&pdev->dev, res);
> if (IS_ERR(rpm->status_regs))
> 	return PTR_ERR(rpm->status_regs);
> rpm->ctrl_regs = rpm->status_regs + 0x400;
> rpm->req_regs = rpm->status_regs + 0x600;
> 
> If you don't like it, I'll change it.

There is a difference.  In the current implementation you're doing math
with a possible error code and assigning rubbish to rpm->ctrl_regs and
rpm->req_regs.

[...]

> > > +MODULE_DESCRIPTION("Qualcomm Resource Power Manager driver");
> > > +MODULE_LICENSE("GPL v2");
> > 
> > No one authored this driver?
> > 
> 
> Thought that was optional, will update.

It's also helpful.  Can you place an Author: line in the header(s) too.

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