linux-kernel - Re: [PATCH v2 4/4] ARM: dts: mt8135: Add pinctrl node for mt8135.

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Date:	Wed, 24 Sep 2014 14:40:44 +0200
From:	Sascha Hauer <s.hauer@...gutronix.de>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	"Hongzhou.Yang" <srv_hongzhou.yang@...iatek.com>,
	Rob Herring <robh+dt@...nel.org>,
	Matthias Brugger <matthias.bgg@...il.com>,
	srv_heupstream@...iatek.com, Sascha Hauer <kernel@...gutronix.de>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Russell King <linux@....linux.org.uk>,
	Grant Likely <grant.likely@...aro.org>,
	Hongzhou Yang <hongzhou.yang@...iatek.com>,
	"Joe.C" <yingjoe.chen@...iatek.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Vladimir Murzin <vladimir.murzin@....com>,
	Ashwin Chaugule <ashwin.chaugule@...aro.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>, dandan.he@...iatek.com
Subject: Re: [PATCH v2 4/4] ARM: dts: mt8135: Add pinctrl node for mt8135.

Hi Linus,

On Wed, Sep 24, 2014 at 01:23:09PM +0200, Linus Walleij wrote:
> On Tue, Sep 23, 2014 at 5:39 AM, Hongzhou.Yang
> <srv_hongzhou.yang@...iatek.com> wrote:
> 
> > From: Hongzhou Yang <hongzhou.yang@...iatek.com>
> >
> > Add pinctrl node to mt8135.dtsi.
> >
> > Signed-off-by: Hongzhou Yang <hongzhou.yang@...iatek.com>
> (...)
> > +#define MT8135_PIN_0_MSDC0_DAT7__FUNC_GPIO0 (MT_PIN_NO(0) | 0)
> > +#define MT8135_PIN_0_MSDC0_DAT7__FUNC_MSDC0_DAT7 (MT_PIN_NO(0) | 1)
> > +#define MT8135_PIN_0_MSDC0_DAT7__FUNC_EINT49 (MT_PIN_NO(0) | 2)
> > +#define MT8135_PIN_0_MSDC0_DAT7__FUNC_I2SOUT_DAT (MT_PIN_NO(0) | 3)
> 
> I haven't got to reviewing the driver, but this looks just wrong.
> 
> Have the magic numbers in the driver.
> 
> Use strings to describe functions, not integers.

Interrupts, clocks, gpios, dma channels, nearly everything in the device tree is
arbitrarily numbered. Instead of "irq-i2c0" we have <0 36 IRQ_TYPE_LEVEL_HIGH>
in the device tree. These numbers can be resolved efficiently in the
driver by shifting them to get a bitmask or by adding them as offset to
a register base.
Why do you want to make pinctrl different? Thanks to the recently
introduced defines in the device trees these numbers are not magic at
all anymore.

> 
> We need to move toward standardized device tree bindings
> for this stuff, and that means using strings, not magic
> numbers.

Agreed for standardized device tree bindings, but not for using strings.

Sascha

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