linux-kernel - Re: [PATCH 1/2] gpio: pl061: get gpio base from alias id

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Date:	Fri, 25 Apr 2014 11:29:49 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Haojian Zhuang <haojian.zhuang@...aro.org>
Cc:	Grant Likely <grant.likely@...aro.org>,
	Xu Wei <xuwei5@...ilicon.com>,
	Rob Herring <robh+dt@...nel.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Baruch Siach <baruch@...s.co.il>
Subject: Re: [PATCH 1/2] gpio: pl061: get gpio base from alias id

On Fri, Apr 25, 2014 at 2:27 AM, Haojian Zhuang
<haojian.zhuang@...aro.org> wrote:

> Go it. But the gpio sysfs interface is using the gpio name with an
> internal number. It'll make developer confusion since it's different
> from datasheet
> or schematics. Is there any plan to remove the confusion?

First I am as always very suspicious about the sysfs interface
since it is often used for madness like reimplementing
leds-gpio.c, gpio_keys.c, extcon-gpio.c, gpio-regulator.c
spi-gpio.c, w1-gpio.c or gpio_wdt.c in userspace for no
good reason when the kernel should handle it.

Yet there are exceptions where it's actually warranted.

There is a possibility to set a label on the gpio line,
so this should be used.

C.f.
commit 781f6d710d4482eab05cfaad50060a0ea8c0e4e0
"gpio: generic: Add label to platform data"

Something like this is needed in this and other drivers
needing to label its GPIO lines. It's much like how we name
all pins in a pin controller really.

I don't exactly know how we should achieve the same
for labels to offsets in any given gpio_chip using
some generic device tree labels for example, but I
imagine it could be implemented in a generic fashion?

Describing the names of gpio lines should be quite
obvious hardware description suitable for the device
tree.

Yours,
Linus Walleij
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