linux-kernel - Re: [PATCH RFC 02/11 v4] gpio: Add sysfs support to block GPIO API

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Date:	Tue, 16 Oct 2012 23:08:51 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	Roland Stigge <stigge@...com.de>, grant.likely@...retlab.ca,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	w.sang@...gutronix.de, jbe@...gutronix.de, plagnioj@...osoft.com,
	highguy@...il.com, broonie@...nsource.wolfsonmicro.com,
	daniel-gl@....net, rmallon@...il.com
Subject: Re: [PATCH RFC 02/11 v4] gpio: Add sysfs support to block GPIO API

On Tue, Oct 16, 2012 at 7:40 PM, Greg KH <gregkh@...uxfoundation.org> wrote:
> On Tue, Oct 16, 2012 at 07:27:15PM +0200, Linus Walleij wrote:
>> The thing is, as I've tried to explain but maybe didn't get across,
>> that these devices don't *have* a parent, and are not part of any
>> tree.
>
> You are passing in a parent device to the device_create() call, where
> did that pointer come from?

You mean this:

dev = device_create(&gpio_class, desc->chip->dev, MKDEV(0, 0),
                        desc, ioname ? ioname : "gpio%u", gpio);

desc->chip->dev is an *optional* pointer to a parent device of
the GPIO chip (not the GPIO chip itself). It is usually NULL.

>> They are parentless mock devices, created on-the-fly just to get
>> sysfs entries.
>
> That's fine, well, not the "parentless" part, but that should be trivial
> to fix, just pass in the correct pointer and you should be fine.

Hm, yeah well, they are orphans mostly.

>> What is needed it to get the device model right in the first
>> place.
>
> I thought it was in the device model already?

GPIO chips are not devices. :-(

Yours,
Linus Walleij
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