linux-kernel - Re: [PATCH RFC 4/6] net: rfkill: gpio: add device tree support

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Message-Id: <201401211950.07011.arnd@arndb.de>
Date:	Tue, 21 Jan 2014 19:50:06 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Alexandre Courbot <gnurou@...il.com>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	netdev <netdev@...r.kernel.org>,
	"linux-wireless" <linux-wireless@...r.kernel.org>,
	"linux-sunxi" <linux-sunxi@...glegroups.com>,
	"linux-kernel" <linux-kernel@...r.kernel.org>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	"Chen-Yu Tsai" <wens@...e.org>,
	Johannes Berg <johannes@...solutions.net>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	"David S. Miller" <davem@...emloft.net>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>
Subject: Re: [PATCH RFC 4/6] net: rfkill: gpio: add device tree support

On Tuesday 21 January 2014, Alexandre Courbot wrote:
> >> As discussed earlier in this thread I'm not sure the con_id is
> >> suitable for labelling GPIOs. It'd be better to have a proper name
> >> specified in DT/ACPI instead.
> >
> > +1
> 
> I wonder why you guys prefer to have the name defined in the GPIO
> mapping. Having the driver decide the label makes it easier to look up
> which GPIO does what in debugfs, whereas nothing prevents people to
> name GPIOs whatever inadequate name they want in the device DT node.
> What am I overlooking here?

I should have another look at the debugfs representation, but isn't
there a global namespace that gets used for all gpios?  Neither the
con_id nor the name that the driver picks would be globally unique
and stable across kernel versions, so they don't make a good user
interface.

I think what we want here is a system-wide unique identifier for
each gpio line that may get represented in debugfs, and use a new
DT mechanism to communicate that.

	Arnd
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