linux-kernel - Re: [RFC PATCH v3 2/5] pinctrl: add dt binding support for pinmux mappings

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Message-ID: <20120117023206.GA11756@S2101-09.ap.freescale.net>
Date:	Tue, 17 Jan 2012 10:32:11 +0800
From:	Shawn Guo <shawn.guo@...aro.org>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	Stephen Warren <swarren@...dia.com>,
	"linus.walleij@...ricsson.com" <linus.walleij@...ricsson.com>,
	"s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	Richard Zhao <richard.zhao@...aro.org>,
	"kernel@...gutronix.de" <kernel@...gutronix.de>,
	"cjb@...top.org" <cjb@...top.org>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Dong Aisheng <dongas86@...il.com>
Subject: Re: [RFC PATCH v3 2/5] pinctrl: add dt binding support for pinmux
 mappings

On Mon, Jan 16, 2012 at 05:08:57PM +0100, Linus Walleij wrote:
...
> As you can see none of the text above claims that the group is
> about hardware-defined groups or anything like that. The groups
> are just that - a group of pins, an abstract concept of a group.

Ok, the thing gets clarified.  The concept of group is a abstract at
software level.  It does not necessarily require a pin group defined
by raw hardware underneath, which is basically my argument.

> It could be drawn i UML even... maybe I'll do that for my
> ELC presentation :-)
> 
> Then when we come to pinmux, which is slightly different
> involving the definitions of a function and mappings between
> functions and one or more pin groups as per above, which is
> something completely different and seems to be what you're
> discussing here?
> 
> For hardware that does handle pins in groups there are
> special functions that can be used in the drivers like
> configuring a whole group (which falls back to iterating
> over pins if there is no such callback, showing again that
> this is a theoretical concept) so if the hardware handles
> pins in groups its a good idea to match group definitions
> 1-to-1 with these, but for hardware that doesn't there is
> some freedom of how to use the groups.
> 
> I don't know if this helps though the discussion here seems
> a bit contended :-/
> 
It does help to me.  Thanks, Linus.

-- 
Regards,
Shawn
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