linux-kernel - RE: [PATCH 08/20] pinctrl: Assume map table entries can't have a NULL name field

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Date:	Thu, 23 Feb 2012 08:39:58 -0800
From:	Stephen Warren <swarren@...dia.com>
To:	Dong Aisheng <aisheng.dong@...escale.com>
CC:	Linus Walleij <linus.walleij@...aro.org>,
	Linus Walleij <linus.walleij@...ricsson.com>,
	"B29396@...escale.com" <B29396@...escale.com>,
	"s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
	"dongas86@...il.com" <dongas86@...il.com>,
	"shawn.guo@...aro.org" <shawn.guo@...aro.org>,
	"thomas.abraham@...aro.org" <thomas.abraham@...aro.org>,
	"tony@...mide.com" <tony@...mide.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 08/20] pinctrl: Assume map table entries can't have a
 NULL name field

Dong Aisheng wrote at Wednesday, February 22, 2012 9:48 PM:
> On Wed, Feb 22, 2012 at 07:53:44PM -0800, Stephen Warren wrote:
...
> > I'm hoping that we don't do this internal conversion. The rules I'd like are:
...
> > * Every mapping table entry must include a non-NULL name field.
> >
> > * Every call to pinctrl_get()/pinctrl_lookup_state() must pass a non-NULL name
>
> This is a way.
> 
> Before using this, i'm  still wondering what big problems do you think for us to support
> a NULL map name?
> Because the name for devices do not have different state really does not make too much
> sense but extra overhead.

If we disallow NULL names, it simplifies the code in the pinctrl core;
when registering mappings or right at the start of pinctrl_get() or
pinctrl_lookup_state(), we check if the name is NULL and if so error out.
Everywhere else can then assume name!=NULL, and hence not have special-
cases for name==NULL, e.g.:

In debug code:
name ? name : "(unnamed)"
vs.:
name

When matching mapping table entries:
match = !name ? !map->name : !strcmp(name, map->name)
vs.:
match = !strcmp(name, map->name)

Similar for the body of pinctrl_lookup_state().

Equally, it's not possible to generate a mapping table entry with a NULL
name from device tree given the bindings we discussed, so disallowing them
everywhere keeps things consistent.

-- 
nvpublic

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