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

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Date:	Wed, 22 Feb 2012 14:21:02 +0800
From:	Dong Aisheng <aisheng.dong@...escale.com>
To:	Stephen Warren <swarren@...dia.com>
CC:	Dong Aisheng <dongas86@...il.com>,
	Linus Walleij <linus.walleij@...ricsson.com>,
	"B29396@...escale.com" <B29396@...escale.com>,
	"s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
	"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

On Tue, Feb 21, 2012 at 09:38:47AM -0800, Stephen Warren wrote:
> Dong Aisheng wrote at Tuesday, February 21, 2012 6:08 AM:
> > On Mon, Feb 20, 2012 at 2:45 PM, Stephen Warren <swarren@...dia.com> wrote:
> > > pinctrl_register_mappings() already requires that every mapping table
> > > entry have a non-NULL name field.
> > >
> > > Logically, this makes sense too; drivers should always request a specific
> > > named state so they know what they're getting. Relying on getting the
> >
> > Hmm? It makes me a little confused.
> > IIRC we allow the driver to request NULL map name in the linaro
> > connect discussion.
> > For those devices they do not want to support multi states, they
> > really don't want to care about the state name.
> > The original way is convenient for such a case.
> 
> With device tree, every state is always going to have /some/ name; the
I remember the discussion is that pinctrl-name is optional and map name
is always specified by pinctrl-name or automatically generated by the id
of pinctrl property (e.g. for pinctrl-0, 0 is the name)
However user may not want to care about it although there's a name.

BTW my above comment may not right since i still have not read all you patches
in the series and do not know if any difference on your implementation with
the original proposal i will continue to read your patches.

> binding we discussed didn't include any way to specify "no name" or
> "default name" or "default state", so this will keeps things a little
> more consistent.
> 
> I possibly could be persuaded to allow NULL state names in the mapping
> table. However, if so, I think they should work a little differently to
> the code currently in pinctrl: Right now, a NULL parameter to pinmux_get()
> allows matching against /any/ state name in the table. If we changed this
Yes it's /any/ state but it's always the first state.

> to only allow matching against mapping table with a NULL name, that might
> be OK, since it'd be very explicit what it matched. But, as I mentione
If that how about many states with NULL name?

> above, migrating such a driver to device tree would require changing this
I can see many changes, it looks just as the same as before (using first
state as default state), did i understand right?

> so I'm not inclined to like that solution without strong requirements.
> 
> In other words, what we have right now is something like:
> 
> if name:
>     match = !strcmp(name, map->name)
> else:
>     match = true
> 
> If we continue to allow NULL names, I think we should change that to:
> 
> if name:
>     match = map->name && !strcmp(name, map->name)
> else:
>     match = !map->name
As above many states name may be NULL.
So here it becomes the first NULL name state.

Regards
Dong Aisheng

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