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

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Message-ID: <20120113035506.GB12184@S2101-09.ap.freescale.net>
Date:	Fri, 13 Jan 2012 11:55:08 +0800
From:	Shawn Guo <shawn.guo@...aro.org>
To:	Stephen Warren <swarren@...dia.com>
Cc:	Dong Aisheng-B29396 <B29396@...escale.com>,
	Dong Aisheng <dongas86@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linus.walleij@...ricsson.com" <linus.walleij@...ricsson.com>,
	"s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"kernel@...gutronix.de" <kernel@...gutronix.de>,
	"cjb@...top.org" <cjb@...top.org>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	"Simon Glass (sjg@...omium.org)" <sjg@...omium.org>
Subject: Re: [RFC PATCH v3 2/5] pinctrl: add dt binding support for pinmux
 mappings

On Thu, Jan 12, 2012 at 12:56:52PM -0800, Stephen Warren wrote:
> Dong Aisheng wrote at Thursday, January 12, 2012 1:36 AM:
> > Stephen Warren wrote at Thursday, January 12, 2012 4:18 AM:
> > > Dong Aisheng wrote at Tuesday, January 10, 2012 1:21 AM:
> > > > Stephen Warren wrote at Saturday, January 07, 2012 2:03 AM:
> ...
> > > Personally, I think I'd be OK with the sysfs pinctrl map file only containing
> > > the map entries for devices that had used the pinctrl API, and hence only
> > > parsing the pinmux properties in pinmux_get().
> >
> > Actually I already did it like that in the patch I sent:
> > https://lkml.org/lkml/2012/1/5/153
> > 
> > Originally I'd like to do like that but I found an inconsistent issue that
> > the sysfs pinctrl map file will behave differently between dt and non-dt
> > Platform. For non-dt, it means showing all exist map entries. For dt, it means
> > Only used pinmux map entries.
> > 
> > And in current design when device calls pinmux_get, it will search a predefined
> > pinmux_maps array to find which function and group it is binded to.
> > If switch to the new way, we only dynamically create pinmux map and dynamically
> > register it when pinmux_get is called, first we need to change the code path in
> > pinmux_get in a totally different way, second for support that we may also better
> > to change pinmux_maps array to a list.
> > But after changing the pinmux_maps to a list, what about using in non-dt?
> > 
> > So without any strong reason i still think it would be better to keep consistency
> > With the non-dt pinctrl subsystem.
> > And the effort would be minimum since besides constructing the map by parsing
> > Device tree, everyting is the same as before in pinmux map and we could re-use
> > the current code.
> 
> OK. I think this can work out pretty easily with a bus notifier as I
> mentioned before.
> 
> But, one thought on doing this in pinmux_get(). I'd simply implement a
> Function that read a DT node's pinmux property/node, converted it to a
> pinmux mapping table, and registered it with the pinctrl core. Then,
> pinmux_get() could simply call this before doing anything else at all.
> I don't think you'd need to modify how pinmux_get() worked at all.
> 
This sounds like a pretty good idea to me.

-- 
Regards,
Shawn
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