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

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Date:	Fri, 13 Jan 2012 08:07:35 +0000
From:	Dong Aisheng-B29396 <B29396@...escale.com>
To:	Shawn Guo <shawn.guo@...aro.org>,
	Stephen Warren <swarren@...dia.com>
CC:	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

> -----Original Message-----
> From: Shawn Guo [mailto:shawn.guo@...aro.org]
> Sent: Friday, January 13, 2012 11:55 AM
> To: Stephen Warren
> Cc: Dong Aisheng-B29396; Dong Aisheng; linux-kernel@...r.kernel.org;
> linus.walleij@...ricsson.com; s.hauer@...gutronix.de; rob.herring@...xeda.com;
> linux-arm-kernel@...ts.infradead.org; kernel@...gutronix.de; cjb@...top.org;
> devicetree-discuss@...ts.ozlabs.org; Simon Glass (sjg@...omium.org)
> Subject: Re: [RFC PATCH v3 2/5] pinctrl: add dt binding support for pinmux
> mappings
> Importance: High
> 
> 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.
> >
Sorry I did not catch your idea before.
I will try to see if I can find an example.

> > 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.
> 
This does not fix the inconsistency issue.
Additionally as I said before, for better support dynamically register pinmux
Map, it looks we'd better change the pinmux_maps array to a list.
However this is for dt case.
But for non-dt case, the static array is just ok.
So there's conflict.
Not sure if any better idea to fix this.

Regards
Dong Aisheng

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