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

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Date:	Thu, 12 Jan 2012 12:56:52 -0800
From:	Stephen Warren <swarren@...dia.com>
To:	Dong Aisheng-B29396 <B29396@...escale.com>,
	Dong Aisheng <dongas86@...il.com>
CC:	"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

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.

-- 
nvpublic

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