linux-kernel - Re: [RFC PATCH v2 4/4] mmc: sdhci-esdhc-imx: using pinmux subsystem

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Date:	Thu, 15 Dec 2011 19:21:45 +0800
From:	Shawn Guo <shawn.guo@...escale.com>
To:	Sascha Hauer <s.hauer@...gutronix.de>
CC:	Dong Aisheng-B29396 <B29396@...escale.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Guo Shawn-R65073 <r65073@...escale.com>,
	"linus.walleij@...ricsson.com" <linus.walleij@...ricsson.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	"grant.likely@...retlab.ca" <grant.likely@...retlab.ca>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"kernel@...gutronix.de" <kernel@...gutronix.de>
Subject: Re: [RFC PATCH v2 4/4] mmc: sdhci-esdhc-imx: using pinmux subsystem

On Thu, Dec 15, 2011 at 10:33:19AM +0100, Sascha Hauer wrote:
> On Thu, Dec 15, 2011 at 08:59:28AM +0000, Dong Aisheng-B29396 wrote:
> > > -----Original Message-----
> > > From: Linus Walleij [mailto:linus.walleij@...aro.org]
> > > Sent: Thursday, December 15, 2011 4:27 PM
> > > To: Guo Shawn-R65073
> > > Cc: Sascha Hauer; Dong Aisheng-B29396; linus.walleij@...ricsson.com;
> > > linux-kernel@...r.kernel.org; rob.herring@...xeda.com;
> > > grant.likely@...retlab.ca; linux-arm-kernel@...ts.infradead.org;
> > > kernel@...gutronix.de
> > > Subject: Re: [RFC PATCH v2 4/4] mmc: sdhci-esdhc-imx: using pinmux
> > > subsystem
> > > Importance: High
> > > 
> > > On Thu, Dec 15, 2011 at 8:05 AM, Shawn Guo <shawn.guo@...escale.com>
> > > wrote:
> > > >[Me]
> > > >> So if you want to do this for i.MX you need something like selectable
> > > >> dummy pinmuxes, i.e. pinmux_get() to return something that just say
> > > >> "OK" to everything like the dummy regulators.
> > > >>
> > > >> Shall I try to create something like that?
> > > >>
> > > > Isn't the empty functions defined in include/linux/pinctrl/pinmux.h
> > > > for this purpose?
> > > 
> > > No, these are for compiling it *out*, dummy pinmuxes would be if you
> > > compile it *in*, but don't find an apropriate pinmux, you still get
> > > something that does nothing and still works.
> > > 
> > > Dummy regulators work exactly this way.
> > > 
> > 
> > I did not read the dummy regulator code too much.
> > But does it mean that the dummy regulator or dummy pinmux will also hide the
> > Real errors since it will always get a available one?

What do you mean 'real error'?  When driver calls pimnux api on a
platform with real pinmux support, the error is error.  When driver
calls pinmux api on a platform support with dummy pinmux, it's totally
error free, as the pinmux core will ensure all the pinmux_* calls
always return success.

> > How do we distinguish between the two case(real error and fake error)?
> 
What do we need to distinguish between two cases?  The real success for
real pinmux from the fake success for the dummy pinmux?  It does not
really matter.

> We don't :(
> 
> That's the problem with the dummy regulator.
> 
What is the problem exactly?  I do not quite understand.

-- 
Regards,
Shawn

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