-----Original Message-----
From: Guo Shawn-R65073
Sent: Thursday, December 15, 2011 7:22 PM
To: Sascha Hauer
Cc: Dong Aisheng-B29396; Linus Walleij; Guo Shawn-R65073;
linus.walleij at stericsson.com; linux-kernel at vger.kernel.org;
rob.herring at calxeda.com; grant.likely at secretlab.ca; linux-arm-
kernel at lists.infradead.org; kernel at pengutronix.de
Subject: Re: [RFC PATCH v2 4/4] mmc: sdhci-esdhc-imx: using pinmux
subsystem
Importance: High

On Thu, Dec 15, 2011 at 10:33:19AM +0100, Sascha Hauer wrote:

quoted

On Thu, Dec 15, 2011 at 08:59:28AM +0000, Dong Aisheng-B29396 wrote:

quoted

quoted

-----Original Message-----
From: Linus Walleij [mailto:linus.walleij at linaro.org]
Sent: Thursday, December 15, 2011 4:27 PM
To: Guo Shawn-R65073
Cc: Sascha Hauer; Dong Aisheng-B29396;
linus.walleij at stericsson.com; linux-kernel at vger.kernel.org;
rob.herring at calxeda.com; grant.likely at secretlab.ca;
linux-arm-kernel at lists.infradead.org;
kernel at pengutronix.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
[off-list ref]
wrote:

quoted

[Me]

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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.

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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.

My understanding is that pinmux_get will return an error if no proper pinmux
Found without dummy pinmux. That's a real error.
But with dummy pinmux, if no proper pinmux found, the pinctrl core may check
If dummy pinmux is supported, if supported, it will fakely success with returning
a dummy pinmux. Then real error is hiden.
This is due to for supporting one single image, the dummy pinmux may also be enabled
For platforms like mx6q with real pinmux.

I just did a quick look at the regulator code and got this understanding,
please let me know if I understood wrong.

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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.

quoted

We don't :(

That's the problem with the dummy regulator.

What is the problem exactly?  I do not quite understand.

--
Regards,
Shawn