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

[Stephen Warren]

Stephen Warren wrote at Thursday, January 12, 2012 1:47 PM:
> Shawn Guo wrote at Wednesday, January 11, 2012 8:40 PM:
> > On Wed, Jan 11, 2012 at 10:17:40AM -0800, Stephen Warren wrote:
> ...
> > > So, my position is that:
> > >
> > > * Something (either the pinctrl driver, or the SoC .dtsi file) should
> > > enumerate all available muxable entities that exist in the SoC (pins for
> > > IMX, groups for Tegra).
> >
> > Yes, we enumerate all available pins in pinctrl driver for imx.
> >
> > > * Something (either the pinctrl driver, or the SoC .dtsi file) should
> > > enumerate all the available functions that can be assigned to a muxable
> > > entity.
> >
> > In theory, yes.  But I hope you would agree we do not need to
> > necessarily do this for case like imx.
> 
> Discussing just the Linux driver internals right now; ignoring device
> tree:
> 
> Pinctrl won't let you use a function on a pin/group if that function
> isn't enumerated and doesn't list that pin/group as a valid location
> for that function. Given that, I'm not sure how you can avoid enumerating
> all functions and their legal locations?

Or you can cheat a little:

Define 8 functions named func0, func1, func2, ... func7. Tell pinctrl
that each function is a legal option on every pin. That way, you've
enumerated all the valid functions, and so satisfied pinctrl's error-
checking, yet kept a tiny list of functions. That'd have the bonus side-
effect that the function IDs map very directly to what I assume is in
your HW manuals too!

I wonder if I shouldn't have done that for Tegra. The main reason I didn't
is because the old Tegra pinmux driver didn't.

-- 
nvpublic