Re: [PATCH v3 1/3] mfd: mc13xxx: add device tree probe support

[Mark Brown <broonie@opensource.wolfsonmicro.com>]

On Wed, Dec 21, 2011 at 09:25:21AM +0800, Shawn Guo wrote:
> On Tue, Dec 20, 2011 at 11:25:27PM +0000, Mark Brown wrote:

> > It's unique but I feel the disadvantages in terms of legibility of the
> > resulting device trees are substantial - we want humans to be able to
> > read and write device trees, preferrably without having to dig out the
> > datasheet for the part.

> Eh, device tree is all about describing hardware.  I do not understand
> what is wrong with looking at hardware manual when writing dts.

For the same reason we define constants for register names and values
when writing drivers - so humans can make sense of what's in front of
them and to reduce the chance of errors when things are being written.

> > So long as the names are reasonably sensible
> > and can be understood in the case of any lack of clarity we should be
> > OK.

> The problem is even if we have the name defined that way, it has to be
> matched to the name used in mc13892 driver somehow, if we want to use
> name as the key to find the regulator defined in mc13892 driver as
> array mc13892_regulators[].

This doesn't seem like a problem - the most obvious thing would just be
to adjust the strings in the code to correspond to what the device tree
binding says.

> > This is the whole reason why I'm saying that you need to define the
> > names used in the binding - if the names are a defined part of the
> > binding then there's nothing driver specific about them.

> Can you please help me understand how this can be achieved with an
> example?  Taking 'mc13892__sw1' as the example, if I read your comment
> before correctly, 'sw1' is the name that you are suggesting.  How this
> name can be nothing driver specific?  After all, we need to find
> regulator MC13892_SW1 defined in mc13892_regulators[] by matching name
> 'sw1' defined by binding and name 'MC13892_SW1' defined by driver
> somehow, if we want to use name to bind the regulator.

Your binding document would say something like "the regulators are bound
using their names as listed below with their enable bits:

  sw1 - SW1 regulator (register X bit Y)

" so in the binding document it would say what strings map onto which
regulators.  Then any driver implementing that binding would pick the
same strings.