DT include files (was: [GIT PULL 2/2] ARM: imx: device tree changes for 3.14)

[Shawn Guo]

Hi Olof,

On Thu, Jan 02, 2014 at 12:21:08PM -0800, Olof Johansson wrote:
> >  .../devicetree/bindings/vendor-prefixes.txt        |    3 +
> >  arch/arm/boot/dts/imx25-pinfunc.h                  |  494 +++++++++++
> >  arch/arm/boot/dts/imx25-pingrp.h                   |   81 ++
> >  arch/arm/boot/dts/imx27-pinfunc.h                  |  526 +++++++++++
> >  arch/arm/boot/dts/imx27-pingrp.h                   |  151 ++++
> >  arch/arm/boot/dts/imx35-pingrp.h                   |  104 +++
> >  arch/arm/boot/dts/imx50-pinfunc.h                  |  923 ++++++++++++++++++++
> >  arch/arm/boot/dts/imx50-pingrp.h                   |  146 ++++
> >  arch/arm/boot/dts/imx51-pingrp.h                   |  249 ++++++
> >  arch/arm/boot/dts/imx53-pingrp.h                   |  352 ++++++++
> >  arch/arm/boot/dts/imx6dl-pinfunc.h                 |    2 +
> >  arch/arm/boot/dts/imx6q-pinfunc.h                  |    2 +
> >  arch/arm/boot/dts/imx6qdl-pingrp.h                 |  532 +++++++++++
> >  arch/arm/boot/dts/imx6sl-pingrp.h                  |  148 ++++
> >  arch/arm/boot/dts/vf610-pingrp.h                   |  127 +++
> 
> Hm, these don't quite use include files the way include files were
> originally meant to be used -- initially the idea was to use them to
> define mostly simple constants instead of full properties like this.

The DT macro support was introduced to improve the readability of device
tree sources by replacing those magic numbers with readable macros.  I
think the usage in imx pinctrl binding perfectly fits the purpose.  You
can get details of the binding in
Documentation/devicetree/bindings/pinctrl/fsl,imx-pinctrl.txt.

> 
> I'm not against the idea of using it this way, but I also want to make sure the
> DT maintainers are OK with it. So I've cc:d them on this reply.

This is not a new thing. It was firstly adopted for imx6q in v3.10
release with commit e164153 (pinctrl: imx: move hard-coding data into
device tree), which had been posted to devicetree list for sure.  We're
just moving more i.MX SoCs to it.

> 
> I'm also not crazy about the insanely long identifiers used here, but I guess
> they correlate with some user manual tables?

Yes, the identifiers follows the pad and function names from reference
manual.

Shawn