[PATCH v3] docs: dt-bindings: add DTS Coding Style document

[Andrew Lunn]

On Sun, Nov 26, 2023 at 11:38:38AM +0100, Krzysztof Kozlowski wrote:
> On 25/11/2023 20:47, Andrew Lunn wrote:
> >> +=====================================
> >> +Devicetree Sources (DTS) Coding Style
> >> +=====================================
> >> +
> >> +When writing Devicetree Sources (DTS) please observe below guidelines.  They
> >> +should be considered complementary to any rules expressed already in Devicetree
> >> +Specification and dtc compiler (including W=1 and W=2 builds).
> >> +
> >> +Individual architectures and sub-architectures can add additional rules, making
> >> +the style stricter.
> > 
> > It would be nice to add a pointer where such rules are documented.
> 
> Subsystem profile or any other place. The generic doc should not point
> to specific ones.

That is not so friendly for a developer. A reviewer points out that a
file is not consistent with the coding style. So they go away and fix
it, as described here. They then get a second review which say, no,
you to do X, Y and Z, despite them actually following the coding
style.

Maybe add to the paragraph above:

These further restrictions are voluntary, until added to this
document.

This should encourage those architectures to document their coding
style.

> The root node is a bit special, but other than that mixing nodes with
> and without unit address is discouraged practice.

If the root node is special, maybe it needs a few rules of its own?
All properties without an address come first, then properties with
addresses. Sorting within these classes follow the normal rules
already stated?

> >> +Indentation
> >> +-----------
> >> +
> >> +1. Use indentation according to :ref:`codingstyle`.
> >> +2. For arrays spanning across lines, it is preferred to align the continued
> >> +   entries with opening < from the first line.
> >> +3. Each entry in arrays with multiple cells (e.g. "reg" with two IO addresses)
> >> +   shall be enclosed in <>.
> >> +
> >> +Example::
> >> +
> >> +	thermal-sensor at c271000 {
> >> +		compatible = "qcom,sm8550-tsens", "qcom,tsens-v2";
> >> +		reg = <0x0 0x0c271000 0x0 0x1000>,
> >> +		      <0x0 0x0c222000 0x0 0x1000>;
> >> +	};
> > 
> > I'm not sure i understand this. Is this example correct?
> > 
> >                 gpio-fan,speed-map = <0    0
> >                                       3000 1
> >                                       6000 2>;
> > 
> > It exists a lot in todays files.
> 
> Depends on the binidng. Is it matrix? If yes, then it is not correct.

It seems to me, rules 2 and 3 should be swapped. You can only align
the <, if you have <. So logically, the rule about having < should
come first.

     Andrew