Re: [PATCH 4/5] pwm: tegra: Add DT node compatible for Tegra186

[Stephen Warren]

On 06/24/2016 10:10 AM, Rob Herring wrote:
> On Wed, Jun 22, 2016 at 02:46:14PM +0200, Thierry Reding wrote:
> > On Wed, Jun 22, 2016 at 05:17:22PM +0530, Laxman Dewangan wrote:
> > > Tegra186 has 8 different PWM controller and each controller has only
> > > one output. Earlier generation SoCs have the 4 PWM output per controller.
> > >
> > > Add DT node compatible for Tegra186.
> > >
> > > Signed-off-by: Laxman Dewangan <ldewangan@xxxxxxxxxx>
> > > ---
> > >   Documentation/devicetree/bindings/pwm/nvidia,tegra20-pwm.txt | 10 ++++++----
> > >   1 file changed, 6 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/Documentation/devicetree/bindings/pwm/nvidia,tegra20-pwm.txt b/Documentation/devicetree/bindings/pwm/nvidia,tegra20-pwm.txt
> > > index c52f03b..2851b2d 100644
> > > --- a/Documentation/devicetree/bindings/pwm/nvidia,tegra20-pwm.txt
> > > +++ b/Documentation/devicetree/bindings/pwm/nvidia,tegra20-pwm.txt
> > > @@ -1,10 +1,12 @@
> > >   Tegra SoC PWFM controller
> > >
> > >   Required properties:
> > > -- compatible: For Tegra20, must contain "nvidia,tegra20-pwm".  For Tegra30,
> > > -  must contain "nvidia,tegra30-pwm".  Otherwise, must contain
> > > -  "nvidia,<chip>-pwm", plus one of the above, where <chip> is tegra114,
> > > -  tegra124, tegra132, or tegra210.
> > > +- compatible: For Tegra20, must contain "nvidia,tegra20-pwm".
> > > +	      For Tegra30, must contain "nvidia,tegra30-pwm".
> > > +	      For Tegra114, Tegra124, Tegra132, Tegra210 must contain
> > > +	      "nvidia,<chip>-pwm", plus one of the above, where <chip> is
> > > +	      tegra114, tegra124, tegra132, or tegra210.
> > > +	      For Tegra186, must contain "nvidia,tegra186-pwm".
> >
> > Rob, I recall discussing this with you a couple of weeks ago, but fail
> > to remember the outcome and can't find a link to the discussion either.
> > Wasn't there a new standard way of documenting this kind of compatible
> > string list?
>
> We did? This is fine for me. However, "plus one of the above" is not
> clear. That means either is valid? If all are "the same" I would expect
> that only nvidia,tegra20-pwm is the fallback. I'm guessing this is
> docuemnting what happened in practice though. Probably should update the
> doc and dts files to reflect desired practice rather than what may be in
> the wild.

FWIW, I've started listing the legal values as explicit separate bullet 
items rather than prose. See the example below - all those entries are 
just one string simply due to the HW design it represents, but each 
entry could be a list (i.e. is a complete compatible value):

- compatible
    Array of strings.
    One of:
    - "nvidia,tegra186-gpio".
    - "nvidia,tegra186-gpio-aon".

could be expanded as e.g.

    - "nvidia,tegra999-gpio", "nvidia,tegra186-gpio"
    ...