Re: [PATCH v8 15/26] pwm: jz4740: Add support for the JZ4725B

[Uwe Kleine-König]

[Adding Linus Walleij to Cc:]

Hello,

On Thu, Dec 13, 2018 at 03:03:15PM +0100, Paul Cercueil wrote:
> Le jeu. 13 déc. 2018 à 10:24, Uwe Kleine-König
> <u.kleine-koenig@xxxxxxxxxxxxxx> a écrit :
> > On Wed, Dec 12, 2018 at 11:09:10PM +0100, Paul Cercueil wrote:
> > >  The PWM in the JZ4725B works the same as in the JZ4740, except that
> > > it
> > >  only has 6 channels available instead of 8.
> > 
> > this driver is probed only from device tree? If yes, it might be
> > sensible to specify the number of PWMs there and get it from there.
> > There doesn't seem to be a generic binding for that, but there are
> > several drivers that could benefit from it. (This is a bigger project
> > though and shouldn't stop your patch. Still more as it already got
> > Thierry's ack.)
> 
> I think there needs to be a proper guideline, as there doesn't seem to be
> a consensus about this. I learned from emails with Rob and Linus (Walleij)
> that I should not have in devicetree what I can deduce from the compatible
> string.

I understood them a bit differently. It is ok to deduce things from the
compatible string. But if you define a generic property (say) "num-pwms"
that is used uniformly in most bindings this is ok, too. (And then the
two different devices could use the same compatible.)

An upside of the generic "num-pwms" property is that the pwm core could
sanity check pwm phandles before passing them to the hardware drivers.

Best regards
Uwe

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Pengutronix e.K.                           | Uwe Kleine-König            |
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