linux-kernel - Re: [PATCH v4 1/2] dt-bindings: counter: add pulse-counter binding

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Date:   Fri, 5 Feb 2021 17:34:24 -0600
From:   Rob Herring <robh@...nel.org>
To:     Oleksij Rempel <o.rempel@...gutronix.de>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        linux-iio <linux-iio@...r.kernel.org>,
        Robin van der Gracht <robin@...tonic.nl>,
        William Breathitt Gray <vilhelm.gray@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        David Jander <david@...tonic.nl>,
        Jonathan Cameron <jic23@...nel.org>
Subject: Re: [PATCH v4 1/2] dt-bindings: counter: add pulse-counter binding

On Thu, Jan 28, 2021 at 02:39:22PM +0100, Oleksij Rempel wrote:
> On Thu, Jan 28, 2021 at 09:17:23AM +0100, Linus Walleij wrote:
> > Hi Oleksij,
> > 
> > thanks for your patch!
> > 
> > On Tue, Jan 26, 2021 at 2:15 PM Oleksij Rempel <o.rempel@...gutronix.de> wrote:
> > 
> > > Add binding for the pulse counter node
> > >
> > > Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>
> > (...)
> > 
> > > +properties:
> > > +  compatible:
> > > +    const: virtual,pulse-counter
> > 
> > What is so virtual about this? The device seems very real.
> 
> Currently there are two ways:
> 1. use "virtual" or "linux" vendor. Same as "virtual,mdio-gpio"

virtual is used by exactly one case. linux for a few more, mostly 
linux,spdif-dit and extcon (deprecated).

> 2. Extend the list of "not vendor" prefixes in the prefixes list:
>    Documentation/devicetree/bindings/vendor-prefixes.yaml

Pretty sure that says 'DON'T ADD MORE'. Maybe I forgot to scream it.

> 
> Since both ways seems to be valid, i personally prefer to use existing
> prefix instead of maintaining the vendor-prefixes.yaml
> 
> @Rob, what do you prefer?

For vendorless bindings, no vendor prefix! 'gpio-counter' if only gpio 
interfaced. No idea what other options would be.

> 
> > However it is certainly a GPIO counter.
> 
> This was my first implementation. @Jonathan you suggest to use GPIO-free
> way, can you and Linus please decide what is the way to go.
> 
> I personally can imagine that this driver can be attached to any IRQ
> source, including drivers/iio/trigger/iio-trig-sysfs.c
> 
> > I would call it "gpio-counter" simply.
> > 
> > Define:
> >   $nodename:
> >      pattern: "^counter(@.*)?$"
> > 
> > > +    counter-0 {
> > 
> > counter@0 {
> > 
> > > +    counter-1 {
> > 
> > counter@1 {
> 
> In this case the dtc compiler will say:
> /counter@0: node has a unit name, but no reg property

counter-0 then.

> 
> Regards,
> Oleksij
> -- 
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