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

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Message-ID: <20210128133922.khkb4zyccoxdnlyp@pengutronix.de>
Date:   Thu, 28 Jan 2021 14:39:22 +0100
From:   Oleksij Rempel <o.rempel@...gutronix.de>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     "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>,
        Rob Herring <robh+dt@...nel.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 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"
2. Extend the list of "not vendor" prefixes in the prefixes list:
   Documentation/devicetree/bindings/vendor-prefixes.yaml

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?

> 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

Regards,
Oleksij
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