linux-kernel - Re: [PATCH v5 1/4] gpio: mvebu: Add limited PWM support

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Date:   Mon, 24 Apr 2017 11:15:24 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Ralph Sennhauser <ralph.sennhauser@...il.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Mark Rutland <mark.rutland@....com>,
        Jason Cooper <jason@...edaemon.net>,
        Alexandre Courbot <gnurou@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "linux-pwm@...r.kernel.org" <linux-pwm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Gregory Clement <gregory.clement@...e-electrons.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
Subject: Re: [PATCH v5 1/4] gpio: mvebu: Add limited PWM support

On Fri, Apr 21, 2017 at 11:19 AM, Thomas Petazzoni
<thomas.petazzoni@...e-electrons.com> wrote:

> I clearly don't want to block this, but I believe this is a very good
> illustration of why stable DT bindings simply don't work. We are
> realizing here that having each GPIO bank represented as a separate DT
> node doesn't work, because this blinking functionality is not per GPIO
> bank, but global to all GPIO banks.
>
> I am totally fine with compromise, and having things simple first, and
> extend them later if needed. But this stable DT binding rule makes this
> quite impossible: what is a compromise today might put you in big
> troubles tomorrow.

Really "stable bindings" I never believed in. It's just a pipe dream.

Well they might become stable when the system is "finished"
whenever that happens.

I think a better rationale is that of the IETF:
"rough consensus and running code", make deployed DTs work,
if they are not deployed, or only getting deployed together with the
kernel, changing the bindings are not a problem.

Yours,
Linus Walleij