linux-kernel - Re: [PATCH 0/2] pinctrl: zynqmp: Support muxing individual pins

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Date: Mon, 3 Jun 2024 11:02:08 +0200
From: Linus Walleij <linus.walleij@...aro.org>
To: Sean Anderson <sean.anderson@...ux.dev>
Cc: Michal Simek <michal.simek@....com>, linux-gpio@...r.kernel.org, 
	Krishna Potthuri <sai.krishna.potthuri@....com>, linux-kernel@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, Conor Dooley <conor+dt@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Rob Herring <robh@...nel.org>, devicetree@...r.kernel.org
Subject: Re: [PATCH 0/2] pinctrl: zynqmp: Support muxing individual pins

On Thu, May 30, 2024 at 7:08 PM Sean Anderson <sean.anderson@...ux.dev> wrote:
> On 5/29/24 04:38, Linus Walleij wrote:
> > On Tue, May 28, 2024 at 4:28 PM Sean Anderson <sean.anderson@...ux.dev> wrote:
> >
> >> Well, perhaps you should have reviewed the original driver more
> >> closely.
> >
> > Do you want to push me down and increase my work related
> > stress? Because that is the effect of such statements.
> >
> > It looks like criticism of me as a person, so explain yourself.
> >
> > Writing this kind of things looks to me like some kind of abusive way
> > to express your desire and that is what burns maintainers out, so
> > if that is what you are doing, stop doing that, adjust your behaviour
> > and focus on technical issues.
>
> The technical issue is that the driver does not match the hardware. We
> must maintain the existing set of groups for backwards-compatibility.
> But this should not prevent improvement.
>
> Saying that we cannot have both group styles means that the driver is
> permanently stuck with whatever was picked when it was submitted. Hence,
> if you want to have only one style you had better review new drivers
> very carefully.

Actually I did say you can rewrite it to the other style, it's just work.

If the previous approach was wrong, just redo it as it should be,
and rewrite the DT bindings and the existing device trees. If
backward-compatibility is so important, add a new driver with a new
unique Kconfig CONFIG_PINCTRL_ZYNQMP_V2 and new bindings
on the side and select one from a new compatible such as
"xlnx,zynqmp-pinctrl-v2", problem solved:
new driver new bindings, can be used on a per-board basis,
can be compiled into the same kernel image.

It may be embarrassing to have to tell the device tree maintainers
that the bindings got wrong three years ago and now we need to roll
a v2, but worse things have happened.

I don't like the approach
"this was done so we cannot redo it", we can always redo things,
it is even expected as proven by Fred Brooks timeless statement
in "The Mythical Man-Month": any team *will* always design
a throw-away system whether they intend it or not, there will be
a second version.

This approach will be more clean, I think? Also it will be
possible to phase over more boards and perhaps eventually
drop the old driver and the old bindings.

I'd like to hear from Xilinx/AMD how they want to solve this
going forward.

Yours,
Linus Walleij