linux-kernel - Re: [PATCH] pinctrl: sunxi: Use minimal debouncing period as default

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Message-ID: <20241129-amazing-whale-of-proficiency-ee6fd2@houat>
Date: Fri, 29 Nov 2024 16:37:41 +0100
From: Maxime Ripard <mripard@...nel.org>
To: Paul Kocialkowski <paulk@...-base.io>
Cc: linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev, 
	linux-kernel@...r.kernel.org, Uwe Kleine-König <ukleinek@...nel.org>, 
	Chen-Yu Tsai <wens@...e.org>, Jernej Skrabec <jernej.skrabec@...il.com>, 
	Samuel Holland <samuel@...lland.org>, Linus Walleij <linus.walleij@...aro.org>, 
	Paul Kocialkowski <contact@...lk.fr>
Subject: Re: [PATCH] pinctrl: sunxi: Use minimal debouncing period as default

On Wed, Nov 20, 2024 at 11:05:42AM +0100, Paul Kocialkowski wrote:
> Le Wed 20 Nov 24, 09:01, Maxime Ripard a écrit :
> > > > If anything, the status quo doesn't impose anything, it just rolls with
> > > > the hardware default. Yours would impose one though.
> > > 
> > > The result is that it puts a strong limitation and breaks many use cases by
> > > default. I don't think we have to accept whatever register default was chosen
> > > by hardware engineers as the most sensible default choice and pretend that this
> > > is not a policy decision.
> > 
> > You're making it much worse than it is. It doesn't "break many use
> > cases" it broke one, by default, with a supported way to unbreak it, in
> > 12 years.
> 
> I think this is exaggerated. Like I mentioned previously there are *many*
> situations that are not covered by the default.

Note that this statement would be true for any default. The current, the
one you suggest, or any other really. The fact that we have a way to
override it is an acknowledgement that it's not a one size fits all
situation.

> The fact that I'm the first person to bring it up in 12 years doesn't
> change that.

Sure. It does however hint that it seems like it's a sane enough
default.

> Sofar the downside you brought up boils down to: badly-designed
> hardware may have relied on this mechanism to avoid interrupt storms
> that could prevent the system from booting.

It's not about good or bad design. Buttons bounce, HPD signals bounce,
it's just the world we live in.

But let me rephrase if my main objection wasn't clear enough: you want
to introduce an ABI breaking change. With the possibility of breaking
devices that have worked fine so far. That's not ok.

Maxime

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