linux-kernel - Re: [PATCH] fix n900 dts file to work around 4.1 touchscreen regression on n900

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Message-ID: <20150601095556.GH17267@lukather>
Date:	Mon, 1 Jun 2015 11:55:56 +0200
From:	Maxime Ripard <maxime.ripard@...e-electrons.com>
To:	Pavel Machek <pavel@....cz>
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Felipe Balbi <balbi@...com>,
	Sebastian Reichel <sre@...nel.org>,
	kernel list <linux-kernel@...r.kernel.org>,
	pali.rohar@...il.com, sre@...ian.org, sre@...g0.de,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	linux-omap@...r.kernel.org, tony@...mide.com, khilman@...nel.org,
	aaro.koskinen@....fi, ivo.g.dimitrov.75@...il.com,
	patrikbachan@...il.com
Subject: Re: [PATCH] fix n900 dts file to work around 4.1 touchscreen
 regression on n900

On Fri, May 29, 2015 at 10:34:56PM +0200, Pavel Machek wrote:
> Hi!
> 
> > > > single DT, you don't even use that property in your driver, and now
> > > > that you realise you meant something else, you want the code that
> > > 
> > > not Pali, Sebastian.
> > > 
> > > > actually parse the *right* property and does the right thing, that all
> > > > other DT agree (and depend on) to be reverted?
> > > 
> > > We shouldn't revert, that I agree. But both properties should be parsed.
> > 
> > No. If the property is wrong, and nobody parsed it, I do not see any reason to
> > start now.
> 
> Agreed.
> 
> But that's not what I'm asking. See a changelog of
> 3eea8b5d68c801fec788b411582b803463834752 and compare it with what it
> actually does.
> 
> It is buggy. If fuzz is specified but maximum is not, it overwites
> maximum with zero.

If maximum is not set, you'll have other issues anyway. But it really
boils down on what the default behaviour should be.

> Plus it introduces new failure "if (!test_bit(axis, dev->absbit))".

It's not a new failure, it's testing against stupid code.

If an axis is setup in the DT but not registered in the driver,
something is wrong, most probably the DT.

> Plus it fails to distinguish between "value not specified in the dt"
> and "zero is specified in the dt".

Again, default behaviour.

> The 3eea8b5d68c801fec788b411582b803463834752 is just bad.

You were very welcome to review this patch at the time and/or suggest
a fix that pleases everyone.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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