Re: v4.1 to v4.7: regression in tsc2005 driver

From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
To: Michael Welling <mwelling@ieee.org>
Cc: Pavel Machek <pavel@ucw.cz>,
	kernel list <linux-kernel@vger.kernel.org>,
	linux-input@vger.kernel.org, pali.rohar@gmail.com,
	sre@kernel.org, aaro.koskinen@iki.fi,
	ivo.g.dimitrov.75@gmail.com, patrikbachan@gmail.com,
	serge@hallyn.com
Subject: Re: v4.1 to v4.7: regression in tsc2005 driver
Date: Tue, 19 Jul 2016 17:53:07 -0700	[thread overview]
Message-ID: <20160720005307.GH19250@dtor-ws> (raw)
In-Reply-To: <20160720003908.GA32423@deathstar>

On Tue, Jul 19, 2016 at 07:39:08PM -0500, Michael Welling wrote:
> On Tue, Jul 19, 2016 at 04:51:20PM -0700, Dmitry Torokhov wrote:
> > On Sun, Jul 17, 2016 at 05:56:36PM -0500, Michael Welling wrote:
> > > On Sun, Jul 17, 2016 at 10:03:39PM +0200, Pavel Machek wrote:
> > > > On Sun 2016-07-17 13:51:34, Michael Welling wrote:
> > > > > On Sun, Jul 17, 2016 at 08:42:09PM +0200, Pavel Machek wrote:
> > > > > > On Sun 2016-07-17 13:24:45, Michael Welling wrote:
> > > > > > > On Sun, Jul 17, 2016 at 07:52:57PM +0200, Pavel Machek wrote:
> > > > > > > > Hi!
> > > > > > > > 
> > > > > > > > tsc2005 driver changed input device name, from
> > > > > > > > 
> > > > > > > > drivers/input/touchscreen/tsc2005.c:	  input_dev->name = "TSC2005
> > > > > > > > touchscreen";
> > > > > > > > 
> > > > > > > > to "TSC200X touchscreen". Unfortunately, X seems to propagate that
> > > > > > > > name to userspace, where it is needed to be able to do
> > 
> > Technically X _is_ userspace.
> > 
> > > > > > > > 
> > > > > > > > xinput --set-prop --type=int ...
> > > > > > > > 
> > > > > > > > with the right arguments to calibrate touchscreen. (Touchscreen is
> > > > > > > > unusable without calibration).
> > > > > > > > 
> > > > > > > > What to do with that?
> > 
> > Hmm, I do not think we ever committed for the device names to be stable.
> > You are supposed to locate touchscreen device based on its properties
> > and you might need some heuristic if you encounter a system with more
> > than one such touchscreen.
> > 
> > > > > > > 
> > > > > > > The input_dev name could be passed to the common probe function.
> > > > > > > 
> > > > > > > http://lxr.free-electrons.com/source/drivers/input/touchscreen/tsc2005.c#L65
> > > > > > 
> > > > > > That would be preffered, I guess.
> > > > > > 
> > > > > > How many stable releases are affected?
> > > > > 
> > > > > Well this patch is 9 months old now. Lets see.
> > > > > 
> > > > > It was introduced in v4.4-rc1. So v4.4, v4.5 and v4.6.
> > > > 
> > > > Ok, thanks for the information. I believe changing it back to
> > > > "TSC2005" version makes sense (and then fixing it in stable).
> > 
> > Do we know how many users are affected?
> 
> Anyone with an old N900 and the smarts to update the kernel.

Soo... only Pavel? ;)

> 
> > 
> > > 
> > > Lets see if the maintainer has any input before I submit a patch.
> > 
> > I guess we could also pass the input_id structure to tsc200x_probe, fill
> > the proper product ID (2004 or 2005) and derive the name form it.
> >
> 
> Okay do you really think this should be considered a regression?
> 
> Should I go ahead with the patch?

To "fix" it is a small change so we might as well do that, but I
probably leave it off stable for now.

Thanks.

-- 
Dmitry