linux-kernel - Re: Please revert 3eea8b5d68c801fec788b411582b803463834752 as it breaks touchscreen on n900.

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Message-ID: <20150602082521.GA14955@amd>
Date:	Tue, 2 Jun 2015 10:25:22 +0200
From:	Pavel Machek <pavel@....cz>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	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: Please revert 3eea8b5d68c801fec788b411582b803463834752 as it
 breaks touchscreen on n900.

On Mon 2015-06-01 14:32:13, Dmitry Torokhov wrote:
> On Mon, Jun 01, 2015 at 11:22:26PM +0200, Maxime Ripard wrote:
> > Hi Dmitry,
> > 
> > On Mon, Jun 01, 2015 at 10:47:30AM -0700, Dmitry Torokhov wrote:
> > > On Mon, Jun 01, 2015 at 05:21:11PM +0200, Pavel Machek wrote:
> > > > 
> > > > 
> > > > > > > > The 3eea8b5d68c801fec788b411582b803463834752 is just bad.
> > > > > > > 
> > > > > > > You were very welcome to review this patch at the time and/or suggest
> > > > > > > a fix that pleases everyone.
> > > > > > 
> > > > > > You should be the one that should suggest fixes, as you broke it in
> > > > > > the first place. But clearly you don't understand that.
> > > > > 
> > > > > You actually never asked for a fix, and went head first calling this
> > > > > patch "bad" and asking for nothing but reverting it.
> > > > 
> > > > Date: Fri, 29 May 2015 21:08:16 +0200
> > > > Subject: 4.1 touchscreen regression on n900 -- pinpointed [was Re:
> > > > linux-n900
> > > > ...
> > > > Maxime, can you suggest a fix?
> > > 
> > > How about we do something like below (it needs a small edt-ft5x06 fixup
> > > that I'll send separately). Not tested.
> > > 
> > > Thanks.
> > > 
> > > -- 
> > > Dmitry
> > > 
> > > 
> > > Input: improve parsing OF parameters for touchscreens
> > > 
> > > From: Dmitry Torokhov <dmitry.torokhov@...il.com>
> > > 
> > > When applying touchscreen parameters specified in device tree let's make
> > > sure we keep whatever setup was done by the driver and not reset the
> > > missing values to zero.
> > > 
> > > Reported-by: Pavel Machek <pavel@....cz>
> > > Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
> > > ---
> > >  drivers/input/touchscreen/edt-ft5x06.c     |    2 -
> > >  drivers/input/touchscreen/of_touchscreen.c |   67 ++++++++++++++++++----------
> > >  drivers/input/touchscreen/tsc2005.c        |    2 -
> > >  include/linux/input/touchscreen.h          |    5 +-
> > >  4 files changed, 48 insertions(+), 28 deletions(-)
> > > 
> > > diff --git a/drivers/input/touchscreen/edt-ft5x06.c b/drivers/input/touchscreen/edt-ft5x06.c
> > > index 29d179a..394b1de 100644
> > > --- a/drivers/input/touchscreen/edt-ft5x06.c
> > > +++ b/drivers/input/touchscreen/edt-ft5x06.c
> > > @@ -1041,7 +1041,7 @@ static int edt_ft5x06_ts_probe(struct i2c_client *client,
> > >  			     0, tsdata->num_y * 64 - 1, 0, 0);
> > >  
> > >  	if (!pdata)
> > > -		touchscreen_parse_of_params(input);
> > > +		touchscreen_parse_of_params(input, true);
> > >  
> > >  	error = input_mt_init_slots(input, MAX_SUPPORT_POINTS, INPUT_MT_DIRECT);
> > >  	if (error) {
> > > diff --git a/drivers/input/touchscreen/of_touchscreen.c b/drivers/input/touchscreen/of_touchscreen.c
> > > index b82b520..c132624 100644
> > > --- a/drivers/input/touchscreen/of_touchscreen.c
> > > +++ b/drivers/input/touchscreen/of_touchscreen.c
> > > @@ -14,14 +14,22 @@
> > >  #include <linux/input/mt.h>
> > >  #include <linux/input/touchscreen.h>
> > >  
> > > -static u32 of_get_optional_u32(struct device_node *np,
> > > -			       const char *property)
> > > +static bool touchscreen_get_property_u32(struct device_node *np,
> > > +					 const char *property,
> > > +					 unsigned int default_value,
> > > +					 unsigned int *value)
> > >  {
> > >  	u32 val = 0;
> > > +	int error;
> > >  
> > > -	of_property_read_u32(np, property, &val);
> > > +	error = of_property_read_u32(np, property, &val);
> > > +	if (error) {
> > > +		*value = default_value;
> > > +		return false;
> > > +	}
> > >  
> > > -	return val;
> > > +	*value = val;
> > > +	return true;
> > 
> > This looks good.
> > 
> > However, of_property_read_u32 already does the right thing here by not
> > update val if the property is not found.
> 
> I know but it is not documented anywhere (as far as I know) so I'd
> rather not rely on the implementation detail that might change in the
> future. This is not a hot path so extra assignment should not hurt.

Seriously? Submit a patch documenting it, instead of writing strange
code. I bet everyone and their dog relies on it.
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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