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

[Dmitry Torokhov]

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@xxxxxxxxx>
> > 
> > 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@xxxxxx>
> > Signed-off-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
> > ---
> >  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.

Thanks.

-- 
Dmitry
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