linux-kernel - Re: [PATCH v3 2/5] input: synaptics - change default width value of cr48 sensors

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Date:	Mon, 23 Mar 2015 22:17:02 +0100
From:	Gabriele Mazzotta <gabriele.mzt@...il.com>
To:	Benjamin Tissoires <benjamin.tissoires@...il.com>
Cc:	linux-input <linux-input@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Henrik Rydberg <rydberg@...math.org>,
	Maxwell Anselm <silverhammermba@...il.com>,
	Peter Hutterer <peter.hutterer@...-t.net>,
	Hans de Goede <hdegoede@...hat.com>, grafi@...fi.jp,
	Oliver Neukum <oneukum@...e.de>
Subject: Re: [PATCH v3 2/5] input: synaptics - change default width value of cr48 sensors

On Monday 23 March 2015 16:48:15 Benjamin Tissoires wrote:
> On Sun, Mar 22, 2015 at 10:43 AM, Gabriele Mazzotta
> <gabriele.mzt@...il.com> wrote:
> > The minimum value these sensors can report is 4, so this should be the
> > value used when W is not reporting the width.
> >
> > Signed-off-by: Gabriele Mazzotta <gabriele.mzt@...il.com>
> > ---
> >  drivers/input/mouse/synaptics.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/input/mouse/synaptics.c b/drivers/input/mouse/synaptics.c
> > index 133e488..a7a0e73 100644
> > --- a/drivers/input/mouse/synaptics.c
> > +++ b/drivers/input/mouse/synaptics.c
> > @@ -1018,7 +1018,7 @@ static void synaptics_process_packet(struct psmouse *psmouse)
> >
> >         if (hw.z > 0 && hw.x > 1) {
> >                 num_fingers = 1;
> > -               finger_width = 5;
> > +               finger_width = 4;
> 
> I am not sure about this change. It looks benign, but I don't get how
> changing the local variable finger_width can change anything in the
> CR48 processing.

I fail to remember why I did this exactly. I think the reason why I did this
was that before e9e8520f229b ("Input: synaptics - use in-kernel tracking for
reporting mt data") cr48 sensors used ABS_TOOL_WIDTH for all the fingers. If
you had two fingers on the touchpad it was possible for the kernel to emit
fake width variations in case you lifted one (5->4) and brought it back
on the touchpad (4->5). I'm actually not sure of this as I have an Image
Sensor, but even if it's correct, it should no longer be a problem since
multiple slots are used and so 5 would only be used for the second slot.

> Except for this one (which could be dropped IMO), the *rest* of the series is:
> Reviewed-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>
> 
> Thanks for pushing this Gabriele.
> 
> Cheers,
> Benjamin
> 
> >                 if (SYN_CAP_EXTENDED(priv->capabilities)) {
> >                         switch (hw.w) {
> >                         case 0 ... 1:
> > --
> > 2.1.4
> >

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