Re: [PATCH v2 09/10] Input: elan_i2c - correct the width/size base value

[Benjamin Tissoires <benjamin.tissoires@redhat.com>]

On Fri, May 24, 2019 at 11:00 AM 廖崇榮 <kt.liao@emc.com.tw> wrote:
>
> Hi
>
> -----Original Message-----
> From: Benjamin Tissoires [mailto:benjamin.tissoires@redhat.com]
> Sent: Friday, May 24, 2019 3:06 PM
> To: 廖崇榮
> Cc: Dmitry Torokhov; Rob Herring; Aaron Ma; Hans de Goede; open list:HID CORE LAYER; lkml; devicetree@vger.kernel.org
> Subject: Re: [PATCH v2 09/10] Input: elan_i2c - correct the width/size base value
>
> On Fri, May 24, 2019 at 5:13 AM 廖崇榮 <kt.liao@emc.com.tw> wrote:
> >
> > Hi Benjamin,
> >
> > Thanks so much for all you do for Elan touchpad.
> >
> > For the width_*, I have a question for it.
> > Our antenna sensors fully occupied the whole touchpad PCB.
> >
> > The Gap between 2 sensors are 7.5 mil (0.19mm).
> > That's why we did not minus one trace.
>
> So, with the P52 I have:
> [  +0.000009] max:    (3045,1731) drivers/input/mouse/elan_i2c_core.c:428
> [  +0.000003] traces: (24,14) drivers/input/mouse/elan_i2c_core.c:429
> [  +0.000002] size:   (98,55) drivers/input/mouse/elan_i2c_core.c:430
> [  +0.000001] res:    (31,31) drivers/input/mouse/elan_i2c_core.c:431
>
> calculated size (max/res): 98 x 56 mm
> true size, as measured: 101 x 60 mm
>
> I list layout information of P52 touchpad as below.
> Physical size : 99 x 58 mm
> Active Area size : ~ 97 * 56 mm, (boarding is 1.008mm for each side)
>
> Sensor layout:
> X Pitch : 4.0286 mm
> Y Pitch : 4.0147 mm
>
> Which gives (without the minus 1):
> width_x = max_x / x_traces = 3045 / 24 = 126.875 -> 3.9885 mm width_y = max_y / y_traces = 1731 / 14 = 123.643 -> 4.0927 mm
>
> -> this gives a total size of the touchpad of: 96 x 57 mm (width_x *
> 24, width_y * 14)
>
> With the minus 1:
> width_x = max_x / x_traces = 3045 / 23 = 132.391 -> 4.2707 mm width_y = max_y / y_traces = 1731 / 14 = 133.154 -> 4.2953 mm
>
> -> this gives a total size of the touchpad of: 102 x 60 mm (width_x *
> 24, width_y * 14)
> and considering traces-1: 98 x 56 mm
>
> Removing 1 to the number of traces gave a squarer values in rows and columns, and this is what is done in the PS/2 driver.
> Also, going back to the size of the touchpad gives a better value when removing 1 on the *traces.
> So maybe when forwarding the properties we should remove one there in the PS/2 driver?
>
> Removing 1 trace may be better for some of previous touchpad. (depending on sensor pattern)
> mk_* indicate the number of trace which is touched, and it's not a precise value.
> I think the usability won't change too much whether removing one trace.
> PS/2 have supported plenty of touchpad. It's better to remain the same.
>

OK, so I guess I should just drop this patch from the series then.

Cheers,
Benjamin