linux-kernel - Re: [PATCH 2/2] input: synaptics - fix width calculation on image sensors

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Date:	Mon, 5 Jan 2015 14:07:02 -0500
From:	Benjamin Tissoires <benjamin.tissoires@...il.com>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Gabriele Mazzotta <gabriele.mzt@...il.com>,
	Henrik Rydberg <rydberg@...omail.se>,
	linux-input <linux-input@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Maxwell Anselm <silverhammermba@...il.com>
Subject: Re: [PATCH 2/2] input: synaptics - fix width calculation on image sensors

On Mon, Jan 5, 2015 at 2:04 PM, Dmitry Torokhov
<dmitry.torokhov@...il.com> wrote:
> On January 5, 2015 10:42:13 AM PST, Benjamin Tissoires <benjamin.tissoires@...il.com> wrote:
>>On Mon, Jan 5, 2015 at 1:37 PM, Gabriele Mazzotta
>><gabriele.mzt@...il.com> wrote:
>>> On Monday 05 January 2015 13:25:38 Benjamin Tissoires wrote:
>>>> Hi Gabriele,
>>>>
>>>> On Sat, Dec 27, 2014 at 6:31 AM, Gabriele Mazzotta
>>>> <gabriele.mzt@...il.com> wrote:
>>>> > When two or more fingers are on the touchpad, the 'w' slot holds
>>the
>>>> > finger count rather than the width. Retrieve the correct value
>>encoded
>>>> > in the lower bits of 'x', 'y' and 'z'.
>>>> >
>>>> > The minimum width reported is 8 rather than 4 in this case, while
>>the
>>>> > maximum remains 15.
>>>> >
>>>> > Signed-off-by: Gabriele Mazzotta <gabriele.mzt@...il.com>
>>>> > ---
>>>> >  drivers/input/mouse/synaptics.c | 4 +++-
>>>> >  1 file changed, 3 insertions(+), 1 deletion(-)
>>>> >
>>>> > diff --git a/drivers/input/mouse/synaptics.c
>>b/drivers/input/mouse/synaptics.c
>>>> > index ea0563e..5ff4c5b 100644
>>>> > --- a/drivers/input/mouse/synaptics.c
>>>> > +++ b/drivers/input/mouse/synaptics.c
>>>> > @@ -593,7 +593,9 @@ static void synaptics_parse_agm(const unsigned
>>char buf[],
>>>> >         switch (agm_packet_type) {
>>>> >         case 1:
>>>> >                 /* Gesture packet: (x, y, z) half resolution */
>>>> > -               agm->w = hw->w;
>>>> > +               agm->w = ((buf[1] & 0x01) |
>>>> > +                         ((buf[2] & 0x01) << 1) |
>>>> > +                         ((buf[5] & 0x01) << 2)) + 8;
>>>> >                 agm->x = (((buf[4] & 0x0f) << 8) | buf[1]) << 1;
>>>>
>>>> For completeness, I think, we should also removes the w bits from x,
>>y
>>>> and z (by masking buf[1], buf[2] and buf[5] with 0xfe).
>>>
>>> You are right, I forgot about it.
>>>
>>> I was going to re-submit these patches anyway since there have been
>>> quite a few changes and these can no longer be applied on next.
>>
>>OK, I am trying to put together my thoughts for 1/2 right now. If you
>>could just wait a little before resubmitting, I would be grateful.
>>
>
> BTW, do we really get different widths four different contacts?
>

I think we should. However, on capacitive sensors, the "width" and the
"pressure" fields are 2 ways of sending the same initial information.
Given that we already have two different pressure info, we should thus
get 2 different widths.

Cheers,
Benjamin
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