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

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Date:	Mon, 5 Jan 2015 14:26:24 -0500
From:	Benjamin Tissoires <benjamin.tissoires@...il.com>
To:	Gabriele Mazzotta <gabriele.mzt@...il.com>
Cc:	Dmitry Torokhov <dmitry.torokhov@...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 2:15 PM, Gabriele Mazzotta
<gabriele.mzt@...il.com> wrote:
> On Monday 05 January 2015 11:04:07 Dmitry Torokhov 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?
>>
>> Thanks.
>
> I think that only the width of the last finger that was laid on the
> touchpad is reported.

According to the Synaptics PS2 Interfacing guide, the width of the
primary finger is also reported. See
http://www.synaptics.com/sites/default/files/511-000275-01_RevB.pdf
section 3.2.10. page 32)

Cheers,
Benjamin
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