Re: [PATCH 03/12] Input: synaptics - fix minimum reported ABS_TOOL_WIDTH

Chris Bagwell
2011-06-29T19:46:58Z

On Wed, Jun 29, 2011 at 11:48 AM, Daniel Kurtz <djkurtz@chromium.org> wrote:
> Hi Chris,
>
> Thanks for taking a look!
>
> On Wed, Jun 29, 2011 at 9:28 PM, Chris Bagwell <chris@cnpbagwell.com> wrote:
>> On Wed, Jun 29, 2011 at 12:07 AM,  <djkurtz@chromium.org> wrote:
>>> From: Daniel Kurtz <djkurtz@chromium.org>
>>>
>>> Synaptics touchpads report a 'w' value in each data report.
>>> For touchpads that support palm detection, when there is a single finger
>>> on the pad, the 'w' value reports its width in the range 4 to 15.
>>> Thus, the minimum valid width is 4.
>>
>> FYI: I had debated on this as well.  When driver was first modified to
>> report min/max width, the min width of zero was chosen because when
>> not touching the pad a value of zero is forced by driver to user.  So
>> the range is 0, 4-15.
>
> Yup, good catch.  I now see that this is true for the legacy single-touch case.
> For consistency with the existing implementation, I'm ok to drop this patch.
>
> I think we can still keep the range 4-15 for the ABS_MT_TOUCH_MAJOR
> axis, though, right?
> A pure-mt userspace app can get the correct width range, and deduce 0
> fingers from the fact that all MT-B slots have tracking_id == -1.

Yeah, at least I'd consider it an app bug.

For that matter, it should be true of ABS_TOOL_WIDTH as well (we could
change to always send minimum 4 as apart of this patch).

Since we are on it, maybe a year ago I tested a version of this patch
and notice xf86-input-synaptics defaulted to non-useful value for
EmulateTwoFingerMinW because of the scale change. The
xf86-input-synaptics logic in question has since be modified/reverted
so I think thats not an issue anymore.

I found no issues with apps see'ing ABS_TOOL_WIDTH >= 4 always.

Chris
>
> -Dan
>
>>>
>>> Note: Other values of 'w' are used to report special conditions:
>>>  w=0: 2 fingers are on the pad
>>>  w=1: 3 or more fingers are on the pad
>>>  w=2: the packet contains "Advanced Gesture Mode" data.
>>>
>>> Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>
>>> ---
>>>  drivers/input/mouse/synaptics.c |    2 +-
>>>  1 files changed, 1 insertions(+), 1 deletions(-)
>>>
>>> diff --git a/drivers/input/mouse/synaptics.c b/drivers/input/mouse/synaptics.c
>>> index f6d0c04..a4b7801 100644
>>> --- a/drivers/input/mouse/synaptics.c
>>> +++ b/drivers/input/mouse/synaptics.c
>>> @@ -706,7 +706,7 @@ static void set_input_params(struct input_dev *dev, struct synaptics_data *priv)
>>>        }
>>>
>>>        if (SYN_CAP_PALMDETECT(priv->capabilities))
>>> -               input_set_abs_params(dev, ABS_TOOL_WIDTH, 0, 15, 0, 0);
>>> +               input_set_abs_params(dev, ABS_TOOL_WIDTH, 4, 15, 0, 0);
>>>
>>>        __set_bit(EV_KEY, dev->evbit);
>>>        __set_bit(BTN_TOUCH, dev->keybit);
>>> --
>>> 1.7.3.1
>>>
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>