[PATCH 2/5] input: wacom - remove pressure for touch devices

[PATCH 2/5] input: wacom - remove pressure for touch devices

[Ping Cheng]

Touch devices do not report valid pressure or capacitance.

Signed-off-by: Ping Cheng <pingc@wacom.com>
---
 drivers/input/tablet/wacom_sys.c |   14 --------------
 drivers/input/tablet/wacom_wac.c |    6 +++---
 2 files changed, 3 insertions(+), 17 deletions(-)

diff --git a/drivers/input/tablet/wacom_sys.c b/drivers/input/tablet/wacom_sys.c
index 449c0a4..36001eb 100644
--- a/drivers/input/tablet/wacom_sys.c
+++ b/drivers/input/tablet/wacom_sys.c
@@ -228,13 +228,6 @@ static int wacom_parse_hid(struct usb_interface *intf, struct hid_descriptor *hi
 							get_unaligned_le16(&report[i + 3]);
 						i += 4;
 					}
-				} else if (usage == WCM_DIGITIZER) {
-					/* max pressure isn't reported
-					features->pressure_max = (unsigned short)
-							(report[i+4] << 8  | report[i + 3]);
-					*/
-					features->pressure_max = 255;
-					i += 4;
 				}
 				break;
 
@@ -290,13 +283,6 @@ static int wacom_parse_hid(struct usb_interface *intf, struct hid_descriptor *hi
 				pen = 1;
 				i++;
 				break;
-
-			case HID_USAGE_UNDEFINED:
-				if (usage == WCM_DESKTOP && finger) /* capacity */
-					features->pressure_max =
-						get_unaligned_le16(&report[i + 3]);
-				i += 4;
-				break;
 			}
 			break;
 
diff --git a/drivers/input/tablet/wacom_wac.c b/drivers/input/tablet/wacom_wac.c
index c1c2f7b..3eccf21 100644
--- a/drivers/input/tablet/wacom_wac.c
+++ b/drivers/input/tablet/wacom_wac.c
@@ -818,7 +818,6 @@ static int wacom_bpt_touch(struct wacom_wac *wacom)
 				x <<= 5;
 				y <<= 5;
 			}
-			input_report_abs(input, ABS_MT_PRESSURE, p);
 			input_report_abs(input, ABS_MT_POSITION_X, x);
 			input_report_abs(input, ABS_MT_POSITION_Y, y);
 		}
@@ -1056,10 +1055,11 @@ void wacom_setup_input_capabilities(struct input_dev *input_dev,
 			     features->x_fuzz, 0);
 	input_set_abs_params(input_dev, ABS_Y, 0, features->y_max,
 			     features->y_fuzz, 0);
-	input_set_abs_params(input_dev, ABS_PRESSURE, 0, features->pressure_max,
-			     features->pressure_fuzz, 0);
 
 	if (features->device_type == BTN_TOOL_PEN) {
+		input_set_abs_params(input_dev, ABS_PRESSURE, 0, features->pressure_max,
+			     features->pressure_fuzz, 0);
+
 		/* penabled devices have fixed resolution for each model */
 		input_abs_set_res(input_dev, ABS_X, features->x_resolution);
 		input_abs_set_res(input_dev, ABS_Y, features->y_resolution);
-- 
1.7.6

Re: [PATCH 2/5] input: wacom - remove pressure for touch devices

[Chris Bagwell]

On Fri, Aug 12, 2011 at 7:08 PM, Ping Cheng <pinglinux@gmail.com> wrote:
> Touch devices do not report valid pressure or capacitance.
>
> Signed-off-by: Ping Cheng <pingc@wacom.com>
> ---

I'd prefer if we kept pressure support.  At least for Bamboo's with
product ID between 0xd0 and 0xd4.

In my testing of an 0xd1 device, pressure works fine (low pressure and
high pressure work great.  Not much middle pressure sensitivity.
Multi-touch will increase pressure reading.  All pretty common
behaviour).

I don't use the pressure in day-to-day usage but do use it to drive
testing of pressure features of some apps/drivers and so don't want to
lose it.

>From looking at the touch data on Bamboo's > 0xd4 that people have
emailed me, it looks like pressure data was removed from firmware so a
version of this patch will be useful for those.  But that patch needs
to also change the way it parses the touch data to reduce from 8-bits
to 1-bit.

Chris

Re: [PATCH 2/5] input: wacom - remove pressure for touch devices

[Dmitry Torokhov]

On Mon, Aug 15, 2011 at 09:34:23PM -0700, Ping Cheng wrote:
> On Sun, Aug 14, 2011 at 8:27 PM, Chris Bagwell <chris@cnpbagwell.com> wrote:
> 
> > On Fri, Aug 12, 2011 at 7:08 PM, Ping Cheng <pinglinux@gmail.com> wrote:
> > > Touch devices do not report valid pressure or capacitance.
> > >
> > > Signed-off-by: Ping Cheng <pingc@wacom.com>
> > > ---
> >
> > I'd prefer if we kept pressure support.  At least for Bamboo's with
> > product ID between 0xd0 and 0xd4.
> >
> > In my testing of an 0xd1 device, pressure works fine (low pressure and
> > high pressure work great.  Not much middle pressure sensitivity.
> > Multi-touch will increase pressure reading.  All pretty common
> > behaviour).
> >
> 
> Basically, there were three reasons to remove the pressure bit for all touch
> devices:
> 
> 1.   The value is not a pressure and it does not report valid capacitance
> either;
> 2.   The only valid use in the kernel driver is to decide if the finger is
> touching the tablet or not, which has already been correctly reported by the
> firmware in the other bits. So, it is redundant to check the pressure for
> this purpose;
> 3.   Passing the invalid "pressure" to the user land would only introduce
> bad user experience since touch is not designed for drawing. We don't want
> to confuse user with that "pressure".

Not speaking about touch per se, but pressure is important for other
things besides drawing. Different people prefer different device
sensitivity and if userspace knows pressure it can adjust according to
user preference, like synaptics X driver does with touchpads that
actually report it. I believe tslib allows similar for touchscreens.

Thanks.

-- 
Dmitry

Re: [PATCH 2/5] input: wacom - remove pressure for touch devices

[Dmitry Torokhov]

On Wed, Aug 17, 2011 at 08:32:28AM -0700, Ping Cheng wrote:
> On Tue, Aug 16, 2011 at 11:50 PM, Dmitry Torokhov <dmitry.torokhov@gmail.com
> > wrote:
> 
> > On Mon, Aug 15, 2011 at 09:34:23PM -0700, Ping Cheng wrote:
> > > On Sun, Aug 14, 2011 at 8:27 PM, Chris Bagwell <chris@cnpbagwell.com>
> > wrote:
> > >
> > > > On Fri, Aug 12, 2011 at 7:08 PM, Ping Cheng <pinglinux@gmail.com>
> > wrote:
> > > > > Touch devices do not report valid pressure or capacitance.
> > > > >
> > > > > Signed-off-by: Ping Cheng <pingc@wacom.com>
> > > > > ---
> > > >
> > > > I'd prefer if we kept pressure support.  At least for Bamboo's with
> > > > product ID between 0xd0 and 0xd4.
> > > >
> > > > In my testing of an 0xd1 device, pressure works fine (low pressure and
> > > > high pressure work great.  Not much middle pressure sensitivity.
> > > > Multi-touch will increase pressure reading.  All pretty common
> > > > behaviour).
> > > >
> > >
> > > Basically, there were three reasons to remove the pressure bit for all
> > touch
> > > devices:
> > >
> > > 1.   The value is not a pressure and it does not report valid capacitance
> > > either;
> > > 2.   The only valid use in the kernel driver is to decide if the finger
> > is
> > > touching the tablet or not, which has already been correctly reported by
> > the
> > > firmware in the other bits. So, it is redundant to check the pressure for
> > > this purpose;
> > > 3.   Passing the invalid "pressure" to the user land would only introduce
> > > bad user experience since touch is not designed for drawing. We don't
> > want
> > > to confuse user with that "pressure".
> >
> > Not speaking about touch per se, but pressure is important for other
> > things besides drawing. Different people prefer different device
> > sensitivity and if userspace knows pressure it can adjust according to
> > user preference, like synaptics X driver does with touchpads that
> > actually report it. I believe tslib allows similar for touchscreens.
> >
> 
> Your suggestion is based on the assumption that the value is pressure.

I did not make any assumptions, I was just making general observation
that if pressure data is available it is useful not only for drawing
applications.

> But
> that is not true. The value is not pressure and it is unreliable.

So what is this data then?

Thanks.

-- 
Dmitry