Re: Trouble with an HP stylus

["Éric Brunet" <Eric.Brunet@lps.ens.fr>]

Hi!

Thanks for both answers.

To recall the context:

>PRODUCT=3/3eb/840b/111
>NAME="Atmel Atmel maXTouch Digitizer Pen"
>
>Playing with evtest, it appears that the kernel reports the X coordinate
>in ABS_X and in ABS_Y, while the Y coordinate goes into ABS_Z and ABS_RX;
 
> I have already seen this Atmel panel, and the problem was that they used
> twice X then twice Y to report coordinates:
> 
> diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
> index 2619f7f..b70d4c3 100644
> --- a/drivers/hid/hid-input.c
> +++ b/drivers/hid/hid-input.c
> @@ -603,7 +603,7 @@ static void hidinput_configure_usage(struct hid_input
> *hidinput, struct hid_fiel if (field->flags & HID_MAIN_ITEM_RELATIVE)
> map_rel(usage->hid & 0xf);
>                         else
> -                               map_abs(usage->hid & 0xf);
> +                               map_abs_clear(usage->hid & 0xf);
>                         break;
> 
>                 case HID_GD_HATSWITCH: 

Yep, this patch helps. It helps a lot. the ABS_X and ABS_Y coordinates are now 
correct, the ABS_Z and ABS_RX coordinates are gone, I can point and click with 
the pen.

However, things do not work totally as expected, and the pen remains unusable 
for many drawing applications. I am not sure if the problem lies in the 
input/hid system, or in Xorg's evdev driver or in the applications, but the 
problem I am about to describe occurs only with the pen: everything works as 
expected with the touchpad (recognized as a simple mouse) or with the finger on 
the touchscreen:
  * when I try to make annotations with okular with the "draw a freehand line" 
tool, the line I draw with the pen jumps (drawing a straight line) to some 
apparently random point outside okular's window and jumps back (drawing 
another straight line) to where the pen is, several times per second. I don't 
want to send a jpg to the whole mailing list, but I can send a snapshot on a 
private email on request.
  * when I try to use a drawing tool with gimp or mypaint, each time I raise
the pen and put it at some other place to make another drawing, a straight line 
is drawn between the last and the new position of the pen.

Here is what happens on evtest if I touch the screen with the pen, move a
bit and stops touching; I didn't see anything suspicious, except maybe that 
sometimes there is a single ABS_X or a single ABS_Y without the other 
coordinate between two SYN_REPORT.

Event: time 1406710046.690615, type 1 (EV_KEY), code 320 (BTN_TOOL_PEN), value 1
Event: time 1406710046.690615, type 3 (EV_ABS), code 0 (ABS_X), value 3279
Event: time 1406710046.690615, type 3 (EV_ABS), code 1 (ABS_Y), value 2555
Event: time 1406710046.690615, -------------- SYN_REPORT ------------
Event: time 1406710046.697616, type 4 (EV_MSC), code 4 (MSC_SCAN), value d0042
Event: time 1406710046.697616, type 1 (EV_KEY), code 330 (BTN_TOUCH), value 1
Event: time 1406710046.697616, -------------- SYN_REPORT ------------
Event: time 1406710046.713550, type 3 (EV_ABS), code 0 (ABS_X), value 3287
Event: time 1406710046.713550, type 3 (EV_ABS), code 1 (ABS_Y), value 2539
[ Many other EV_ABS events]
Event: time 1406710047.317556, type 3 (EV_ABS), code 0 (ABS_X), value 3755
Event: time 1406710047.317556, type 3 (EV_ABS), code 1 (ABS_Y), value 1699
Event: time 1406710047.317556, -------------- SYN_REPORT ------------
Event: time 1406710047.340556, type 4 (EV_MSC), code 4 (MSC_SCAN), value d0042
Event: time 1406710047.340556, type 1 (EV_KEY), code 330 (BTN_TOUCH), value 0
Event: time 1406710047.340556, -------------- SYN_REPORT ------------
Event: time 1406710047.342504, type 1 (EV_KEY), code 320 (BTN_TOOL_PEN), value 0
Event: time 1406710047.342504, -------------- SYN_REPORT ------------

Thanks again for the patch,

        Éric Brunet
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