ts_read does not work for multitouch-only device without EV_KEY

[kliu128]

Hi,

Thanks to b8594cc, my touchscreen (a Melfas MMSxx on a Galaxy Nexus) now works with tslib despite not emitting the singletouch API's EV_KEY event (as detailed in #102). Now, ts_test_mt works, as do programs using the ts_read_mt API. However, ts_test and programs using ts_read (like DirectFB) do not, though from #103 it seems that both ts_read and ts_read_mt should work for multitouch devices.

Perhaps the problem is that the touchscreen only implements the Linux multitouch API, and none of the single-touch one? Here's an evtest snippet from a single touch:

Event: time 115.790557, type 3 (EV_ABS), code 57 (ABS_MT_TRACKING_ID), value 0
Event: time 115.790588, type 3 (EV_ABS), code 48 (ABS_MT_TOUCH_MAJOR), value 13
Event: time 115.790588, type 3 (EV_ABS), code 58 (ABS_MT_PRESSURE), value 183
Event: time 115.790588, type 3 (EV_ABS), code 53 (ABS_MT_POSITION_X), value 345
Event: time 115.790588, type 3 (EV_ABS), code 54 (ABS_MT_POSITION_Y), value 371
Event: time 115.790618, -------------- SYN_REPORT ------------
Event: time 115.808166, type 3 (EV_ABS), code 57 (ABS_MT_TRACKING_ID), value -1
Event: time 115.808166, -------------- SYN_REPORT ------------

Here's the evtest info, copied from #102:

No device specified, trying to scan all of /dev/input/event*
Available devices:
/dev/input/event0:	barometer
/dev/input/event1:	Melfas MMSxxx Touchscreen
/dev/input/event2:	tuna-gpio-keypad
/dev/input/event3:	proximity
/dev/input/event4:	lightsensor-level
/dev/input/event5:	Tuna Headset Jack
Select the device event number [0-5]: 1
Input driver version is 1.0.1
Input device ID: bus 0x18 vendor 0x0 product 0x0 version 0x0
Input device name: "Melfas MMSxxx Touchscreen"
Supported events:
  Event type 0 (EV_SYN)
  Event type 3 (EV_ABS)
    Event code 47 (ABS_MT_SLOT)
      Value      0
      Min        0
      Max        9
    Event code 48 (ABS_MT_TOUCH_MAJOR)
      Value      0
      Min        0
      Max       30
    Event code 53 (ABS_MT_POSITION_X)
      Value      0
      Min        0
      Max      719
    Event code 54 (ABS_MT_POSITION_Y)
      Value      0
      Min        0
      Max     1279
    Event code 57 (ABS_MT_TRACKING_ID)
      Value      0
      Min        0
      Max    65535
    Event code 58 (ABS_MT_PRESSURE)
      Value      0
      Min        0
      Max      255
Properties:
  Property type 1 (INPUT_PROP_DIRECT)

[merge]

Thanks for reporting. I'll have a look during the upcoming days...

[merge]

Has it worked before? Which version of tslib works, which doesn't?

[kliu128]

I don't think ts_read has ever worked in the past -- this touchscreen only started working at all with b8594cc, which was only a few commits ago. Previously there was a check for EV_KEY (which seems to have been around for at least 9 years) that prevented both ts_read and ts_read_mt from working. TSLib didn't even believe the device was a touchscreen.

[craftyguy]

Here is the ts.conf we are using: https://ptpb.pw/mkAO

[merge]

Thanks for the data. Up until now this has been intended behaviour. While ts_read_mt() is the far better choice, also from the filters' point of view, I'll think about whether supporting ts_read() is worth it. In the end we'd have to rethink differentiating between MT and singletouch devices at all.

That said I'm happy to help supporting ts_read_mt() in your application too.

[merge]

It might be worth testing ts_read() (or directfb, whatever) with this device using the current git code here again.

[craftyguy]

Thanks, building a package now for users to test this on MT-only devices

[kliu128]

Thanks for the quick response, @merge!

9f2345a partially fixes the issue (so that ts_test can track movement with my MT-only touchscreen), but it still seems to not register releases (that is, it never outputs an event of pressure=0 when lifting my finger).

Here's a run of ts_test where I repeatedly tapped the screen:

67.145935:    400    835    172
67.221160:    400    835    172
67.799804:    384    857    172
67.865051:    380    863    172
68.347412:    382    884    174
68.422515:    382    901    176
68.906585:    379    906    173
68.961090:    379    912    171
69.250854:    381    886    188
69.269958:    381    869    197
69.289031:    384    858    189
69.298217:    387    847    161
69.307189:    387    848    135
69.577575:    391    850    157
69.605895:    393    852    132
69.614318:    394    853    126

None of the events show pressure=0 in the third column.

[merge]

thanks for the update, I thought so. I pushed another fix on top of it now. Please note that, although I think it should work and closed the issue in this commit, I didn't test, so please re-open it, if it doesn't yet work for you!

thanks for testing!!

[craftyguy]

@merge

Thank you so much! I'll get this out to folks to test ASAP. We REALLY appreciate your hard work and willingness to help :)

[kliu128]

Confirming that it works! Touches are now detected by DirectFB. Thanks so much for your help!

[merge]

my pleasure. thanks for testing so quickly.