[Bug 1897553] Re: [ALPS i2c Touchpads] Palm detect pressure is too easy to trigger so that the cursor stalled

[Daniel van Vugt]

** Summary changed:

- Palm detect pressure is too easy to trigger so that the cursor stalled
+ [ALPS i2c Touchpads] Palm detect pressure is too easy to trigger so that the cursor stalled

** Tags added: focal groovy

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https://bugs.launchpad.net/bugs/1897553

Title:
  [ALPS i2c Touchpads] Palm detect pressure is too easy to trigger so
  that the cursor stalled

Status in OEM Priority Project:
  New
Status in libinput package in Ubuntu:
  In Progress
Status in libinput source package in Focal:
  New

Bug description:
  [Impact]

   * ALPS new i2c touchpads have capabilities for reporting ABS_PRESSURE and
     ABS_MT_PRESSURE event, However, it is very easy to over the default
     palm detect by pressure threshold 130. When the threshold is achieved,
     the cursor will be stalled, and not be able to keep following the
     finger's movement.

  [Test Case]

   * For touchpad vid 0488, and have pressure capabilities.

     The pressure capability can be easily obtain by evtest tool, there 
     should be ABS_PRESSURE and ABS_MT_PRESSURE event in ABS event type.

     Test step:
     Install libinput-tools
     1. $ sudo apt install libinput-tools
     2. $ sudo libinput measure touchpad-pressure
     3. Generally move the finger, the pressure max should not exceed the
        palm pressure detect threshold

  [Regression Potential]

   * It only impacts ALPS i2c models
   * It won't impact the touchpad without capability to report pressure event.
   * For those touchpad with pressure capability will make the palm detect 
     pressure be less sensitive. However, ALPS said its firmware can support 
     firmware labeling palm detection, so it is okay that the palm detect 
     pressure become less sensitive.

  [Other Info]

   * The upstream commit has merged
     https://gitlab.freedesktop.org/libinput/libinput/-/merge_requests/505

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