[PATCH v6 0/4] Input: support overlay objects on touchscreens

[Javier Carrasco <javier.carrasco@wolfvision.net>]

Some touchscreens are shipped with a physical layer on top of them where
a number of buttons and a resized touchscreen surface might be available.

In order to generate proper key events by overlay buttons and adjust the
touch events to a clipped surface, this series offers a documented,
device-tree-based solution by means of helper functions.
An implementation for a specific touchscreen driver is also included.

The functions in touch-overlay provide a simple workflow to acquire
physical objects from the device tree, map them into a list and generate
events according to the object descriptions.

This feature has been tested with a JT240MHQS-E3 display, which consists
of an st1624 as the base touchscreen and an overlay with two buttons and
a frame that clips its effective surface mounted on it.

Signed-off-by: Javier Carrasco <javier.carrasco@wolfvision.net>
---
Changes in v6:
- General: use a single list to manage a single type of object.
- General: swap patches to have bindings preceding the code.
- touch-overlay.c: minor code-sytle fixes.
- Link to v5: https://lore.kernel.org/r/20230510-feature-ts_virtobj_patch-v5-0-ff6b5c4db693@wolfvision.net

Changes in v5:
- touchscreen bindings: move overlay common properties to a $def entry (Rob Herring)
- st1232 bindings: move overlays to the existing example instead of
  making a new one (Rob Herring) 
- Link to v4: https://lore.kernel.org/r/20230510-feature-ts_virtobj_patch-v4-0-5c6c0fc1eed6@wolfvision.net

Changes in v4:
- General: rename "touchscreen" to "touch" to include other consumers.
- PATCH 1/4: move touch-overlay feature to input core.
- PATCH 1/4, 3/4: set key caps and report key events without consumer's
  intervention.
- PATCH 2/4: add missing 'required' field with the required properties.
- Link to v3: https://lore.kernel.org/r/20230510-feature-ts_virtobj_patch-v3-0-b4fb7fc4bab7@wolfvision.net

Changes in v3:
- General: rename "virtobj" and "virtual" to "overlay"
- PATCH 1/4: Make feature bool instead of tristate (selected by
  supported touchscreens)
- Link to v2: https://lore.kernel.org/r/20230510-feature-ts_virtobj_patch-v2-0-f68a6bfe7a0f@wolfvision.net

Changes in v2:
- PATCH 1/4: remove preprocessor directives (the module is selected by
  the drivers that support the feature). Typo in the commit message.
- PATCH 2/4: more detailed documentation. Images and examples were added.
- PATCH 3/4: select ts-virtobj automatically.
- Link to v1: https://lore.kernel.org/r/20230510-feature-ts_virtobj_patch-v1-0-5ae5e81bc264@wolfvision.net

---
Javier Carrasco (4):
      dt-bindings: touchscreen: add touch-overlay property
      Input: touch-overlay - Add touchscreen overlay handling
      dt-bindings: input: touchscreen: st1232: add touch-overlay example
      Input: st1232 - add touch overlays handling

 .../input/touchscreen/sitronix,st1232.yaml         |  29 +++
 .../bindings/input/touchscreen/touchscreen.yaml    | 119 +++++++++
 MAINTAINERS                                        |   7 +
 drivers/input/Makefile                             |   2 +-
 drivers/input/touch-overlay.c                      | 283 +++++++++++++++++++++
 drivers/input/touchscreen/st1232.c                 |  71 +++++-
 include/linux/input/touch-overlay.h                |  24 ++
 7 files changed, 520 insertions(+), 15 deletions(-)
---
base-commit: b85ea95d086471afb4ad062012a4d73cd328fa86
change-id: 20230510-feature-ts_virtobj_patch-e267540aae74

Best regards,
-- 
Javier Carrasco <javier.carrasco@wolfvision.net>