[PATCH v7 1/4] dt-bindings: touchscreen: add touch-overlay property

Javier Carrasco
2024-01-19T07:43:45Z

The touch-overlay encompasses a number of touch areas that define a
clipped touchscreen area and/or buttons with a specific functionality.

A clipped touchscreen area avoids getting events from regions that are
physically hidden by overlay frames.

For touchscreens with printed overlay buttons, sub-nodes with a suitable
key code can be defined to report key events instead of the original
touch events.

Reviewed-by: Jeff LaBundy <jeff@labundy.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Javier Carrasco <javier.carrasco@wolfvision.net>
---
.../bindings/input/touchscreen/touchscreen.yaml | 119 +++++++++++++++++++++
1 file changed, 119 insertions(+)

diff --git a/Documentation/devicetree/bindings/input/touchscreen/touchscreen.yaml b/Documentation/devicetree/bindings/input/touchscreen/touchscreen.yaml
index 431c13335c40..eb1e86fa86c6 100644
--- a/Documentation/devicetree/bindings/input/touchscreen/touchscreen.yaml
+++ b/Documentation/devicetree/bindings/input/touchscreen/touchscreen.yaml
@@ -87,6 +87,125 @@ properties:
touchscreen-y-plate-ohms:
description: Resistance of the Y-plate in Ohms

+ touch-overlay:
+ description: list of nodes defining segments (touch areas) on the
+ touchscreen.
+
+ This object can be used to describe a series of segments to
+ restrict the region within touch events are reported or buttons
+ with a specific functionality.
+
+ This is of special interest if the touchscreen is shipped with a physical
+ overlay on top of it with a frame that hides some part of the original
+ touchscreen area. Printed buttons on that overlay are also a typical
+ use case.
+
+ A new touchscreen area is defined as a sub-node without a key code. If a
+ key code is defined in the sub-node, it will be interpreted as a button.
+
+ The x-origin and y-origin properties of a touchscreen area define the
+ offset of a new origin from where the touchscreen events are referenced.
+ This offset is applied to the events accordingly. The x-size and y-size
+ properties define the size of the touchscreen effective area.
+
+ The following example shows a new touchscreen area with the new origin
+ (0',0') for the touch events generated by the device.
+
+ Touchscreen (full area)
+ ┌────────────────────────────────────────┐
+ │ ┌───────────────────────────────┐ │
+ │ │ │ │
+ │ ├ y-size │ │
+ │ │ │ │
+ │ │ touchscreen area │ │
+ │ │ (no key code) │ │
+ │ │ │ │
+ │ │ x-size │ │
+ │ ┌└──────────────┴────────────────┘ │
+ │(0',0') │
+ ┌└────────────────────────────────────────┘
+ (0,0)
+
+ where (0',0') = (0+x-origin,0+y-origin)
+
+ Sub-nodes with key codes report the touch events on their surface as key
+ events instead.
+
+ The following example shows a touchscreen with a single button on it.
+
+ Touchscreen (full area)
+ ┌───────────────────────────────────┐
+ │ │
+ │ │
+ │ ┌─────────┐ │
+ │ │button 0 │ │
+ │ │KEY_POWER│ │
+ │ └─────────┘ │
+ │ │
+ │ │
+ ┌└───────────────────────────────────┘
+ (0,0)
+
+ Segments defining buttons and clipped toushcreen areas can be combined
+ as shown in the following example.
+ In that case only the events within the touchscreen area are reported
+ as touch events. Events within the button areas report their associated
+ key code. Any events outside the defined areas are ignored.
+
+ Touchscreen (full area)
+ ┌─────────┬──────────────────────────────┐
+ │ │ │
+ │ │ ┌───────────────────────┐ │
+ │ button 0│ │ │ │
+ │KEY_POWER│ │ │ │
+ │ │ │ │ │
+ ├─────────┤ │ touchscreen area │ │
+ │ │ │ (no key code) │ │
+ │ │ │ │ │
+ │ button 1│ │ │ │
+ │ KEY_INFO│ ┌└───────────────────────┘ │
+ │ │(0',0') │
+ ┌└─────────┴──────────────────────────────┘
+ (0,0)
+
+ type: object
+
+ patternProperties:
+ '^segment-':
+ type: object
+ description:
+ Each segment is represented as a sub-node.
+ properties:
+ x-origin:
+ description: horizontal origin of the node area
+ $ref: /schemas/types.yaml#/definitions/uint32
+
+ y-origin:
+ description: vertical origin of the node area
+ $ref: /schemas/types.yaml#/definitions/uint32
+
+ x-size:
+ description: horizontal resolution of the node area
+ $ref: /schemas/types.yaml#/definitions/uint32
+
+ y-size:
+ description: vertical resolution of the node area
+ $ref: /schemas/types.yaml#/definitions/uint32
+
+ label:
+ description: descriptive name of the segment
+ $ref: /schemas/types.yaml#/definitions/string
+
+ linux,code: true
+
+ required:
+ - x-origin
+ - y-origin
+ - x-size
+ - y-size
+
+ unevaluatedProperties: false
+
dependencies:
touchscreen-size-x: [ touchscreen-size-y ]
touchscreen-size-y: [ touchscreen-size-x ]

--
2.39.2