[PATCH RFC] dt-bindings: display: document display panel occlusions
Caleb Connolly
caleb.connolly at linaro.org
Mon Oct 9 17:32:50 UTC 2023
Some display panels found in modern phones and laptops feature
non-standard display shapes with features like rounded corners, notches
(sections of the display that are cut-out from the edge), and cutouts
(such as circular "hole punch" camera cutouts, or wider pill-shaped
"islands").
Some discussion has been underway previously on how best to describe
these features [1][2], including a reference userspace implementation
using SVG paths [3]. Using this previous discussion as a jumping off
point, this RFC allows for describing the following display features:
* Corner radius (on a per-corner basis)
* Circular or pill-shaped cutouts
* Notches with arbitrary shapes
It's easy to make a case for only using rectangles to describe these
missing parts of a display, however this severely limits their utility.
Describing display occlusions as accurately as possible allows for a lot of
useful UX features. For example, displaying a ring around a hole-punch
camera when it's in use, or wrapping UI elements around a notch. These
behaviours are only possible to implement when the dimensions are known
with near pixel-perfect accuracy.
Cutouts are described as rectangles with a width, height, and corner
radius.
A radius of half the width longest edge will definitionally be an ellipse.
This simple description is suitable for describing hole-punch cameras,
as well
as pill-shaped cutouts. I'm not aware of any devices that can't be
described like this.
Notches are a little more complicated, they usually feature convex and
concave corners as well as straight lines. Here they are described as a
sequence of optionally disjoint arcs, where the space between one arc ending
and another starting is inferred to be a straight line.
Each arc is described with an X and Y pixel coordinate, a radius, and a
start and end point in degrees. These arcs can precisely describe the
shape of a notch, and easily allow for a basic bounding box to be
derived using the min/max coordinates specified in the path.
Some displays feature partially occluded edges ("waterfall edges") where
the screen bends, it may be useful for user interfaces to avoid placing
certain UI elements like buttons too close to these edges. These edges
are described by a distance from the edge where it begins to be
occluded, and the number of degrees that the display curves (this
directly affects how usable this edge of the screen is).
[1]: https://lore.kernel.org/dri-devel/f8747f99-0695-5be0-841f-4f72ba5d5da3@connolly.tech/
[2]: https://gitlab.freedesktop.org/wayland/wayland-protocols/-/issues/87
[3]: https://gitlab.gnome.org/World/Phosh/gmobile
Signed-off-by: Caleb Connolly <caleb.connolly at linaro.org>
---
Some folks have previously suggested that this information belongs in
userspace and not in devicetree. I would like to be clear that
devicetree is for describing hardware, and parts of a display which can
never actually be seen are very much properties of the underlying
hardware.
---
base-commit: 268c4b354d66908697299063c44c0b553b01d935
// Caleb (they/them)
---
.../bindings/display/panel/panel-common.yaml | 7 +
.../bindings/display/panel/panel-occlusions.yaml | 182 +++++++++++++++++++++
2 files changed, 189 insertions(+)
diff --git a/Documentation/devicetree/bindings/display/panel/panel-common.yaml b/Documentation/devicetree/bindings/display/panel/panel-common.yaml
index 0a57a31f4f3d..6ea52a031872 100644
--- a/Documentation/devicetree/bindings/display/panel/panel-common.yaml
+++ b/Documentation/devicetree/bindings/display/panel/panel-common.yaml
@@ -150,6 +150,13 @@ properties:
controller, this property contains a phandle that references the
controller.
+ occlusions:
+ $ref: panel-occlusions.yaml#
+ description:
+ Some panels have non-standard shapes due to features like rounded corners,
+ notches, cutouts, and "waterfall" edges. The panel-occlusions bindings
+ can be used to describe these features.
+
dependencies:
width-mm: [ height-mm ]
height-mm: [ width-mm ]
diff --git a/Documentation/devicetree/bindings/display/panel/panel-occlusions.yaml b/Documentation/devicetree/bindings/display/panel/panel-occlusions.yaml
new file mode 100644
index 000000000000..0932026bbd8c
--- /dev/null
+++ b/Documentation/devicetree/bindings/display/panel/panel-occlusions.yaml
@@ -0,0 +1,182 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/display/panel/panel-occlusions.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Common Properties for describing display notches, cutouts, and other occlusions
+
+maintainers:
+ - Caleb Connolly <caleb.connolly at linaro.org>
+
+description: |
+ This document defines devicetree nodes that can be used to describe
+ different kind of display occlusions such as notches, camera cutouts, rounded
+ corners, and other features that may require special treatment by the display
+ subsystem. All pixel values should be given in the displays native resolution.
+
+properties:
+ $nodename:
+ const: occlusions
+
+ corners:
+ type: object
+ description: |
+ An area of the display which is fully obscured by a notch.
+ properties:
+ radius-px:
+ $ref: /schemas/types.yaml#/definitions/uint32
+ description: Describes the radius when it's identical for all corners
+
+ radius-top-px:
+ $ref: /schemas/types.yaml#/definitions/uint32
+ description: Describes the radius when it's identical for both top corners
+
+ radius-bottom-px:
+ $ref: /schemas/types.yaml#/definitions/uint32
+ description: Describes the radius when it's identical for both top corners
+
+ radius-top-left-px:
+ $ref: /schemas/types.yaml#/definitions/uint32
+ description: The radius of the top left corner in pixels
+
+ radius-top-right-px:
+ $ref: /schemas/types.yaml#/definitions/uint32
+ description: The radius of the top right corner in pixels
+
+ radius-bottom-left-px:
+ $ref: /schemas/types.yaml#/definitions/uint32
+ description: The radius of the bottom left corner in pixels
+
+ radius-bottom-right-px:
+ $ref: /schemas/types.yaml#/definitions/uint32
+ description: The radius of the bottom right corner in pixels
+
+ dependencies:
+ radius-top-left-px: [ radius-top-right-px ]
+ radius-top-right-px: [ radius-top-left-px ]
+ radius-bottom-left-px: [ radius-bottom-right-px ]
+ radius-bottom-right-px: [ radius-bottom-left-px ]
+
+ anyOf:
+ - required:
+ - radius-px
+ - required:
+ - radius-top-px
+ - radius-bottom-px
+ - required:
+ - radius-top-px
+ - radius-bottom-left-px
+ - radius-bottom-right-px
+ - required:
+ - radius-bottom-px
+ - radius-top-left-px
+ - radius-top-right-px
+ - required:
+ - radius-top-left-px
+ - radius-top-right-px
+ - radius-bottom-left-px
+ - radius-bottom-right-px
+
+ additionalProperties: false
+
+patternProperties:
+ "^cutout(-[0-9])?$":
+ type: object
+ description: |
+ An area of the display which is not directly adjacent to an
+ edge and is fully occluded (for example, a camera cutout).
+ properties:
+ x-position-px:
+ $ref: /schemas/types.yaml#/definitions/uint32
+ description: The horizontal coordinate of the center of the cutout.
+
+ y-position-px:
+ $ref: /schemas/types.yaml#/definitions/uint32
+ description: The horizontal coordinate of the center of the cutout.
+
+ width-px:
+ $ref: /schemas/types.yaml#/definitions/uint32
+ description: The width of the cutout in pixels.
+
+ height-px:
+ $ref: /schemas/types.yaml#/definitions/uint32
+ description: The width of the cutout in pixels.
+
+ corner-radius-px:
+ $ref: /schemas/types.yaml#/definitions/uint32
+ description: |
+ The radius of the corners in pixels. For a circle this should be half of
+ the width/height.
+
+ required:
+ - x-position-px
+ - y-position-px
+ - width-px
+ - height-px
+ - corner-radius-px
+
+ additionalProperties: false
+
+ "^notch(-[0-9])?$":
+ type: object
+ description: |
+ An area of the display which is fully occluded by a notch.
+ properties:
+ path:
+ $ref: /schemas/types.yaml#/definitions/uint32-matrix
+ description: |
+ Sequence of values defining the arcs which describe this path. Lines
+ are inserted between arcs that don't directly meet.
+ maxItems: 8 # Ought to cover most scenarios
+ items:
+ items:
+ - description: X coordinate of center point in pixels
+ - description: Y coordinate of center point in pixels
+ - description: Circle radius
+ - description: Starting angle in degrees
+ - description: Ending angle in degrees
+
+ required:
+ - path
+
+ additionalProperties: false
+
+ "^(left|right|top|bottom)-edge$":
+ type: object
+ description: |
+ An edge of the screen with reduced visibility due to a waterfall design
+ or similar.
+ properties:
+ size-px:
+ $ref: /schemas/types.yaml#/definitions/uint32
+ description: The distance from the edge where it begins to obscure visbility
+
+ curve-degrees:
+ $ref: /schemas/types.yaml#/definitions/uint32
+ description: The number of degrees that the display curves.
+ maximum: 100
+
+ required:
+ - size-px
+ - curve-degrees
+
+additionalProperties: false
+
+examples:
+ - | # A panel with a large-ish notch on the top edge, and different corner radii
+ panel {
+ occlusions {
+ notch {
+ path = <360 8 10 0 90>,
+ <435 10 20 270 180>,
+ <645 10 20 180 90>,
+ <645 8 10 90 0>;
+ };
+
+ corners {
+ radius-top-px = <30>;
+ radius-bottom-px = <40>;
+ };
+ };
+ };
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