[PATCH 1/3] dt-bindings: backlight: ti,lp8864: Add backlight class properties

From: Alexander Sverdlin <[email protected]>

Extend the TI LP8864/LP8866 device-tree binding to support backlight
class properties alongside the existing LED class child node.

This is a preparatory change for converting the LP8864 driver from a
pure LED class driver to additionally register a backlight class device,
motivated by a use case on a hot-pluggable segment of an I2C bus. The
generic led-backlight driver (led_bl.c) is a platform driver and thus
inherently non-hotpluggable, which makes it unsuitable for hardware
topologies where the backlight controller resides on a hot-pluggable I2C
bus segment. By making the LP8864 driver itself register a backlight
class device, it becomes a native I2C driver that properly supports
hot-plug/unplug events.

The binding is updated to:
- Reference backlight common.yaml at the top level, making
  default-brightness and max-brightness valid optional properties
- Make the "led" child node optional rather than required, since the
  backlight class device is now the primary interface
- Use unevaluatedProperties instead of additionalProperties to properly
  allow properties inherited from the referenced common schema

The LED child node is preserved for backward compatibility with existing
device-trees. No in-tree device-trees reference this binding, so this
change has no impact on existing mainline users.

Signed-off-by: Alexander Sverdlin <[email protected]>
---
 .../bindings/leds/backlight/ti,lp8864.yaml       | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/Documentation/devicetree/bindings/leds/backlight/ti,lp8864.yaml b/Documentation/devicetree/bindings/leds/backlight/ti,lp8864.yaml
index d44232d462bde..11d7e3840c6fb 100644
--- a/Documentation/devicetree/bindings/leds/backlight/ti,lp8864.yaml
+++ b/Documentation/devicetree/bindings/leds/backlight/ti,lp8864.yaml
@@ -4,7 +4,7 @@
 $id: http://devicetree.org/schemas/leds/backlight/ti,lp8864.yaml#
 $schema: http://devicetree.org/meta-schemas/core.yaml#
 
-title: Texas Instruments - LP8864/LP8866 4/6-Channel LED Driver family
+title: Texas Instruments - LP8864/LP8866 4/6-Channel LED Backlight Driver family
 
 maintainers:
   - Andrew Davis <[email protected]>
@@ -21,6 +21,9 @@ description: |
     https://www.ti.com/product/LP8866-Q1
     https://www.ti.com/product/LP8866S-Q1
 
+allOf:
+  - $ref: common.yaml#
+
 properties:
   compatible:
     const: ti,lp8864
@@ -36,9 +39,15 @@ properties:
   vled-supply:
     description: LED supply
 
+  default-brightness:
+    maximum: 65535
+
+  max-brightness:
+    maximum: 65535
+
   led:
     type: object
-    $ref: common.yaml#
+    $ref: /schemas/leds/common.yaml#
     properties:
       function: true
       color: true
@@ -50,9 +59,8 @@ properties:
 required:
   - compatible
   - reg
-  - led
 
-additionalProperties: false
+unevaluatedProperties: false
 
 examples:
   - |
-- 
2.54.0