[PATCH v6 02/19] dt-bindings: auxdisplay: ht16k33: Document Adafruit segment displays

[Geert Uytterhoeven]

The Holtek HT16K33 LED controller is not only used for driving
dot-matrix displays, but also for driving segment displays.

Document compatible values for the Adafruit 7-segment[1] and
14-segment[2] FeatherWing expansion boards with red displays.  According
to the schematics, all other Adafruit 7-segment and 14-segment display
backpack and FeatherWing expansion boards (including bare boards and
boards fitted with displays) are compatible with these two boards.

[1] https://www.adafruit.com/product/3108
[2] https://www.adafruit.com/product/3130

Signed-off-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Reviewed-by: Rob Herring <robh@xxxxxxxxxx>
---
v6:
  - No changes,

v5:
  - Add Reviewed-by,

v4:
  - Combine compatible values for 7/14 segment displays into an enum,

v3:
  - Drop color property,

v2:
  - Fix type of color to uint32,
  - "refresh-rate-hz" is still required for dot-matrix displays.

Alternatives I considered:
  1. Document the attached display type in a child node.
     I.e. specify segment type, number of characters, and wiring.
     Especially the latter would become really complex, due to the sheer
     amount of possible wiring combinations.
     Using this method, you also loose the ability to just connect a
     display to an i2c bus, and instantiate the device from sysfs,
     without using DT:

	echo adafruit,3130 0x70 > /sys/class/i2c/i2c-adapter/.../new_device

  2. Document all Adafruit 7-segment and 14-segment display backpack and
     FeatherWing expansion boards.
     This would lead to a myriad of compatible values:

      - items:
	  - enum:
	      - adafruit,878      # 0.56" 4-Digit 7-Segment Display Backpack (Red)
	      - adafruit,879      # 0.56" 4-Digit 7-Segment Display Backpack (Yellow)
	      - adafruit,880      # 0.56" 4-Digit 7-Segment Display Backpack (Green)
	      - adafruit,881      # 0.56" 4-Digit 7-Segment Display Backpack (Blue)
	      - adafruit,1002     # 0.56" 4-Digit 7-Segment Display Backpack (White)
	  - const: adafruit,877   # 0.56" 4-Digit 7-Segment Backpack
	  - const: holtek,ht16k33

      - items:
	  - enum:
	      - adafruit,1268     # 1.2" 4-Digit 7-Segment Display Backpack (Green)
	      - adafruit,1269     # 1.2" 4-Digit 7-Segment Display Backpack (Yellow)
	      - adafruit,1270     # 1.2" 4-Digit 7-Segment Display Backpack (Red)
	  - const: adafruit,1271  # 1.2" 4-Digit 7-Segment Backpack
	  - const: holtek,ht16k33

      - items:
	  - enum:
	      - adafruit,1911     # 0.54" Quad Alphanumeric Display Backpack (Red)
	      - adafruit,1912     # 0.54" Quad Alphanumeric Display Backpack (Blue)
	      - adafruit,2157     # 0.54" Quad Alphanumeric Display Backpack (White)
	      - adafruit,2158     # 0.54" Quad Alphanumeric Display Backpack (Yellow)
	      - adafruit,2159     # 0.54" Quad Alphanumeric Display Backpack (Yellow-Green)
	      - adafruit,2160     # 0.54" Quad Alphanumeric Display Backpack (Green)
	  - const: adafruit,1910  # 0.54" Quad 14-segment Alphanumeric Backpack
	  - const: holtek,ht16k33

      - items:
	  - enum:
	      - adafruit,3106     # 0.56" 4-Digit 7-Segment FeatherWing Display (Blue)
	      - adafruit,3107     # 0.56" 4-Digit 7-Segment FeatherWing Display (Green)
	      - adafruit,3108     # 0.56" 4-Digit 7-Segment FeatherWing Display (Red)
	      - adafruit,3109     # 0.56" 4-Digit 7-Segment FeatherWing Display (White)
	      - adafruit,3110     # 0.56" 4-Digit 7-Segment FeatherWing Display (Yellow)
	  - const: adafruit,3088  # 0.56" 4-Digit 7-Segment FeatherWing
	  - const: holtek,ht16k33

      - items:
	  - enum:
	      - adafruit,3127     # 0.54" Quad Alphanumeric FeatherWing Display (White)
	      - adafruit,3128     # 0.54" Quad Alphanumeric FeatherWing Display (Blue)
	      - adafruit,3129     # 0.54" Quad Alphanumeric FeatherWing Display (Green)
	      - adafruit,3130     # 0.54" Quad Alphanumeric FeatherWing Display (Red)
	      - adafruit,3131     # 0.54" Quad Alphanumeric FeatherWing Display (Yellow)
	      - adafruit,3132     # 0.54" Quad Alphanumeric FeatherWing Display (Yellow-Green)
	  - const: adafruit,3089  # 0.54" Quad 14-segment Alphanumeric FeatherWing
	  - const: holtek,ht16k33
---
 .../bindings/auxdisplay/holtek,ht16k33.yaml   | 20 ++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/Documentation/devicetree/bindings/auxdisplay/holtek,ht16k33.yaml b/Documentation/devicetree/bindings/auxdisplay/holtek,ht16k33.yaml
index 64ffff460026040f..6baf1200c9d8488e 100644
--- a/Documentation/devicetree/bindings/auxdisplay/holtek,ht16k33.yaml
+++ b/Documentation/devicetree/bindings/auxdisplay/holtek,ht16k33.yaml
@@ -14,14 +14,21 @@ allOf:
 
 properties:
   compatible:
-    const: holtek,ht16k33
+    oneOf:
+      - items:
+          - enum:
+              - adafruit,3108  # 0.56" 4-Digit 7-Segment FeatherWing Display (Red)
+              - adafruit,3130  # 0.54" Quad Alphanumeric FeatherWing Display (Red)
+          - const: holtek,ht16k33
+
+      - const: holtek,ht16k33     # Generic 16*8 LED controller with dot-matrix display
 
   reg:
     maxItems: 1
 
   refresh-rate-hz:
     maxItems: 1
-    description: Display update interval in Hertz
+    description: Display update interval in Hertz for dot-matrix displays
 
   interrupts:
     maxItems: 1
@@ -44,7 +51,14 @@ properties:
 required:
   - compatible
   - reg
-  - refresh-rate-hz
+
+if:
+  properties:
+    compatible:
+      const: holtek,ht16k33
+then:
+  required:
+    - refresh-rate-hz
 
 additionalProperties: false
 
-- 
2.25.1