[PATCH v5 04/11] dt-bindings: iio: adc: hx711: add HX710B support

[Piyush Patle <piyushpatle228@gmail.com>]

Add the avia,hx710b compatible and document the HX710B-specific
DVDD and VREF supplies.

Add constraints that forbid HX711-only properties on HX710B nodes and
require vref-supply for HX710B, then add a separate HX710B example.

Keep the existing HX711-only binding extensions in earlier patches so
this change is limited to the new variant.

Signed-off-by: Piyush Patle <piyushpatle228@gmail.com>
---
Changes in v5:
- Split this out of the old combined binding update so the HX710B
  additions stand on their own.
- Require explicit vref-supply for HX710B nodes instead of documenting
  an implicit fallback.
- Use a single if/then/else schema block for the HX710B versus HX711
  property constraints.
Changes in v4:
- Add vref-supply for the HX710B VREF pin.
- Remove dvdd-supply from the HX710B forbidden properties.
- Add an HX710B example and the vref-supply constraint for HX711/HX710B.
- Update the HX710B description to avoid channel-number wording.
Changes in v3:
- Drop the old vref wording from avdd-supply and remove the separate
  HX710B example used earlier.
Changes in v2:
- Add the HX710B-compatible, dvdd-supply, and the initial HX710B/HX711
  constraints in the combined binding update.
---
 .../bindings/iio/adc/avia-hx711.yaml          | 42 ++++++++++++++++++-
 1 file changed, 41 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/iio/adc/avia-hx711.yaml b/Documentation/devicetree/bindings/iio/adc/avia-hx711.yaml
index 9134bbe41379..b2b5c7bdf05e 100644
--- a/Documentation/devicetree/bindings/iio/adc/avia-hx711.yaml
+++ b/Documentation/devicetree/bindings/iio/adc/avia-hx711.yaml
@@ -4,7 +4,7 @@
 $id: http://devicetree.org/schemas/iio/adc/avia-hx711.yaml#
 $schema: http://devicetree.org/meta-schemas/core.yaml#
 
-title: AVIA HX711 ADC chip for weight cells
+title: AVIA HX711 and HX710B ADCs
 
 maintainers:
   - Andreas Klinger <ak@it-klinger.de>
@@ -14,9 +14,14 @@ description: |
   differential input channels. Channel A supports gain 64 and 128;
   channel B supports gain 32.
 
+  The HX710B is a 24-bit ADC with fixed gain of 128. One input measures
+  the differential voltage between the two input pins; a second measures
+  the DVDD-AVDD supply voltage difference for battery level detection.
+
 properties:
   compatible:
     enum:
+      - avia,hx710b
       - avia,hx711
 
   sck-gpios:
@@ -44,6 +49,17 @@ properties:
       RATE pin state is determined by the board wiring.
     maxItems: 1
 
+  dvdd-supply:
+    description:
+      Digital supply voltage (DVDD). For the HX710B, DVDD must be
+      greater than or equal to AVDD. When DVDD is a battery rail and
+      AVDD is a regulated supply, one channel monitors the DVDD-AVDD
+      difference for battery level detection.
+
+  vref-supply:
+    description:
+      Reference voltage input (VREF).
+
   clock-frequency:
     description:
       Controls the SCK bit-bang timing. The value is used to derive the
@@ -53,6 +69,21 @@ properties:
     maximum: 2500000
     default: 400000
 
+allOf:
+  - if:
+      properties:
+        compatible:
+          const: avia,hx710b
+    then:
+      properties:
+        vsup-supply: false
+        rate-gpios: false
+      required:
+        - vref-supply
+    else:
+      properties:
+        vref-supply: false
+
 required:
   - compatible
   - sck-gpios
@@ -72,3 +103,12 @@ examples:
         avdd-supply = <&avdd>;
         clock-frequency = <100000>;
     };
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    weight {
+        compatible = "avia,hx710b";
+        sck-gpios = <&gpio3 10 GPIO_ACTIVE_HIGH>;
+        dout-gpios = <&gpio0 7 GPIO_ACTIVE_HIGH>;
+        avdd-supply = <&avdd>;
+        vref-supply = <&vref>;
+    };
-- 
2.43.0