[PATCH v4 08/13] dt-bindings: iio: adc: adi,ad4134: Document SPI connection mode

[Marcelo Schmitt <marcelo.schmitt@analog.com>]

Document how AD4134 chips are connected to the host SPI controller
according to different wiring configurations.

Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
---
Change log v3 -> v4:
- Properly specified vendor custom property, avoiding 'too few spaces after comma' warn.
- Correctly restrained the value/number of spi-rx-bus-width lanes for
  two-channel-chain use case.
- Improved the constraint to also prevent specifying one-channel-chain or
  two-channel-chain without #daisy-chained-devices.

 .../bindings/iio/adc/adi,ad4134.yaml          | 57 ++++++++++++++++---
 1 file changed, 50 insertions(+), 7 deletions(-)

diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad4134.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad4134.yaml
index ea6d7e026419..970e7adb2405 100644
--- a/Documentation/devicetree/bindings/iio/adc/adi,ad4134.yaml
+++ b/Documentation/devicetree/bindings/iio/adc/adi,ad4134.yaml
@@ -131,6 +131,26 @@ properties:
     enum: [ free-running, gated ]
     default: gated
 
+  adi,spi-mode:
+    $ref: /schemas/types.yaml#/definitions/string
+    enum: [ no-cs, 4-wire, one-channel-chain, two-channel-chain ]
+    default: no-cs
+    description: |
+      This property indicates the SPI wiring configuration.
+      * no-cs: The datasheet calls this "minimum I/O mode". In this mode, the CS
+        line is not used (tied to GND).
+      * 4-wire: Specifies a conventional SPI wiring configuration.
+      * one-channel-chain: In this mode, the DOUT0 line of one chip is connected
+        to DOUT2 of the next chip upstream in the chain. Only the data interface
+        of the upmost device in the stream is in direct connection with the
+        digital host.
+      * two-channel-chain: In this mode, the DOUT0 and DOUT1 lines of one chip
+        are respectively connected to DOUT2 and DOUT3 of the next chip upstream
+        in the chain. Only the data interface of the upmost device in the stream
+        is in direct connection with the digital host.
+
+  '#daisy-chained-devices': true
+
 required:
   - compatible
   - reg
@@ -141,13 +161,36 @@ required:
   - clocks
   - clock-names
 
-oneOf:
-  - required:
-      - ldoin-supply
-  - required:
-      - avdd1v8-supply
-      - dvdd1v8-supply
-      - clkvdd-supply
+allOf:
+  - oneOf:
+      - required:
+          - ldoin-supply
+      - required:
+          - avdd1v8-supply
+          - dvdd1v8-supply
+          - clkvdd-supply
+
+  - oneOf:
+      - required: ['adi,spi-mode', '#daisy-chained-devices']
+        properties:
+          adi,spi-mode:
+            const: one-channel-chain
+          spi-rx-bus-width:
+            const: 1
+      - required: ['adi,spi-mode', '#daisy-chained-devices']
+        properties:
+          adi,spi-mode:
+            const: two-channel-chain
+          spi-rx-bus-width:
+            items:
+              - const: 1
+              - const: 1
+      - properties:
+          '#daisy-chained-devices': false
+          adi,spi-mode:
+            enum:
+              - no-cs
+              - 4-wire
 
 unevaluatedProperties: false
 
-- 
2.53.0