linux-kernel - [PATCH v4 5/8] dt-bindings: iio: add backend support to sd modulator

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Message-ID: <20240704155338.2387858-6-olivier.moysan@foss.st.com>
Date: Thu, 4 Jul 2024 17:53:33 +0200
From: Olivier Moysan <olivier.moysan@...s.st.com>
To: <fabrice.gasnier@...s.st.com>, Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Arnaud Pouliquen <arnaud.pouliquen@...s.st.com>
CC: Olivier Moysan <olivier.moysan@...s.st.com>, <linux-iio@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH v4 5/8] dt-bindings: iio: add backend support to sd modulator

The legacy sd modulator driver registers the sigma delta modulator as
an IIO channel provider. This implementation is not convenient when the
SD modulator has to be cascaded with another IIO device. The scaling
information is distributed across devices, which makes it difficult to
report consistent scaling data on IIO devices.

The solution is to expose these cascaded IIO devices as an aggregate
device, which report global scaling information.
Add IIO backend support to SD modulator to allow scaling information
management.

Signed-off-by: Olivier Moysan <olivier.moysan@...s.st.com>
---
 .../iio/adc/sigma-delta-modulator.yaml        | 23 +++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/Documentation/devicetree/bindings/iio/adc/sigma-delta-modulator.yaml b/Documentation/devicetree/bindings/iio/adc/sigma-delta-modulator.yaml
index cab0d425eaa4..3f682d95d807 100644
--- a/Documentation/devicetree/bindings/iio/adc/sigma-delta-modulator.yaml
+++ b/Documentation/devicetree/bindings/iio/adc/sigma-delta-modulator.yaml
@@ -18,18 +18,37 @@ properties:
       - sd-modulator
       - ads1201
 
+  '#io-backend-cells':
+    const: 0
+
   '#io-channel-cells':
     const: 0
 
+  reg:
+    maxItems: 1
+
+  vref-supply:
+    description: Phandle to the vref input analog reference voltage.
+
 required:
   - compatible
-  - '#io-channel-cells'
+
+anyOf:
+  - required: ['#io-backend-cells']
+  - required: ['#io-channel-cells']
 
 additionalProperties: false
 
 examples:
   - |
-    ads1202: adc {
+    // Backend binding example. SD modulator configured as an IIO backend device
+    ads1201_0 {
+      compatible = "sd-modulator";
+      #io-backend-cells = <0>;
+    };
+
+    // Legacy binding example. SD modulator configured as an IIO channel provider
+    ads1201_1 {
       compatible = "sd-modulator";
       #io-channel-cells = <0>;
     };
-- 
2.25.1