Re: [PATCH 1/2] dt-bindings: hwmon: add tmp464.yaml

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On 2/9/22 05:36, Agathe Porte wrote:
Add basic description of the tmp464 driver DT bindings.

Signed-off-by: Agathe Porte <agathe.porte@xxxxxxxxx>
---
  .../devicetree/bindings/hwmon/ti,tmp464.yaml  | 106 ++++++++++++++++++
  1 file changed, 106 insertions(+)
  create mode 100644 Documentation/devicetree/bindings/hwmon/ti,tmp464.yaml

diff --git a/Documentation/devicetree/bindings/hwmon/ti,tmp464.yaml b/Documentation/devicetree/bindings/hwmon/ti,tmp464.yaml
new file mode 100644
index 000000000000..aaee652c0067
--- /dev/null
+++ b/Documentation/devicetree/bindings/hwmon/ti,tmp464.yaml
@@ -0,0 +1,106 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/hwmon/ti,tmp464.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: TMP464 temperature sensor
+
+maintainers:
+  - Guenter Roeck <linux@xxxxxxxxxxxx>
+
+description: |
+  ±0.0625°C Remote and Local temperature sensor
+  https://www.ti.com/lit/ds/symlink/tmp464.pdf
+
+properties:
+  compatible:
+    enum:
+      - ti,tmp464
+  reg:
+    maxItems: 1
+
+  '#address-cells':
+    const: 1
+
+  '#size-cells':
+    const: 0
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+patternProperties:
+  "^channel@([0-3])$":
+    type: object
+    description: |
+      Represents channels of the device and their specific configuration.
+
+    properties:
+      reg:
+        description: |
+          The channel number. 0 is local channel, 1-3 are remote channels
+        items:
+          minimum: 0
+          maximum: 3

The chip has 1 local and 4 remote channels.

+
+      label:
+        description: |
+          A descriptive name for this channel, like "ambient" or "psu".
+
+      ti,n-factor:
+        description: |
+          The value (two's complement) to be programmed in the channel specific N correction register.
+          For remote channels only.
+        $ref: /schemas/types.yaml#/definitions/uint32
+        items:
+          minimum: 0
+          maximum: 255
+

This does not seem to match the implementation, which calls
of_property_read_s32() and accepts values from -128 .. 127.
It seems unlikely that 255 is interpreted as -1.

Hmm, is that a bug in the tmp421 driver ? I wonder if anyone
checked that, and if there is an official means to express
negative numbers in devicetree. I see other drivers use
of_property_read_s32(), but I did not find a clear explanation
how to describe negative numbers in devicetree files.

Also, I think other chip configuration properties need to be
described here as well for completeness.

- temperature offsets
- hysteresis
- temperature limits
- conversion rate

+    required:
+      - reg
+
+    additionalProperties: false
+
+examples:
+  - |
+    i2c {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      sensor@4b {
+        compatible = "ti,tmp464";
+        reg = <0x4b>;
+      };
+    };
+  - |
+    i2c {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      sensor@4b {
+        compatible = "ti,tmp464";
+        reg = <0x4b>;
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        channel@0 {
+          reg = <0x0>;
+          ti,n-factor = <0x1>;
+          label = "local";
+        };
+
+        channel@1 {
+          reg = <0x1>;
+          ti,n-factor = <0x0>;
+          label = "somelabel";
+        };
+
+        channel@2 {
+          reg = <0x2>;
+          status = "disabled";
+        };
+      };
+    };




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