Re: [PATCH v3 1/2] dt-bindings: i2c-mux: Add property for settle time
From: Peter Rosin <hidden>
Date: 2021-11-01 14:32:50
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linux-i2c, lkml
On 2021-11-01 13:25, Horatiu Vultur wrote:
quoted hunk ↗ jump to hunk
Some HW requires some time for the signals to settle after the muxing is changed. Allow this time to be specified in device tree. Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com> --- Documentation/devicetree/bindings/i2c/i2c-mux.yaml | 6 ++++++ 1 file changed, 6 insertions(+)diff --git a/Documentation/devicetree/bindings/i2c/i2c-mux.yaml b/Documentation/devicetree/bindings/i2c/i2c-mux.yaml index 24cac36037f5..4628ff6340c1 100644 --- a/Documentation/devicetree/bindings/i2c/i2c-mux.yaml +++ b/Documentation/devicetree/bindings/i2c/i2c-mux.yaml@@ -29,6 +29,12 @@ properties: '#size-cells': const: 0 + settle-time-us: + default: 0 + description: + The time required for the signals to settle. Currently only the + i2c-mux-gpmux driver supports this optional binding.
The information about how i2c-mux-gpmux is special is bound to go stale, and I don't think we should mention such specific details in the binding. What I meant was a generic warnings about optional bindings perhaps not being supported by all drivers, along the lines of this from i2c.txt: "These properties may not be supported by all drivers. However, if a driver wants to support one of the below features, it should adapt these bindings." However, I now notice that this sentence makes no sense. It looks like it should be s/adapt/adopt/. And, in the i2c-mux.yaml case it can simply say "Optional properties" instead of "These properites" (which refers to a subset of properties immediately below the text) since with a yaml binding it is always clear which properties are optional and which are required. Lastly, I guess this warning belongs in the description.
+
patternProperties:
'^i2c@[0-9a-f]+$':
$ref: /schemas/i2c/i2c-controller.yamlSince this is the first optional property, you now need to specify what properties are required, which is everything but settle-time-us. If you don't, all properties are required. Which is not what we want... Something like this should do it, I think: required: - compatible - '#address-cells' - '#size-cells' Cheers, Peter