linux-kernel - Re: [PATCH v4 1/3] dt-bindings: w1: UART 1-Wire bus

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Message-ID: <20240113013917.GA3795949-robh@kernel.org>
Date: Fri, 12 Jan 2024 19:39:17 -0600
From: Rob Herring <robh@...nel.org>
To: Christoph Winklhofer <cj.winklhofer@...il.com>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Jonathan Corbet <corbet@....net>, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
	linux-doc@...r.kernel.org
Subject: Re: [PATCH v4 1/3] dt-bindings: w1: UART 1-Wire bus

On Sat, Jan 06, 2024 at 05:02:24PM +0100, Christoph Winklhofer wrote:
> Add device tree binding for UART 1-Wire bus.
> 
> Signed-off-by: Christoph Winklhofer <cj.winklhofer@...il.com>
> ---
>  Documentation/devicetree/bindings/w1/w1-uart.yaml | 62 +++++++++++++++++++++++
>  1 file changed, 62 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/w1/w1-uart.yaml b/Documentation/devicetree/bindings/w1/w1-uart.yaml
> new file mode 100644
> index 000000000000..6b90693b2ca0
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/w1/w1-uart.yaml
> @@ -0,0 +1,62 @@
> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/w1/w1-uart.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: UART 1-Wire Bus
> +
> +maintainers:
> +  - Christoph Winklhofer <cj.winklhofer@...il.com>
> +
> +description: |
> +  UART 1-wire bus. Utilizes the UART interface via the Serial Device Bus
> +  to create the 1-Wire timing patterns.
> +
> +  The UART peripheral must support full-duplex and operate in open-drain
> +  mode. The timing patterns are generated by a specific combination of
> +  baud-rate and transmitted byte, which corresponds to a 1-Wire read bit,
> +  write bit or reset pulse.
> +
> +  The default baud-rate for reset and presence detection is 9600 and for
> +  a 1-Wire read or write operation 115200. In case the actual baud-rate
> +  is different from the requested one, the transmitted byte is adapted
> +  to generate the 1-Wire timing patterns.
> +
> +  https://www.analog.com/en/technical-articles/using-a-uart-to-implement-a-1wire-bus-master.html
> +
> +
> +properties:
> +  compatible:
> +    const: w1-uart
> +
> +  reset-speed:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    default: 9600
> +    description: |

Don't need '|' if no formatting

> +      The baud rate for the 1-Wire reset and presence detect.
> +
> +  touch_0-speed:

Don't use '_' in property names.

I'm somewhat familar with 1-wire, but I don't get what 'touch' means 
here. I assume these are low and high times which are a function of the 
baudrate.


> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    default: 115200
> +    description: |
> +      The baud rate for the 1-Wire write-0 cycle (touch bit 0).
> +
> +  touch_1-speed:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    default: 115200
> +    description: |
> +      The baud rate for the 1-Wire write-1 and read cycle (touch bit 1).
> +
> +required:
> +  - compatible
> +
> +additionalProperties: false

w1.txt says there can be a child node for the 1-wire device. You need 
'type: object'. Or w1.txt needs to be converted to schema and referenced 
here (along with using unevaluatedProperties here instead).

Rob