Add device tree binding for UART 1-wire bus.

Signed-off-by: Christoph Winklhofer <cj.winklhofer@gmail.com>
---
 .../devicetree/bindings/w1/w1-uart.yaml       | 44 +++++++++++++++++++
 1 file changed, 44 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/w1/w1-uart.yaml

diff --git a/Documentation/devicetree/bindings/w1/w1-uart.yaml b/Documentation/devicetree/bindings/w1/w1-uart.yaml
new file mode 100644
index 000000000000..93d83c42c407
--- /dev/null
+++ b/Documentation/devicetree/bindings/w1/w1-uart.yaml
@@ -0,0 +1,44 @@
+# 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@gmail.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
+
+required:
+  - compatible
+
+additionalProperties: false
+
+examples:
+  - |
+    serial {
+      onewire {
+        compatible = "w1-uart";
+      };
+    };
-- 
2.43.0

On Thu, Dec 21, 2023 at 07:50:47AM +0100, Christoph Winklhofer wrote:
> Add device tree binding for UART 1-wire bus.
> 
> Signed-off-by: Christoph Winklhofer <cj.winklhofer@gmail.com>
> ---
>  .../devicetree/bindings/w1/w1-uart.yaml       | 44 +++++++++++++++++++
>  1 file changed, 44 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/w1/w1-uart.yaml
> 
> diff --git a/Documentation/devicetree/bindings/w1/w1-uart.yaml b/Documentation/devicetree/bindings/w1/w1-uart.yaml
> new file mode 100644
> index 000000000000..93d83c42c407
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/w1/w1-uart.yaml
> @@ -0,0 +1,44 @@
> +# 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@gmail.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
> +
> +required:
> +  - compatible
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    serial {
> +      onewire {

Have you tried this in an actual DT? Assuming the UART node has a 
schema, it should be a warning because child node names are explicit in 
serial.yaml unfortunately. IOW, you need to add "onewire" to 
serial.yaml.


> +        compatible = "w1-uart";
> +      };
> +    };
> -- 
> 2.43.0
>

On Thu, Dec 21, 2023 at 02:59:58PM -0600, Rob Herring wrote:
> On Thu, Dec 21, 2023 at 07:50:47AM +0100, Christoph Winklhofer wrote:
> > Add device tree binding for UART 1-wire bus.
> > 
> > Signed-off-by: Christoph Winklhofer <cj.winklhofer@gmail.com>
> > ---
> >  .../devicetree/bindings/w1/w1-uart.yaml       | 44 +++++++++++++++++++
> >  1 file changed, 44 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/w1/w1-uart.yaml
> > 
> > diff --git a/Documentation/devicetree/bindings/w1/w1-uart.yaml b/Documentation/devicetree/bindings/w1/w1-uart.yaml
> > new file mode 100644
> > index 000000000000..93d83c42c407
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/w1/w1-uart.yaml
> > @@ -0,0 +1,44 @@
> > +# 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@gmail.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
> > +
> > +required:
> > +  - compatible
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > +  - |
> > +    serial {
> > +      onewire {
> 
> Have you tried this in an actual DT? Assuming the UART node has a 
> schema, it should be a warning because child node names are explicit in 
> serial.yaml unfortunately. IOW, you need to add "onewire" to 
> serial.yaml.
>

Thank you! It was tested on an older DT with the wildcard pattern. I
updated my test-system and now get the warning. On the Raspberry PI, 
a DT overlay was used, in this case there is no warning with:

  make CHECK_DTBS=y overlays/w1-uart.dtbo ARCH=arm

Is it possible to do a validation for a DT overlay? Since the overlay
may be incomplete, only existing nodes or properties could be checked.

Thanks!
Christoph