linux-kernel - Re: [PATCH 3/4] dt-bindings: serial: document esp32s3-acm bindings

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Message-ID: <CAMo8Bf+u3hkk8zW6EQUtQcAC5t-hUJ5+HoE8JDskBj4KyFK7xA@mail.gmail.com>
Date:   Thu, 14 Sep 2023 13:47:13 -0700
From:   Max Filippov <jcmvbkbc@...il.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
        devicetree@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>
Subject: Re: [PATCH 3/4] dt-bindings: serial: document esp32s3-acm bindings

On Wed, Sep 13, 2023 at 10:57 PM Krzysztof Kozlowski
<krzysztof.kozlowski@...aro.org> wrote:
>
> On 13/09/2023 23:14, Max Filippov wrote:
> > Add documentation for the ESP32S3 ACM controller.
>
> A nit, subject: drop second/last, redundant "bindings". The
> "dt-bindings" prefix is already stating that these are bindings.

Ok.

> > Signed-off-by: Max Filippov <jcmvbkbc@...il.com>
> > ---
> >  .../bindings/serial/esp,esp32-acm.yaml        | 40 +++++++++++++++++++
> >  1 file changed, 40 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/serial/esp,esp32-acm.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/serial/esp,esp32-acm.yaml b/Documentation/devicetree/bindings/serial/esp,esp32-acm.yaml
> > new file mode 100644
> > index 000000000000..dafbae38aa64
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/serial/esp,esp32-acm.yaml
> > @@ -0,0 +1,40 @@
> > +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> > +
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/serial/esp,esp32-acm.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: ESP32S3 ACM controller
> > +
> > +maintainers:
> > +  - Max Filippov <jcmvbkbc@...il.com>
> > +
> > +description: |
>
> Do not need '|' unless you need to preserve formatting.

Ok.

> > +  ESP32S3 ACM controller is a communication device found in the ESP32S3
>
> What is "ACM"?

It's an 'Abstract Control Model' as in USB CDC-ACM: 'Communication Device Class
- Abstract Control Model'.

> Why is this in serial? Only serial controllers are in serial.

Because it's a serial communication device. The SoC TRM calls this peripheral
'USB Serial', but the USB part is fixed and is not controllable on the SoC side.
When you plug it into a host USB socket you get a serial port called ttyACM on
the host.

> The description is very vague, way too vague.

Is the following better?

  Fixed function USB CDC-ACM device controller of the Espressif ESP32S3 SoC.

> > +  SoC that is connected to one of its USB controllers.
>
> Same comments as previous patch.
>
> > +
> > +properties:
> > +  compatible:
> > +    const: esp,esp32s3-acm
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  interrupts:
> > +    maxItems: 1
> > +
> > +required:
> > +  - compatible
> > +  - reg
> > +  - interrupts
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > +  - |
> > +    acm@...38000 {
> > +            compatible = "esp,esp32s3-acm";
>
> Use 4 spaces for example indentation.

Ok.

> > +            reg = <0x60038000 0x1000>;
> > +            interrupts = <96 3 0>;
>
> Same comments as previous patch.

These are not IRQ flags. In any case the contents of the IRQ
specification cells is not relevant here, right?

-- 
Thanks.
-- Max