linux-kernel - Re: [RFC PATCH 1/4] dt-bindings: net: can: add STM32 bxcan DT bindings

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Date:   Mon, 22 Aug 2022 20:39:47 +0300
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Dario Binacchi <dario.binacchi@...rulasolutions.com>
Cc:     linux-kernel@...r.kernel.org,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Amarula patchwork <linux-amarula@...rulasolutions.com>,
        michael@...rulasolutions.com,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        Dario Binacchi <dariobin@...ero.it>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Rob Herring <robh+dt@...nel.org>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        devicetree@...r.kernel.org, linux-can@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [RFC PATCH 1/4] dt-bindings: net: can: add STM32 bxcan DT
 bindings

On 20/08/2022 11:08, Dario Binacchi wrote:
> Hi Krzysztof,
> 
> On Thu, Aug 18, 2022 at 10:22 AM Krzysztof Kozlowski
> <krzysztof.kozlowski@...aro.org> wrote:
>>
>> On 17/08/2022 17:35, Dario Binacchi wrote:
>>> Add documentation of device tree bindings for the STM32 basic extended
>>> CAN (bxcan) controller.
>>>
>>> Signed-off-by: Dario Binacchi <dariobin@...ero.it>
>>> Signed-off-by: Dario Binacchi <dario.binacchi@...rulasolutions.com>
>>
>> You do not need two SoBs. Keep only one, matching the From field.
> 
> I started implementing this driver in my spare time, so my intention
> was to keep track of it.

SoB is not related to copyrights. Keep personal copyrights (with/next to
work ones), but SoB is coming from a person and that's only one. Choose
one "person".

> 
>>
>>> ---
>>>
>>>  .../devicetree/bindings/net/can/st,bxcan.yaml | 139 ++++++++++++++++++
>>>  1 file changed, 139 insertions(+)
>>>  create mode 100644 Documentation/devicetree/bindings/net/can/st,bxcan.yaml
>>>
>>> diff --git a/Documentation/devicetree/bindings/net/can/st,bxcan.yaml b/Documentation/devicetree/bindings/net/can/st,bxcan.yaml
>>> new file mode 100644
>>> index 000000000000..f4cfd26e4785
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/net/can/st,bxcan.yaml
>>
>> File name like compatible, so st,stm32-bxcan-core.yaml (or some other
>> name, see comment later)
> 
>>
>>> @@ -0,0 +1,139 @@
>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>> +%YAML 1.2
>>> +---
>>> +$id: http://devicetree.org/schemas/net/can/st,bxcan.yaml#
>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>> +
>>> +title: STMicroelectronics bxCAN controller Device Tree Bindings
>>
>> s/Device Tree Bindings//
> 
>>
>>> +
>>> +description: STMicroelectronics BxCAN controller for CAN bus
>>> +
>>> +maintainers:
>>> +  - Dario Binacchi <dario.binacchi@...rulasolutions.com>
>>> +
>>> +allOf:
>>> +  - $ref: can-controller.yaml#
>>> +
>>> +properties:
>>> +  compatible:
>>> +    enum:
>>> +      - st,stm32-bxcan-core
>>
>> compatibles are supposed to be specific. If this is some type of
>> micro-SoC, then it should have its name/number. If it is dedicated
>> device, is the final name bxcan core? Google says  the first is true, so
>> you miss specific device part.
> 
> I don't know if I understand correctly, I hope the change in version 2
> is what you requested.

What is the name of the SoC, where this is in?

> 
>>
>>> +
>>> +  reg:
>>> +    maxItems: 1
>>> +
>>> +  resets:
>>> +    maxItems: 1
>>> +
>>> +  clocks:
>>> +    description:
>>> +      Input clock for registers access
>>> +    maxItems: 1
>>> +
>>> +  '#address-cells':
>>> +    const: 1
>>> +
>>> +  '#size-cells':
>>> +    const: 0
>>> +
>>> +required:
>>> +  - compatible
>>> +  - reg
>>> +  - resets
>>> +  - clocks
>>> +  - '#address-cells'
>>> +  - '#size-cells'
>>> +
>>> +additionalProperties: false
>>> +
>>> +patternProperties:
>>
>> This goes after "properties: in top level (before "required").
>>
>>> +  "^can@[0-9]+$":
>>> +    type: object
>>> +    description:
>>> +      A CAN block node contains two subnodes, representing each one a CAN
>>> +      instance available on the machine.
>>> +
>>> +    properties:
>>> +      compatible:
>>> +        enum:
>>> +          - st,stm32-bxcan
>>
>> Why exactly do you need compatible for the child? Is it an entierly
>> separate device?
> 
> I took inspiration from other drivers for ST microcontroller
> peripherals (e. g. drivers/iio/adc/stm32-adc-core.c,
> drivers/iio/adc/stm32-adc.c) where
> some resources are shared between the peripheral instances. In the
> case of CAN, master (CAN1) and slave (CAN2) share the registers for
> configuring the filters and the clock.
> In the core module you can find the functions about the shared
> resources, while the childrens implement the driver.

In both cases you refer to the driver, but we talk here about bindings
which are rather not related. So I repeat the question - is the child
entirely separate device which can be used in other devices?


Best regards,
Krzysztof