linux-kernel - Re: [PATCH v3 4/6] dt-bindings: sound: Add support for the Lantiq PEF2256 codec

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Date:   Thu, 23 Mar 2023 08:31:28 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Herve Codina <herve.codina@...tlin.com>
Cc:     Lee Jones <lee@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, alsa-devel@...a-project.org,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v3 4/6] dt-bindings: sound: Add support for the Lantiq
 PEF2256 codec

On 23/03/2023 08:27, Herve Codina wrote:
> Hi Krzysztof
> 
> On Wed, 22 Mar 2023 22:59:37 +0100
> Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> wrote:
> 
>> On 22/03/2023 14:46, Herve Codina wrote:
>>> The Lantiq PEF2256 is a framer and line interface component designed to
>>> fulfill all required interfacing between an analog E1/T1/J1 line and the
>>> digital PCM system highway/H.100 bus.
>>>
>>> The codec support allows to use some of the PCM system highway
>>> time-slots as audio channels to transport audio data over the E1/T1/J1
>>> lines.
>>>
>>> Signed-off-by: Herve Codina <herve.codina@...tlin.com>
>>> ---
>>>  .../bindings/sound/lantiq,pef2256-codec.yaml  | 54 +++++++++++++++++++
>>>  1 file changed, 54 insertions(+)
>>>  create mode 100644 Documentation/devicetree/bindings/sound/lantiq,pef2256-codec.yaml
>>>
>>> diff --git a/Documentation/devicetree/bindings/sound/lantiq,pef2256-codec.yaml b/Documentation/devicetree/bindings/sound/lantiq,pef2256-codec.yaml
>>> new file mode 100644
>>> index 000000000000..da35b70cda99
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/sound/lantiq,pef2256-codec.yaml
>>> @@ -0,0 +1,54 @@
>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>> +%YAML 1.2
>>> +---
>>> +$id: http://devicetree.org/schemas/sound/lantiq,pef2256-codec.yaml#
>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>> +
>>> +title: Lantiq PEF2256 codec
>>> +
>>> +maintainers:
>>> +  - Herve Codina <herve.codina@...tlin.com>
>>> +
>>> +description: |
>>> +  Codec support for PEF2256.
>>> +
>>> +  The Lantiq PEF2256, also known as Infineon PEF2256 or FALC56, is a framer and
>>> +  line interface component designed to fulfill all required interfacing between
>>> +  an analog E1/T1/J1 line and the digital PCM system highway/H.100 bus.
>>> +
>>> +  The codec support allows to use some of the PCM system highway time-slots as
>>> +  audio channels to transport audio data over the E1/T1/J1 lines.
>>> +
>>> +  The time-slots used by the codec must be set and so, the properties
>>> +  'dai-tdm-slot-num', 'dai-tdm-slot-width', 'dai-tdm-slot-tx-mask' and
>>> +  'dai-tdm-slot-rx-mask' must be present in the ALSA sound card node for
>>> +  sub-nodes that involve the codec. The codec uses 8bit time-slots.
>>> +  'dai-tdm-tdm-slot-with' must be set to 8.
>>> +  The tx and rx masks define the PEF2256 time-slots assigned to the codec.
>>> +
>>> +  The PEF2256 codec node should be a child of a PEF2256 node.
>>> +  Refer to the bindings described in
>>> +  Documentation/devicetree/bindings/mfd/lantiq,pef2256.yaml
>>> +
>>> +allOf:
>>> +  - $ref: dai-common.yaml#
>>> +
>>> +properties:
>>> +  compatible:
>>> +    const: lantiq,pef2256-codec
>>> +
>>> +  '#sound-dai-cells':
>>> +    const: 0  
>>
>> You do not have here any resources, so the entire binding can be dropped
>> and merged into the parent.
>>
>> Best regards,
>> Krzysztof
>>
> 
> Ok,
> Do you expect all these properties (except compatible) merged at the parent

You have only two properties here - dai cells and name-prefix...

> level or may I keep a child node with these properties including the
> compatible property (ie. yaml file merge).

I was thinking that these should be merged into parent because usually
you do not need child node for this. However now I started to think how
the codec driver would look like. Essentially the parent MFD driver
would need to register dais...

Best regards,
Krzysztof