linux-kernel - Re: [PATCH v2 5/7] dt-bindings: sound: Add support for the Lantiq PEF2256 codec

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Message-ID: <20230320191700.3d48e264@bootlin.com>
Date:   Mon, 20 Mar 2023 19:17:00 +0100
From:   Herve Codina <herve.codina@...tlin.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Derek Kiernan <derek.kiernan@...inx.com>,
        Dragan Cvetic <dragan.cvetic@...inx.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.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 v2 5/7] dt-bindings: sound: Add support for the Lantiq
 PEF2256 codec

Hi Krzysztof

On Fri, 17 Mar 2023 09:57:11 +0100
Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> wrote:

> On 16/03/2023 13:27, Herve Codina wrote:
> > The Lantiq PEF2256, also known as Infineon PEF2256 or FALC256, 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.
> >   
> 
> Your other file should also have specific compatible, unless this codec
> is actually part of the framer. Did not look like this in the binding -
> not $ref.

No sure to understand what you mean.

Anyway, I plan to use a MFD device for pef2256 and reference this yaml
from the lantiq,pef2256.yaml in the node related to the codec.

One question related to bindings and related checks:
Is there a way to check the compatible property of the parent node.
I mean, here is the binding of a child node of a MFD node.
From this binding, I would like to be sure that the parent is really a
pef2256 MFD node.

May be something like:
  parent-properties:
    allOf:
      compatible:
        contains:
          const: lantiq,pef2256

The idea is to have dtbs_check raise an error if the parent's compatible
property is not 'lantiq,pef2256'.

From parent, the link is checked using:
  properties:
    codec:
      $ref: /schemas/sound/lantiq,pef2256-codec.yaml

but nothing prevent to use this 'lantiq,pef2256-codec' binding from a node
that has nothing to do with pef2256.

> 
> > Signed-off-by: Herve Codina <herve.codina@...tlin.com>
> > ---
> >  .../bindings/sound/lantiq,pef2256-codec.yaml  | 57 +++++++++++++++++++
> >  1 file changed, 57 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..acba3a0ccd1b
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/sound/lantiq,pef2256-codec.yaml
> > @@ -0,0 +1,57 @@
> > +# 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 device  
> 
> Drop "device". Everything is "device".

Will be dropped in v3 series.

> 
> > +
> > +maintainers:
> > +  - Herve Codina <herve.codina@...tlin.com>
> > +
> > +description: |
> > +  Codec support for PEF2256.
> > +
> > +  The Lantiq PEF2256, also known as Infineon PEF2256 or FALC256, 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.
> > +
> > +allOf:
> > +  - $ref: /schemas/spi/spi-peripheral-props.yaml#

Oups,
This device is not on a SPI bus -> will be dropped in v3 series.

> > +  - $ref: dai-common.yaml#
> > +
> > +properties:
> > +  compatible:
> > +    const: lantiq,pef2256-codec
> > +
> > +  lantiq,pef2256:
> > +    $ref: /schemas/types.yaml#/definitions/phandle
> > +    description:
> > +      phandle to the PEF2256  
> 
> Why not its child? Why this is in parallel ?

Indeed,
I will move to MFD, remove this phandle and use the lantiq,pef2256-codec
node as a child node of lantiq,pef2256.

> 
> > +
> > +  '#sound-dai-cells':
> > +    const: 0
> > +  
> 
> 
> Best regards,
> Krzysztof
> 

Thanks for the review,

Best regards,
Hervé

-- 
Hervé Codina, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com