linux-kernel - Re: [RESEND PATCH v4 1/4] dt-bindings: soundwire: add slave bindings

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Date:   Tue, 27 Aug 2019 15:20:22 -0500
From:   Rob Herring <robh@...nel.org>
To:     Vinod Koul <vkoul@...nel.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc:     broonie@...nel.org, spapothi@...eaurora.org,
        bgoswami@...eaurora.org, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org, lgirdwood@...il.com,
        devicetree@...r.kernel.org
Subject: Re: [RESEND PATCH v4 1/4] dt-bindings: soundwire: add slave bindings

On Fri, Aug 23, 2019 at 12:23:40PM +0530, Vinod Koul wrote:
> On 23-08-19, 00:37, Srinivas Kandagatla wrote:
> > This patch adds bindings for Soundwire Slave devices that includes how
> > SoundWire enumeration address and Link ID are used to represented in
> > SoundWire slave device tree nodes.
> > 
> > Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
> > ---
> >  .../soundwire/soundwire-controller.yaml       | 75 +++++++++++++++++++
> >  1 file changed, 75 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/soundwire/soundwire-controller.yaml
> > 
> > diff --git a/Documentation/devicetree/bindings/soundwire/soundwire-controller.yaml b/Documentation/devicetree/bindings/soundwire/soundwire-controller.yaml
> > new file mode 100644
> > index 000000000000..91aa6c6d6266
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/soundwire/soundwire-controller.yaml
> > @@ -0,0 +1,75 @@
> > +# SPDX-License-Identifier: GPL-2.0
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/soundwire/soundwire-controller.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: SoundWire Controller Generic Binding
> 
> Controller does not make sense here, why not use spec terminology and
> say "SoundWire Slave Generic Binding"

It's both IMO. It's describing the structure of child devices of a 
controller (aka a bus).

> 
> > +
> > +maintainers:
> > +  - Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
> > +
> > +description: |
> > +  SoundWire busses can be described with a node for the SoundWire controller
> > +  device and a set of child nodes for each SoundWire slave on the bus.
> > +
> > +properties:
> > +  $nodename:
> > +    pattern: "^soundwire(@.*|-[0-9a-f])*$"

'-[0-9a-f]' was to handle cases like spi-gpio or i2c-gpio. Would a 
bit banged interface be possible here?

> > +
> > +  "#address-cells":
> > +    const: 2
> > +
> > +  "#size-cells":
> > +    const: 0
> > +
> > +patternProperties:
> > +  "^.*@[0-9a-f]+$":

If there are distinct fields in the address, they are typically comma 
separated in the unit-address.

> > +    type: object
> > +
> > +    properties:
> > +      compatible:
> > +      pattern: "^sdw[0-9][0-9a-f]{4}[0-9a-f]{4}[0-9a-f]{2}$"
> > +      description:
> > +	  Is the textual representation of SoundWire Enumeration
> > +	  address. compatible string should contain SoundWire Version ID,
> > +	  Manufacturer ID, Part ID and Class ID in order and shall be in
> > +	  lower-case hexadecimal with leading zeroes.
> > +	  Valid sizes of these fields are
> > +	  Version ID is 1 nibble, number '0x1' represents SoundWire 1.0
> > +	  and '0x2' represents SoundWire 1.1 and so on.
> > +	  MFD is 4 nibbles
> > +	  PID is 4 nibbles
> > +	  CID is 2 nibbles
> > +	  More Information on detail of encoding of these fields can be
> > +	  found in MIPI Alliance DisCo & SoundWire 1.0 Specifications.
> > +
> > +      reg:
> > +        maxItems: 1
> > +        description:
> > +          Instance ID and Link ID of SoundWire Device Address.
> 
> This looks better :) Thanks.
> 
> Apart from the minor nit above this looks good to me, I can merge the
> sdw parts if Rob is fine with them.
> 
> Thanks
> 
> > +
> > +    required:
> > +      - compatible
> > +      - reg
> > +
> > +examples:
> > +  - |
> > +    soundwire@...0000 {
> > +        #address-cells = <2>;
> > +        #size-cells = <0>;
> > +        compatible = "qcom,soundwire-v1.5.0";

This will probably change once I review it. :)

> > +        reg = <0x0c2d0000 0x2000>;
> > +
> > +        speaker@1 {
> > +            compatible = "sdw10217201000";
> > +            reg = <1 0>;
> > +        };
> > +
> > +        speaker@2 {
> > +            compatible = "sdw10217201000";
> > +            reg = <2 0>;
> > +        };
> > +    };
> > +
> > +...
> > -- 
> > 2.21.0
> 
> -- 
> ~Vinod