linux-kernel - Re: [RFC PATCH 1/5] dt-bindings: soundwire: add slave bindings

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Message-ID: <20190701061155.GJ2911@vkoul-mobl>
Date:   Mon, 1 Jul 2019 11:41:55 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc:     broonie@...nel.org, robh+dt@...nel.org, devicetree@...r.kernel.org,
        mark.rutland@....com, pierre-louis.bossart@...ux.intel.com,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        bgoswami@...cinc.com
Subject: Re: [RFC PATCH 1/5] dt-bindings: soundwire: add slave bindings

On 11-06-19, 11:40, Srinivas Kandagatla wrote:
> This patch adds bindings for Soundwire Slave devices which includes how
> SoundWire enumeration address is represented in SoundWire slave device
> tree nodes.
> 
> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
> ---
>  .../devicetree/bindings/soundwire/bus.txt     | 48 +++++++++++++++++++
>  1 file changed, 48 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/soundwire/bus.txt
> 
> diff --git a/Documentation/devicetree/bindings/soundwire/bus.txt b/Documentation/devicetree/bindings/soundwire/bus.txt
> new file mode 100644
> index 000000000000..19a672b0d528
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/soundwire/bus.txt

The bindings are for slave right and the file is bus.txt?

> @@ -0,0 +1,48 @@
> +SoundWire bus bindings.
> +
> +SoundWire is a 2-pin multi-drop interface with data and clock line.
> +It facilitates development of low cost, efficient, high performance systems.
> +
> +SoundWire controller bindings are very much specific to vendor.
> +
> +Child nodes(SLAVE devices):
> +Every SoundWire controller node can contain zero or more child nodes
> +representing slave devices on the bus. Every SoundWire slave device is
> +uniquely determined by the enumeration address containing 5 fields:
> +SoundWire Version, Instance ID, Manufacturer ID, Part ID and Class ID
> +for a device. Addition to below required properties, child nodes can
> +have device specific bindings.
> +
> +Required property for SoundWire child node if it is present:
> +- compatible:	 "sdwVER,MFD,PID,CID". The textual representation of
> +		  SoundWire Enumeration address comprising SoundWire
> +		  Version, Manufacturer ID, Part ID and Class ID,
> +		  shall be in lower-case hexadecimal with leading
> +		  zeroes suppressed.
> +		  Version number '0x10' represents SoundWire 1.0
> +		  Version number '0x11' represents SoundWire 1.1
> +		  ex: "sdw10,0217,2010,0"

any reason why we want to code version number and not say sdw,1.0,...
and so on?

> +
> +- sdw-instance-id: Should be ('Instance ID') from SoundWire
> +		  Enumeration Address. Instance ID is for the cases
> +		  where multiple Devices of the same type or Class
> +		  are attached to the bus.

instance id is part of the 48bit device id, so wont it make sense to add
that to compatible as well?

> +
> +SoundWire example for Qualcomm's SoundWire controller:
> +
> +soundwire@...0000 {
> +	compatible = "qcom,soundwire-v1.5.0"
> +	reg = <0x0c2d0000 0x2000>;
> +
> +	spkr_left:wsa8810-left{
> +		compatible = "sdw10,0217,2010,0";
> +		sdw-instance-id = <1>;
> +		...
> +	};
> +
> +	spkr_right:wsa8810-right{
> +		compatible = "sdw10,0217,2010,0";
> +		sdw-instance-id = <2>;
> +		...
> +	};
> +};
> -- 
> 2.21.0

-- 
~Vinod