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

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Message-ID: <20190702094510.GO2911@vkoul-mobl>
Date:   Tue, 2 Jul 2019 15:15:10 +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 02-07-19, 09:22, Srinivas Kandagatla wrote:
> Thanks Vinod for taking time to review,
> 
> On 01/07/2019 07:11, Vinod Koul wrote:
> > 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?
> 
> I tried to follow what I have done for SLIMBus.
> Do you prefer them to be documented in slave.txt?

Would that not be better :) We should have a master.txt for bus things

> > > @@ -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?
> 
> For consistency reasons, as other info in hex.
> 
> > 
> > > +
> > > +- 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?
> > 
> So we could have multiple instance of same IP, so adding this to compatible
> string does not make sense! As driver has to list all the possible
> compatible strings.

Yes that makes sense.

-- 
~Vinod