linux-kernel - Re: [PATCH 01/14] Documentation: Add SoundWire summary

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Date:   Sat, 21 Oct 2017 16:58:40 +0530
From:   Vinod Koul <vinod.koul@...el.com>
To:     Mark Brown <broonie@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        ALSA <alsa-devel@...a-project.org>, Takashi <tiwai@...e.de>,
        Pierre <pierre-louis.bossart@...ux.intel.com>,
        Sanyog Kale <sanyog.r.kale@...el.com>,
        Shreyas NC <shreyas.nc@...el.com>, patches.audio@...el.com,
        alan@...ux.intel.com,
        Charles Keepax <ckeepax@...nsource.cirrus.com>,
        Sagar Dharia <sdharia@...eaurora.org>,
        srinivas.kandagatla@...aro.org, plai@...eaurora.org,
        Sudheer Papothi <spapothi@...eaurora.org>
Subject: Re: [PATCH 01/14] Documentation: Add SoundWire summary

On Sat, Oct 21, 2017 at 09:57:44AM +0100, Mark Brown wrote:
> On Thu, Oct 19, 2017 at 08:33:17AM +0530, Vinod Koul wrote:
> 
> > +The SoundWire protocol supports up to eleven Slave interfaces. All the
> 
> There's lots of perfectly normal nouns in this document like Slave here
> which are randomly capitalized.  Is there some great reason for this?
> It makes the document pretty distracting to read.

Slave, SoundWire etc are MIPI definitions hence capitalized.

> > +Bus implements API to read standard Master MIPI properties and also provides
> > +callback in Master ops for Master driver to implement own functions that
> 
> implement it's own functions.

ok

> 
> > +provides capabilities information. DT support is not implemented at this
> > +time but should be trivial to add since capabilities are enabled with the
> > +device_property_ API.
> 
> Since we're making this up from whole cloth rather than following an
> existing standard let's get a DT binding document together and review
> the properties that are getting defined.

I don't have a DT to test, but looking at Slimbus code I guess assumptions
are fair and we seem to have similar concepts and implementation.

> 
> > +	/* Check ACPI for Slave devices */
> > +        sdw_acpi_find_slaves(bus);
> 
> Tab/space issues here.

fixed now

> 
> > +The MIPI specification requires each Slave interface to expose a unique
> > +48-bit identifier, stored in 6 read only dev_id registers. This dev_id
> > +identifier contains vendor and part information, as well as a field enabling
> > +to differentiate between identical components. An additional class field is
> > +currently unused. Slave driver is written for the specific 48-bit
> > +identifier, Bus enumerates the Slave device based on the 48-bit identifier.
> 
> So this says that the instance identifer is part of the device
> identifier but the driver should bind to the whole device identifer?
> I'd expect the driver to bind to everything except the instance
> identifer.

Other parts are still TBD and not really used, like Device Class, Spec
version. We are using only mfg id and part id for binding.

-- 
~Vinod