Re: [PATCH 1/4] dt-bindings: usb-connector: Add support for Type-C alternate-modes

From: Prashant Malani <pmalani@chromium.org>
To: Rob Herring <robh@kernel.org>
Cc: Hans de Goede <hdegoede@redhat.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Guenter Roeck <linux@roeck-us.net>,
	Heikki Krogerus <heikki.krogerus@linux.intel.com>,
	Tobias Schramm <t.schramm@manjaro.org>,
	"open list:USB NETWORKING DRIVERS" <linux-usb@vger.kernel.org>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
	<devicetree@vger.kernel.org>
Subject: Re: [PATCH 1/4] dt-bindings: usb-connector: Add support for Type-C alternate-modes
Date: Mon, 20 Jul 2020 22:49:00 -0700	[thread overview]
Message-ID: <CACeCKacEqZX5FKF2Gpaa_zEgf-sCrxsgk-WJ9VDdYsrwZNoCBg@mail.gmail.com> (raw)
In-Reply-To: <20200721022610.GA3391383@bogus>

HI Rob,

On Mon, Jul 20, 2020 at 7:26 PM Rob Herring <robh@kernel.org> wrote:
>
> On Tue, Jul 14, 2020 at 01:36:14PM +0200, Hans de Goede wrote:
> > This commit adds the minimum bindings required to allow describing which
> > altmodes a port supports. Currently this is limited to just specifying:
> >
> > 1. The svid, which is the id of the altmode, e.g. displayport altmode has
> > a svid of 0xff01.
> >
> > 2. The vdo, a 32 bit integer, typically used as a bitmask describing the
> > capabilities of the altmode, the bits in the vdo are specified in the
> > specification of the altmode, the dt-binding simply refers to the
> > specification as that is the canonical source of the meaning of the bits.
>
> What if this information should be derived from information already in
> DT (or would be there if alt mode connections are described)?
>
> >
> > Later on we may want to extend the binding with extra properties specific
> > to some altmode, but for now this is sufficient to e.g. hook up
> > displayport alternate-mode.
>
> I don't think this is sufficient as it doesn't describe how alternate
> modes are connected to various components. This has been discussed some
> here[1] with the CrOS folks. Maybe this is orthogonal, IDK, but I really
> need something that is somewhat complete and not sprinkle a few new
> properties at a time.

Just thought I'd add a link[2] to some amendments which were made to
the "switch"
proposal in the thread you added a link to (it has many responses, so
not sure if my
responses got lost in the thread). I also wrote a short summary[3].

Please ignore these if you've already taken a look at them :)

Best regards,

-Prashant

[2] https://lkml.org/lkml/2020/6/12/602
[3] https://lkml.org/lkml/2020/7/10/234
>
> > Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> > ---
> > Note I hope I got the yaml correct, this is my first time writing a
> > dt-binding in the new yaml style. I did run:
> > make dt_binding_check DT_SCHEMA_FILES=Documentation/devicetree/bindings/connector/usb-connector.yaml
> > and that was happy.
>
> That aspect of it looks fine.
>
> Rob
>
> [1] https://lkml.org/lkml/2020/4/22/1819
>