linux-kernel - Re: [PATCH v3 05/11] dt-bindings: i3c: Document core bindings

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Date:   Wed, 28 Mar 2018 19:28:07 +0200
From:   Boris Brezillon <boris.brezillon@...tlin.com>
To:     Rob Herring <robh@...nel.org>
Cc:     Wolfram Sang <wsa@...-dreams.de>,
        Linux I2C <linux-i2c@...r.kernel.org>,
        Jonathan Corbet <corbet@....net>, linux-doc@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Przemyslaw Sroka <psroka@...ence.com>,
        Arkadiusz Golec <agolec@...ence.com>,
        Alan Douglas <adouglas@...ence.com>,
        Bartosz Folta <bfolta@...ence.com>,
        Damian Kos <dkos@...ence.com>,
        Alicja Jurasik-Urbaniak <alicja@...ence.com>,
        Cyprian Wronka <cwronka@...ence.com>,
        Suresh Punnoose <sureshp@...ence.com>,
        Rafal Ciepiela <rafalc@...ence.com>,
        Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
        Nishanth Menon <nm@...com>, Pawel Moll <pawel.moll@....com>,
        Mark Rutland <mark.rutland@....com>,
        Ian Campbell <ijc+devicetree@...lion.org.uk>,
        Kumar Gala <galak@...eaurora.org>, devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Vitor Soares <Vitor.Soares@...opsys.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Xiang Lin <Xiang.Lin@...aptics.com>,
        linux-gpio@...r.kernel.org,
        Boris Brezillon <boris.brezillon@...e-electrons.com>
Subject: Re: [PATCH v3 05/11] dt-bindings: i3c: Document core bindings

On Wed, 28 Mar 2018 11:42:07 -0500
Rob Herring <robh@...nel.org> wrote:


> >>  
> >> > +where device-type is describing the type of device connected on the bus
> >> > +(gpio-controller, sensor, ...).
> >> > +
> >> > +Required properties
> >> > +-------------------
> >> > +- reg: contains 3 cells
> >> > +  + first cell : encodes the I2C address. Should be 0 if the device does not
> >> > +            have one (0 is not a valid I3C address).  
> >>
> >> Change here to "encodes the static I2C address".
> >>
> >> 0 is not a valid I2C address?  
> >
> > According to [1] it is reserved, and it's reserved in the I3C spec
> > anyway (see "Table 9 I3C Slave Address Restrictions" in the I3C spec).  
> 
> Sorry, what I meant was s/I3C/I2C/. The first cell is I2C address and
> 0 is not valid.

Okay, got it now :-).
> 
> >> > +
> >> > +  + second and third cells: should encode the ProvisionalID. The second cell
> >> > +                       contains the manufacturer ID left-shifted by 1.
> >> > +                       The third cell contains ORing of the part ID
> >> > +                       left-shifted by 16, the instance ID left-shifted
> >> > +                       by 12 and the extra information. This encoding is
> >> > +                       following the PID definition provided by the I3C
> >> > +                       specification.  
> >
> > One extra question for you: should I refer to the I3C_DEV(),
> > I3C_DEV_WITH_STATIC_ADDR() and I2C_DEV() macros in the bindings doc?
> > And if I do, should I use them my example?  
> 
> Well, I don't want to see "device@..._DEV(...)" for unit-addresses.

That wouldn't work anyway.

> You can use them for reg property, but it's somewhat pointless to use
> it in one place and not the other.

Not sure I follow you. These macros have been added to ease definitions
of reg, but you'll still have to manually define the unit-address
manually. Are you saying I should not use them in dts files or just that
I should not mention it in the doc. If this is the former, then patch 6
should be dropped.

-- 
Boris Brezillon, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com