linux-kernel - Re: [PATCH v3 1/9] dt-bindings: misc: Describe TI FPC202 dual port controller

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <2072150.UuDqf3iUMg@fw-rgant>
Date: Tue, 26 Nov 2024 09:05:42 +0100
From: Romain Gantois <romain.gantois@...tlin.com>
To: Conor Dooley <conor@...nel.org>
Cc: Wolfram Sang <wsa+renesas@...g-engineering.com>,
 Tomi Valkeinen <tomi.valkeinen@...asonboard.com>,
 Luca Ceresoli <luca.ceresoli@...tlin.com>,
 Andi Shyti <andi.shyti@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>,
 Derek Kiernan <derek.kiernan@....com>, Dragan Cvetic <dragan.cvetic@....com>,
 Arnd Bergmann <arnd@...db.de>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Mauro Carvalho Chehab <mchehab@...nel.org>,
 Linus Walleij <linus.walleij@...aro.org>,
 Bartosz Golaszewski <brgl@...ev.pl>,
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
 Kory Maincent <kory.maincent@...tlin.com>, linux-i2c@...r.kernel.org,
 linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
 linux-media@...r.kernel.org, linux-gpio@...r.kernel.org
Subject:
 Re: [PATCH v3 1/9] dt-bindings: misc: Describe TI FPC202 dual port controller

Hello Conor,

On lundi 25 novembre 2024 19:26:35 heure normale d’Europe centrale Conor Dooley wrote:
> On Mon, Nov 25, 2024 at 09:45:15AM +0100, Romain Gantois wrote:
> > The FPC202 dual port controller serves as a low speed signal aggregator
> > for
...
> > +
> > +required:
> > +  - compatible
> > +  - gpio-controller
> > +  - "#gpio-cells"
> > +  - reg
> > +  - "#address-cells"
> > +  - "#size-cells"
> > +  - i2c@0
> > +  - i2c@1
> 
> btw, why are both downstream ports required?

It's because both downstream ports are always present in an FPC202 unit
so in my opinion, it doesn't make sense to describe an FPC202 with only one
downstream port.

I suppose you could also consider that ports would only be described in the DT
if they were connected to something in the hardware, but I don't think it would
make sense to use an FPC202 in this way. After all, the whole point of this
component is to act as an I2C ATR and low-speed signal aggregator for
downstream devices which would have address collisions if you placed them
on the same I2C bus.

But then again, you could consider that DT bindings should only describe what is
possible, and not only what makes sense as a use case. I don't really know how to
answer this question myself, so I'll refer to the maintainers' opinions.

Best Regards,

-- 
Romain Gantois, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com