linux-kernel - Re: [PATCH v3 1/1] schemas: i2c: Introduce I2C bus extensions

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: <CAL_JsqJ=jmXVwjtNCjRpUKj02dnJEz4GHMX2wMRaWw=M+sZQ0w@mail.gmail.com>
Date: Fri, 1 Aug 2025 13:09:54 -0500
From: Rob Herring <robh@...nel.org>
To: Herve Codina <herve.codina@...tlin.com>
Cc: Ayush Singh <ayush@...gleboard.org>, Wolfram Sang <wsa+renesas@...g-engineering.com>, 
	Andi Shyti <andi.shyti@...nel.org>, Krzysztof Kozlowski <krzk@...nel.org>, 
	Conor Dooley <conor+dt@...nel.org>, linux-i2c@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, devicetree-spec@...r.kernel.org, 
	Luca Ceresoli <luca.ceresoli@...tlin.com>, Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v3 1/1] schemas: i2c: Introduce I2C bus extensions

On Wed, Jun 18, 2025 at 3:23 AM Herve Codina <herve.codina@...tlin.com> wrote:
>
> An I2C bus can be wired to the connector and allows an add-on board to
> connect additional I2C devices to this bus.
>
> Those additional I2C devices could be described as sub-nodes of the I2C
> bus controller node however for hotplug connectors described via device
> tree overlays there is additional level of indirection, which is needed
> to decouple the overlay and the base tree:
>
>   --- base device tree ---
>
>   i2c1: i2c@...d0000 {
>       compatible = "xyz,foo";
>       i2c-bus-extension@0 {

This is at I2C bus address 0? No. You are mixing 2 different address
spaces. Don't do that.

You could solve this with just a property in the parent. If there's
more than 1, then it's just multiple phandles. However I don't think
you need this at all. You can just search the DT for 'i2c-parent' and
find phandles that match the i2c controller node. But why does the
controller driver need to know about connectors? Shouldn't the
connector driver drive this and tell the controller there's more
devices?

Rob