Re: [RFC PATCH 3/3] i2c: i2c-core-of: Handle i2c bus extensions

Herve Codina
2025-02-12T09:45:53Z

Hi Krzysztof,

On Wed, 12 Feb 2025 06:54:19 +0100
Krzysztof Kozlowski <krzk@kernel.org> wrote:

> On 05/02/2025 18:39, Herve Codina wrote:
> >
> > dev_dbg(&adap->dev, "of_i2c: walking child nodes from %pOF\n", bus);
> >
> > - /* Register device directly attached to this bus */
> > + /*
> > + * Register device directly described in this bus node before looking
> > + * at extensions.
> > + */
> > for_each_available_child_of_node(bus, node) {
> > + /* Filter out extension node */
> > + if (of_node_name_eq(node, "i2c-bus-extension"))
>
> Where is the ABI documented?
>
> > + continue;
> > +
> > if (of_node_test_and_set_flag(node, OF_POPULATED))
> > continue;
> >
> > @@ -103,6 +110,23 @@ static void of_i2c_register_children(struct i2c_adapter *adap,
> > of_node_clear_flag(node, OF_POPULATED);
> > }
> > }
> > +
> > + /* Look at extensions */
> > + for_each_available_child_of_node(bus, node) {
> > + if (!of_node_name_eq(node, "i2c-bus-extension"))
> > + continue;
> > +
> > + extension = of_parse_phandle(node, "i2c-bus", 0);
>
> And this?
>
> > + if (!extension)
> > + continue;
> > +

I know the binding is not present in this RFC series.

As I mentioned in my cover letter, the binding that needs to be updated is
available in dt-schema repo [0].

When the binding is be accepted in dt-schema repo, I will not be able to
change it and because two repos are involved, I cannot send the binding and
the implementation in the same series.

Before sending a patch to update the binding in dt-schema repo, I would
like first to discuss the proposed i2c bus extension idea in terms of:
1) DT properties naming and purpose
2) implementation

[0] https://github.com/devicetree-org/dt-schema/blob/main/dtschema/schemas/i2c/i2c-controller.yaml

Best regards,
Hervé