Re: [PATCH v3] of: property: add i2c-parent to fw_devlink supplier bindings

[Saravana Kannan]

On Sat, Aug 15, 2026 at 8:33 PM Abdurrahman Hussain
<abdurrahman@xxxxxxxxxx> wrote:
>
> Platform-device i2c muxes (i2c-mux-reg, i2c-mux-gpio, ...) reference
> the bus they multiplex with an i2c-parent phandle and hold a reference
> on that adapter from probe until remove. Unlike muxes that are clients
> on the parent bus, they live outside the adapter's device hierarchy,
> so nothing orders their teardown against it: if the adapter's device
> is unbound first — e.g. while reverting a device-tree overlay whose
> changeset attached the mux nodes before the controller nodes —
> i2c_del_adapter() blocks forever in
> wait_for_completion(&adap->dev_released), waiting for a reference that
> is only dropped later in the same teardown sequence.
>
> Teach fw_devlink about i2c-parent so the core creates the
> corresponding device links: consumers are unbound before the parent
> adapter's device, and probe ordering no longer needs -EPROBE_DEFER.
>
> A plain DEFINE_SIMPLE_PROP() cannot be used because the property has
> two incompatible layouts: the i2c mux bindings hold a list of bare
> phandles (i2c-demux-pinctrl takes several), while toshiba,tc9563 holds
> a single phandle followed by an i2c slave-address cell. The two forms
> are indistinguishable in the flattened tree, and a 0-cell parse of the
> tc9563 form would read the slave address as a phandle, linking the
> consumer to whatever node happens to carry that phandle value. Use a
> custom parser that only takes entry 0 for toshiba,tc9563 nodes.
>
> Signed-off-by: Abdurrahman Hussain <abdurrahman@xxxxxxxxxx>
> ---
> Changes in v3:
> - Fix the tc9563 compatible check: match "pci1179,0623" (the actual
>   binding compatible) instead of "toshiba,tc9563", which never matched
>   and let the bare-phandle parser misread the i2c slave-address cell as
>   a phandle (Sashiko AI review)
> - Link to v2: https://patch.msgid.link/20260815-b4-of-property-add-i2c-parent-v2-1-239c6da9e097@xxxxxxxxxx
>
> Changes in v2:
> - Use a custom parser instead of DEFINE_SIMPLE_PROP: toshiba,tc9563 puts
>   an i2c slave-address cell after the phandle, which a 0-cell parse
>   would misread as a phandle (Sashiko AI review, Rob). Kept the full

A bit of a tangent, is this a bug in Sashiko bot?
It just dropped me from the reply in the v1 patch set. Any idea why?

-Saravana

>   phandle-list parse for other users since i2c-demux-pinctrl takes
>   several parents; only tc9563 is limited to entry 0
> - Move the Signed-off-by into the commit message proper; v1 had it below
>   the '---' cutter line where it would be dropped on apply
> - Link to v1: https://patch.msgid.link/20260813-b4-of-property-add-i2c-parent-v1-1-a2487e920ce1@xxxxxxxxxx
>
> To: Rob Herring <robh@xxxxxxxxxx>
> To: Saravana Kannan <saravanak@xxxxxxxxxx>
> Cc: devicetree@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> ---
>  drivers/of/property.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
>
> diff --git a/drivers/of/property.c b/drivers/of/property.c
> index 72cf12907de0..9bf3bc0a5f38 100644
> --- a/drivers/of/property.c
> +++ b/drivers/of/property.c
> @@ -1471,6 +1471,22 @@ static struct device_node *parse_gpio_compat(struct device_node *np,
>         return sup_args.np;
>  }
>
> +static struct device_node *parse_i2c_parent(struct device_node *np,
> +                                           const char *prop_name, int index)
> +{
> +       if (strcmp(prop_name, "i2c-parent"))
> +               return NULL;
> +
> +       /* tc9563 (pci1179,0623) is <phandle addr>; every other user is bare phandles */
> +       if (of_device_is_compatible(np, "pci1179,0623")) {
> +               if (index)
> +                       return NULL;
> +               return of_parse_phandle(np, prop_name, 0);
> +       }
> +
> +       return of_parse_phandle(np, prop_name, index);
> +}
> +
>  static struct device_node *parse_interrupts(struct device_node *np,
>                                             const char *prop_name, int index)
>  {
> @@ -1562,6 +1578,7 @@ static const struct supplier_bindings of_supplier_bindings[] = {
>         { .parse_prop = parse_resets, },
>         { .parse_prop = parse_leds, },
>         { .parse_prop = parse_backlight, },
> +       { .parse_prop = parse_i2c_parent, },
>         { .parse_prop = parse_panel, },
>         { .parse_prop = parse_msi_parent, },
>         { .parse_prop = parse_pses, },
>
> ---
> base-commit: d58772d8520c7ef247c4b95c9bd76d3a25da9ff5
> change-id: 20260813-b4-of-property-add-i2c-parent-168c6d7f1934
>
> Best regards,
> --
> Abdurrahman Hussain <abdurrahman@xxxxxxxxxx>
>