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

["Rob Herring (Arm)" <robh@kernel.org>]

On Sat, 15 Aug 2026 20:33:13 -0700, Abdurrahman Hussain 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@nexthop.ai>
> ---
> 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@nexthop.ai
> 
> 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
>   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@nexthop.ai
> 
> To: Rob Herring <robh@kernel.org>
> To: Saravana Kannan <saravanak@kernel.org>
> Cc: devicetree@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> ---
>  drivers/of/property.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 

Applied, thanks!