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

[Rob Herring <robh@kernel.org>]

On Sun, Aug 16, 2026 at 10:17:08PM -0700, Saravana Kannan wrote:
> On Sat, Aug 15, 2026 at 8:33 PM Abdurrahman Hussain
> <abdurrahman@nexthop.ai> 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
> 
> 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?

sashiko has configuration for who to reply to rather than reply-all. 
Probably something not right there. 

I think it should be reply-all, but the sashiko maintainers are 
reluctant to enable that and some folks don't want to get the reports.

Rob