Quoting Greg Kroah-Hartman (2019-10-04 08:37:50)
> On Wed, Sep 11, 2019 at 03:29:25AM -0700, Stephen Boyd wrote:
> > Quoting Saravana Kannan (2019-09-04 14:11:22)
> > > + int ret = 0;
> > > + struct device_node *tmp_np = sup_np;
> > > +
> > > + of_node_get(sup_np);
> > > + /*
> > > + * Find the device node that contains the supplier phandle. It may be
> > > + * @sup_np or it may be an ancestor of @sup_np.
> > > + */
> > > + while (sup_np && !of_find_property(sup_np, "compatible", NULL))
> > > + sup_np = of_get_next_parent(sup_np);
> >
> > I don't get this. This is assuming that drivers are only probed for
> > device nodes that have a compatible string? What about drivers that make
> > sub-devices for clk support that have drivers in drivers/clk/ that then
> > attach at runtime later? This happens sometimes for MFDs that want to
> > split the functionality across the driver tree to the respective
> > subsystems.
>
> For that, the link would not be there, correct?
The parent device (MFD) would have the links because that is the device
node with the provider property like '#clock-cells'. The child clk
device that's populated by the MFD would be the one actually providing
the clk via a driver that may probe any time later, or never, depending
on if the clk driver is configured as a module or not. I fail to see how
this will work for these cases.
Is this logic there to find the parent of a regulator phandle and match
that to some driver? It looks like it.
>
> > > +static int of_link_property(struct device *dev, struct device_node *con_np,
> > > + const char *prop_name)
> > > +{
> > > + struct device_node *phandle;
> > > + const struct supplier_bindings *s = bindings;
> > > + unsigned int i = 0;
> > > + bool matched = false;
> > > + int ret = 0;
> > > +
> > > + /* Do not stop at first failed link, link all available suppliers. */
> > > + while (!matched && s->parse_prop) {
> > > + while ((phandle = s->parse_prop(con_np, prop_name, i))) {
> > > + matched = true;
> > > + i++;
> > > + if (of_link_to_phandle(dev, phandle) == -EAGAIN)
> > > + ret = -EAGAIN;
> >
> > And don't break?
>
> There was comments before about how this is not needed. Frank asked
> that the comment be removed. And now you point it out again :)
>
> Look at the comment a few lines up, we have to go through all of the
> suppliers.
>
Ok. The comment tells me what is happening but it misses the essential
part which is _why_ we must make links to each supplier and return
-EAGAIN.
