Re: [PATCH v3 03/10] software node: allow referencing firmware nodes

Andy Shevchenko
2025-10-31T08:24:00Z

On Thu, Oct 30, 2025 at 04:17:48AM -0700, Bartosz Golaszewski wrote:
> On Thu, 30 Oct 2025 10:41:39 +0100, Andy Shevchenko
> <andriy.shevchenko@linux.intel.com> said:
> > On Wed, Oct 29, 2025 at 01:28:37PM +0100, Bartosz Golaszewski wrote:
> >>
> >> At the moment software nodes can only reference other software nodes.
> >> This is a limitation for devices created, for instance, on the auxiliary
> >> bus with a dynamic software node attached which cannot reference devices
> >> the firmware node of which is "real" (as an OF node or otherwise).
> >>
> >> Make it possible for a software node to reference all firmware nodes in
> >> addition to static software nodes. To that end: add a second pointer to
> >> struct software_node_ref_args of type struct fwnode_handle. The core
> >> swnode code will first check the swnode pointer and if it's NULL, it
> >> will assume the fwnode pointer should be set. Rework the helper macros
> >> and deprecate the existing ones whose names don't indicate the reference
> >> type.
> >>
> >> Software node graphs remain the same, as in: the remote endpoints still
> >> have to be software nodes.
> >
> > ...
> >
> >> -#define SOFTWARE_NODE_REFERENCE(_ref_, ...) \
> >> +#define __SOFTWARE_NODE_REF(_ref, _node, ...) \
> >> (const struct software_node_ref_args) { \
> >> - .node = _ref_, \
> >> + ._node = _ref, \
> >> .nargs = COUNT_ARGS(__VA_ARGS__), \
> >> .args = { __VA_ARGS__ }, \
> >> }
> >
> > Okay, looking at this again I think we don't need a new parameter.
> > We may check the type of _ref_
> > (actually why are the macro parameters got renamed here and elsewhere?)
> > and assign the correct one accordingly. I think this is what _Generic()
> > is good for.
> >
>
> Oh, that's neat, I would love to use _Generic() here but I honest to god have
> no idea how to make it work. I tried something like:
>
> #define __SOFTWARE_NODE_REF(_ref, ...) \
> _Generic(_ref, \
> const struct software_node *: \
> (const struct software_node_ref_args) { \
> .swnode = _ref, \
> .nargs = COUNT_ARGS(__VA_ARGS__), \
> .args = { __VA_ARGS__ }, \
> }, \
> struct fwnode_handle *: \
> (const struct software_node_ref_args) { \
> .fwnode = _ref, \
> .nargs = COUNT_ARGS(__VA_ARGS__), \
> .args = { __VA_ARGS__ }, \
> } \
> )
>
>
> But this fails like this:
>
> In file included from ./include/linux/acpi.h:16,
> from drivers/reset/core.c:8:
> drivers/reset/core.c: In function ‘__reset_add_reset_gpio_device’:
> drivers/reset/core.c:958:52: error: initialization of ‘const struct
> software_node *’ from incompatible pointer type ‘struct fwnode_handle
> *’ [-Wincompatible-pointer-types]
> 958 | parent->fwnode,
> | ^~~~~~
> ./include/linux/property.h:374:35: note: in definition of macro
> ‘__SOFTWARE_NODE_REF’
> 374 | .swnode = _ref, \
>
> So the right branch is not selected. How exactly would you use it here?

I believe this is an easy task.

But first of all, your series doesn't compile AFAICS:

drivers/reset/core.c:981:6: error: variable 'ret' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
981 | if (IS_ERR(rgpio_dev->swnode))
| ^~~~~~~~~~~~~~~~~~~~~~~~~
drivers/reset/core.c:1001:9: note: uninitialized use occurs here
1001 | return ret;
| ^~~
drivers/reset/core.c:981:2: note: remove the 'if' if its condition is always false
981 | if (IS_ERR(rgpio_dev->swnode))
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
982 | goto err_put_of_node;
| ~~~~~~~~~~~~~~~~~~~~
drivers/reset/core.c:905:13: note: initialize the variable 'ret' to silence this warning
905 | int id, ret, lflags;
| ^
| = 0
1 error generated.

So, but to the topic

I have applied this and get the only error as per above

(const struct software_node_ref_args) { \
- ._node = _ref, \
+ .swnode = _Generic(_ref, const struct software_node *: _ref, default: NULL), \
+ .fwnode = _Generic(_ref, struct fwnode_handle *: _ref, default: NULL), \

--
With Best Regards,
Andy Shevchenko