drivers: base: Introducing software nodes to the firmware node framework

Software node is a new struct fwnode_handle type that can be
used to describe devices in kernel (software). It is meant
to complement fwnodes representing real firmware nodes when
they are incomplete (for example missing device properties)
and to supply the primary fwnode when the firmware lacks
hardware description for a device completely.

The software node type is really meant to replace the
currently used "property_set" struct fwnode_handle type. The
handling of struct property_set is glued to the generic
device property handling code, and it is not possible to
create a struct property_set independently from the device
that it is bind to. struct property_set is only created when
device properties are added to already initialized struct
device, and control of it is only possible from the generic
property handling code.

Software nodes are instead designed to be created
independently from the device entries (struct device). It
makes them much more flexible, as then the device meant to
be bind to the node can be created at a later time, and from
another location. It is also possible to bind multiple
devices to a single software node if needed.

The software node implementation also includes support for
node hierarchy, which was the main motivation for this
commit. The node hierarchy was something that was requested
for the struct property_set, but it did not seem reasonable
to try to extend the property_set support for that purpose.
struct property_set was really meant only for device
property handling like the name suggests.

Support for struct property_set is not yet removed in this
commit, but it will be in the following one.
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Documentation/ABI/testing/sysfs-devices-software_node

+What:		/sys/devices/.../software_node/
+Date:		January 2019
+Contact:	Heikki Krogerus <heikki.krogerus@linux.intel.com>
+Description:
+		This directory contains the details about the device that are
+		assigned in kernel (i.e. software), as opposed to the
+		firmware_node directory which contains the details that are
+		assigned for the device in firmware. The main attributes in the
+		directory will show the properties the device has, and the
+		relationship it has to some of the other devices.

drivers/base/Makefile

@@ -6,7 +6,7 @@ obj-y			:= component.o core.o bus.o dd.o syscore.o \
 			   cpu.o firmware.o init.o map.o devres.o \
 			   attribute_container.o transport_class.o \
 			   topology.o container.o property.o cacheinfo.o \
-			   devcon.o
+			   devcon.o swnode.o
 obj-$(CONFIG_DEVTMPFS)	+= devtmpfs.o
 obj-y			+= power/
 obj-$(CONFIG_ISA_BUS_API)	+= isa.o

drivers/base/core.c

@@ -738,6 +738,10 @@ device_platform_notify(struct device *dev, enum kobject_action action)
 	if (ret)
 		return ret;
 
+	ret = software_node_notify(dev, action);
+	if (ret)
+		return ret;
+
 	if (platform_notify && action == KOBJ_ADD)
 		platform_notify(dev);
 	else if (platform_notify_remove && action == KOBJ_REMOVE)

include/linux/property.h

@@ -311,4 +311,16 @@ fwnode_graph_get_remote_node(const struct fwnode_handle *fwnode, u32 port,
 int fwnode_graph_parse_endpoint(const struct fwnode_handle *fwnode,
 				struct fwnode_endpoint *endpoint);
 
+/* -------------------------------------------------------------------------- */
+/* Software fwnode support - when HW description is incomplete or missing */
+
+bool is_software_node(const struct fwnode_handle *fwnode);
+
+int software_node_notify(struct device *dev, unsigned long action);
+
+struct fwnode_handle *
+fwnode_create_software_node(const struct property_entry *properties,
+			    const struct fwnode_handle *parent);
+void fwnode_remove_software_node(struct fwnode_handle *fwnode);
+
 #endif /* _LINUX_PROPERTY_H_ */