[alsa-devel] [PATCH v2 02/12] device: property: find dependencies of a firmware node

[Tomeu Vizoso]

Adds API that allows callers to find out what other firmware nodes a
node depends on.

Implementors of bindings documentation can register callbacks that
return the dependencies of a node.

Dependency information can be used to change the order in which devices
are probed, or to print a warning when a device node is going to be
probed without all its dependencies fulfilled.

Signed-off-by: Tomeu Vizoso <tomeu.vizoso at collabora.com>
---

Changes in v2:
- Allow bindings implementations register a function instead of using
  class callbacks, as not only subsystems implement firmware bindings.

 drivers/base/property.c  | 91 ++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/fwnode.h   |  5 +++
 include/linux/property.h | 12 +++++++
 3 files changed, 108 insertions(+)

diff --git a/drivers/base/property.c b/drivers/base/property.c
index 8ead1ba..9d38ede 100644
--- a/drivers/base/property.c
+++ b/drivers/base/property.c
@@ -19,7 +19,13 @@
 #include <linux/platform_device.h>
 #include <linux/property.h>
 
+struct dependency_parser {
+	struct list_head parser;
+	void (*func)(struct fwnode_handle *fwnode, struct list_head *deps);
+};
+
 static bool fwnode_match_enable = false;
+static LIST_HEAD(dependency_parsers);
 
 /**
  * device_add_property_set - Add a collection of properties to a device object.
@@ -553,6 +559,27 @@ bool device_dma_is_coherent(struct device *dev)
 EXPORT_SYMBOL_GPL(device_dma_is_coherent);
 
 /**
+ * fwnode_add_dependency - add firmware node to the passed dependency list
+ * @fwnode: Firmware node to add to dependency list
+ * @list: Dependency list to add the fwnode to
+ */
+void fwnode_add_dependency(struct fwnode_handle *fwnode,
+			   struct list_head *list)
+{
+	struct fwnode_dependency *dep;
+
+	dep = kzalloc(sizeof(*dep), GFP_KERNEL);
+	if (!dep)
+		return;
+
+	INIT_LIST_HEAD(&dep->dependency);
+	dep->fwnode = fwnode;
+
+	list_add_tail(&dep->dependency, list);
+}
+EXPORT_SYMBOL_GPL(fwnode_add_dependency);
+
+/**
  * fwnode_get_parent - return the parent node of a device node
  * @fwnode: Device node to find the parent node of
  */
@@ -600,6 +627,70 @@ bool fwnode_is_compatible(struct fwnode_handle *fwnode, const char *compatible)
 EXPORT_SYMBOL_GPL(fwnode_is_compatible);
 
 /**
+ * fwnode_add_dependency_parser - register dependency parser
+ * @func: Function that will be called to find out dependencies of a node
+ *
+ * Registers a callback that will be called when collecting the dependencies
+ * of a firmware node. The callback should inspect the properties of the node
+ * and call fwnode_add_dependency() for each dependency it recognizes, from
+ * the bindings documentation.
+ */
+void fwnode_add_dependency_parser(
+	void (*func)(struct fwnode_handle *fwnode, struct list_head *deps))
+{
+	struct dependency_parser *parser;
+
+	parser = kzalloc(sizeof(*parser), GFP_KERNEL);
+	if (!parser)
+		return;
+
+	INIT_LIST_HEAD(&parser->parser);
+	parser->func = func;
+
+	list_add_tail(&parser->parser, &dependency_parsers);
+}
+EXPORT_SYMBOL_GPL(fwnode_add_dependency_parser);
+
+/**
+ * fwnode_remove_dependency_parser - unregister dependency parser
+ * @func: Function that was to be called to find out dependencies of a node
+ */
+void fwnode_remove_dependency_parser(
+	void (*func)(struct fwnode_handle *fwnode, struct list_head *deps))
+{
+	struct dependency_parser *parser, *tmp;
+
+	list_for_each_entry_safe(parser, tmp, &dependency_parsers, parser) {
+		if (parser->func == func) {
+			list_del(&parser->parser);
+			kfree(parser);
+			return;
+		}
+	}
+}
+EXPORT_SYMBOL_GPL(fwnode_remove_dependency_parser);
+
+/**
+ * fwnode_get_dependencies - find out what dependencies a firmware node has
+ * @fwnode: firmware node to find its dependencies
+ * @deps: list of struct fwnode_dependency in which dependencies will be placed
+ */
+void fwnode_get_dependencies(struct fwnode_handle *fwnode,
+			     struct list_head *deps)
+{
+	struct dependency_parser *parser;
+	struct fwnode_handle *child;
+
+	list_for_each_entry(parser, &dependency_parsers, parser)
+		parser->func(fwnode, deps);
+
+	/* Some device nodes will have dependencies in non-device sub-nodes */
+	fwnode_for_each_child_node(fwnode, child)
+		if (!fwnode_property_present(child, "compatible"))
+			fwnode_get_dependencies(child, deps);
+}
+
+/**
  * fwnode_driver_match_device - Tell if a driver matches a device.
  * @drv: the device_driver structure to test
  * @dev: the device structure to match against
diff --git a/include/linux/fwnode.h b/include/linux/fwnode.h
index 0408545..68ab558 100644
--- a/include/linux/fwnode.h
+++ b/include/linux/fwnode.h
@@ -24,4 +24,9 @@ struct fwnode_handle {
 	struct fwnode_handle *secondary;
 };
 
+struct fwnode_dependency {
+	struct fwnode_handle *fwnode;
+	struct list_head dependency;
+};
+
 #endif
diff --git a/include/linux/property.h b/include/linux/property.h
index 4e453c4..b8b86ea 100644
--- a/include/linux/property.h
+++ b/include/linux/property.h
@@ -86,6 +86,18 @@ bool fwnode_is_compatible(struct fwnode_handle *fwnode, const char *compatible);
 bool fwnode_driver_match_device(struct device *dev,
 				const struct device_driver *drv);
 
+void fwnode_add_dependency(struct fwnode_handle *fwnode,
+			   struct list_head *list);
+
+void fwnode_add_dependency_parser(
+	void (*func)(struct fwnode_handle *fwnode, struct list_head *deps));
+
+void fwnode_remove_dependency_parser(
+	void (*func)(struct fwnode_handle *fwnode, struct list_head *deps));
+
+void fwnode_get_dependencies(struct fwnode_handle *fwnode,
+			     struct list_head *list);
+
 unsigned int device_get_child_node_count(struct device *dev);
 
 static inline bool device_property_read_bool(struct device *dev,
-- 
2.4.1