driver core: fw_devlink: Add fw_devlink_count_absent_consumers()

Some platforms have power domains that are active on boot and must
remain powered up until all of their consumers probe. The genpd core
needs a way to count how many consumers haven't probed yet to avoid
powering off such domains.

Add a fw_devlink_count_absent_consumers() function, which returns the
total count of consumer devices which either have not been created at
all yet (only fwlinks exist) or have been created but have no driver
bound and fully probed yet.

Signed-off-by: Hector Martin <marcan@marcan.st>

Author: marcan

drivers/base/core.c

@@ -2344,6 +2344,32 @@ static void fw_devlink_link_device(struct device *dev)
 	mutex_unlock(&fwnode_link_lock);
 }
 
+/**
+ * fw_devlink_count_absent_consumers - Return how many consumers have
+ * either not been created yet, or do not yet have a driver attached.
+ * @fwnode: fwnode of the supplier
+ */
+int fw_devlink_count_absent_consumers(struct fwnode_handle *fwnode)
+{
+	struct fwnode_link *link, *tmp;
+	struct device_link *dlink, *dtmp;
+	struct device *sup_dev = get_dev_from_fwnode(fwnode);
+	int count = 0;
+
+	list_for_each_entry_safe(link, tmp, &fwnode->consumers, s_hook)
+		count++;
+
+	if (!sup_dev)
+		return count;
+
+	list_for_each_entry_safe(dlink, dtmp, &sup_dev->links.consumers, s_node)
+		if (dlink->consumer->links.status != DL_DEV_DRIVER_BOUND)
+			count++;
+
+	return count;
+}
+EXPORT_SYMBOL_GPL(fw_devlink_count_absent_consumers);
+
 /* Device links support end. */
 
 int (*platform_notify)(struct device *dev) = NULL;

include/linux/fwnode.h

@@ -221,5 +221,6 @@ int fwnode_link_add(struct fwnode_handle *con, struct fwnode_handle *sup,
 void fwnode_links_purge(struct fwnode_handle *fwnode);
 void fw_devlink_purge_absent_suppliers(struct fwnode_handle *fwnode);
 bool fw_devlink_is_strict(void);
+int fw_devlink_count_absent_consumers(struct fwnode_handle *fwnode);
 
 #endif