dt: add of_alias_scan and of_alias_get_id

The patch adds function of_alias_scan to populate a global lookup
table with the properties of 'aliases' node and function
of_alias_get_id for drivers to find alias id from the lookup table.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
[grant.likely: add locking and rework parse loop]
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

2 files changed, 133 insertions, 1 deletions

diff --git a/drivers/of/base.c b/drivers/of/base.c
index 3ff22e3..fb28b5a 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -17,14 +17,39 @@
  *      as published by the Free Software Foundation; either version
  *      2 of the License, or (at your option) any later version.
  */
+#include <linux/ctype.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/spinlock.h>
 #include <linux/slab.h>
 #include <linux/proc_fs.h>
 
+/**
+ * struct alias_prop - Alias property in 'aliases' node
+ * @link:	List node to link the structure in aliases_lookup list
+ * @alias:	Alias property name
+ * @np:		Pointer to device_node that the alias stands for
+ * @id:		Index value from end of alias name
+ * @stem:	Alias string without the index
+ *
+ * The structure represents one alias property of 'aliases' node as
+ * an entry in aliases_lookup list.
+ */
+struct alias_prop {
+	struct list_head link;
+	const char *alias;
+	struct device_node *np;
+	int id;
+	char stem[0];
+};
+
+static LIST_HEAD(aliases_lookup);
+
 struct device_node *allnodes;
 struct device_node *of_chosen;
+struct device_node *of_aliases;
+
+static DEFINE_MUTEX(of_aliases_mutex);
 
 /* use when traversing tree through the allnext, child, sibling,
  * or parent members of struct device_node.
@@ -988,3 +1013,108 @@ out_unlock:
 }
 #endif /* defined(CONFIG_OF_DYNAMIC) */
 
+static void of_alias_add(struct alias_prop *ap, struct device_node *np,
+			 int id, const char *stem, int stem_len)
+{
+	ap->id = id;
+	ap->np = np;
+	strncpy(ap->stem, stem, stem_len);
+	ap->stem[stem_len] = 0;
+	list_add_tail(&ap->link, &aliases_lookup);
+	pr_debug("adding DT alias:%s: stem=%s id=%i node=%s\n",
+		 ap->alias, ap->stem, ap->id, np ? np->full_name : NULL);
+}
+
+/**
+ * of_alias_scan() - Scan all properties of 'aliases' node
+ *
+ * The function scans all the properties of 'aliases' node and populate
+ * the global lookup table with the properties.  It returns the
+ * number of alias_prop found, or error code in error case.
+ */
+__init void of_alias_scan(void)
+{
+	struct property *pp;
+
+	if (!of_aliases)
+		return;
+
+	for_each_property(pp, of_aliases->properties) {
+		const char *start = pp->name;
+		const char *end = start + strlen(start);
+		struct device_node *np;
+		struct alias_prop *ap;
+		int id, len;
+
+		/* Skip those we do not want to proceed */
+		if (!strcmp(pp->name, "name") ||
+		    !strcmp(pp->name, "phandle") ||
+		    !strcmp(pp->name, "linux,phandle"))
+			continue;
+
+		np = of_find_node_by_path(pp->value);
+		if (!np)
+			continue;
+
+		/* walk alias backwards to extract the id and 'stem' string */
+		while (isdigit(*(end-1)) && end > start)
+			end--;
+		len = end - start;
+		id = strlen(end) ? simple_strtoul(end, NULL, 10) : -1;
+
+		/* Allocate an alias_prop with enough space for the stem */
+		ap = early_init_dt_alloc_memory_arch(sizeof(*ap) + len + 1, 4);
+		if (!ap)
+			continue;
+		ap->alias = start;
+		of_alias_add(ap, np, id, start, len);
+	}
+}
+
+/**
+ * of_alias_get_id() - Get alias id for the given device_node
+ * @np:		Pointer to the given device_node
+ * @stem:	Alias stem of the given device_node
+ *
+ * The function travels the lookup table to get alias id for the given
+ * device_node and alias stem.  It returns the alias id if find it.
+ * If not, dynamically creates one in the lookup table and returns it,
+ * or returns error code if fail to create.
+ */
+int of_alias_get_id(struct device_node *np, const char *stem)
+{
+	struct alias_prop *app;
+	int id = 0;
+	bool found = false;
+
+	mutex_lock(&of_aliases_mutex);
+	list_for_each_entry(app, &aliases_lookup, link) {
+		if (strcmp(app->stem, stem) != 0)
+			continue;
+
+		if (np == app->np) {
+			found = true;
+			id = app->id;
+			break;
+		}
+
+		if (id <= app->id)
+			id = app->id + 1;
+	}
+
+	/* If an id is not found, then allocate a new one */
+	if (!found) {
+		app = kzalloc(sizeof(*app) + strlen(stem) + 1, 4);
+		if (!app) {
+			id = -ENODEV;
+			goto out;
+		}
+		of_alias_add(app, np, id, stem, strlen(stem));
+	}
+
+ out:
+	mutex_unlock(&of_aliases_mutex);
+
+	return id;
+}
+EXPORT_SYMBOL_GPL(of_alias_get_id);
diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 65200af..13d6d3a 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -707,10 +707,12 @@ void __init unflatten_device_tree(void)
 	__unflatten_device_tree(initial_boot_params, &allnodes,
 				early_init_dt_alloc_memory_arch);
 
-	/* Get pointer to OF "/chosen" node for use everywhere */
+	/* Get pointer to "/chosen" and "/aliasas" nodes for use everywhere */
 	of_chosen = of_find_node_by_path("/chosen");
 	if (of_chosen == NULL)
 		of_chosen = of_find_node_by_path("/chosen@0");
+	of_aliases = of_find_node_by_path("/aliases");
+	of_alias_scan();
 }
 
 #endif /* CONFIG_OF_EARLY_FLATTREE */