[PATCH v2 1/5] dt: add of_alias_scan and of_alias_get_id

[Shawn Guo <shawn.guo-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>]

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-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
Cc: Grant Likely <grant.likely-s3s/WqlpOiPyB63q8FvJNQ@public.gmane.org>
---
 drivers/of/base.c  |  181 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 drivers/of/fdt.c   |    6 ++
 include/linux/of.h |    7 ++
 3 files changed, 194 insertions(+), 0 deletions(-)

diff --git a/drivers/of/base.c b/drivers/of/base.c
index 632ebae..89efd10 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -17,14 +17,38 @@
  *      as published by the Free Software Foundation; either version
  *      2 of the License, or (at your option) any later version.
  */
+#include <linux/bootmem.h>
+#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
+ * @alias_id:	Alias id decoded from alias
+ * @alias_stem:	Alias stem name decoded from alias
+ *
+ * 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 alias_id;
+	char alias_stem[0];
+};
+
+static LIST_HEAD(aliases_lookup);
+
 struct device_node *allnodes;
 struct device_node *of_chosen;
+struct device_node *of_aliases;
 
 /* use when traversing tree through the allnext, child, sibling,
  * or parent members of struct device_node.
@@ -922,3 +946,160 @@ out_unlock:
 }
 #endif /* defined(CONFIG_OF_DYNAMIC) */
 
+/*
+ * of_alias_find_available_id - Find an available 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 find an available id for the
+ * given device_node with given alias stem.  It returns the id found.
+ */
+static int of_alias_find_available_id(struct device_node *np, const char *stem)
+{
+	struct alias_prop *app;
+	int id = 0;
+
+	while (1) {
+		bool used = false;
+		list_for_each_entry(app, &aliases_lookup, link) {
+			if (!strcmp(app->alias_stem, stem) &&
+			    app->alias_id == id) {
+				used = true;
+				break;
+			}
+		}
+
+		if (used)
+			id++;
+		else
+			return id;
+	}
+}
+
+/**
+ * of_alias_lookup_add - Add alias into lookup table
+ * @alias:	Alias name
+ * @id:		Alias id
+ * @stem:	Alias stem name
+ * @np:		Pointer to device_node
+ *
+ * The function adds one alias into the lookup table and populate it
+ * with the info passed in.  It returns 0 in sucess, or error code.
+ */
+static int of_alias_lookup_add(char *alias, int id, const char *stem,
+			       struct device_node *np)
+{
+	struct alias_prop *app;
+	size_t sz = sizeof(*app) + strlen(stem) + 1;
+
+	app = kzalloc(sz, GFP_KERNEL);
+	if (!app) {
+		/*
+		 * It may fail due to being called by boot code,
+		 * so try alloc_bootmem before return error.
+		 */
+		app = alloc_bootmem(sz);
+		if (!app)
+			return -ENOMEM;
+	}
+
+	app->np = np;
+	app->alias = alias;
+	app->alias_id = id;
+	strcpy(app->alias_stem, stem);
+	list_add_tail(&app->link, &aliases_lookup);
+
+	return 0;
+}
+
+/**
+ * of_alias_decode - Decode alias stem and id from alias name
+ * @alias:	Alias name to be decoded
+ * @stem:	Pointer used to return stem name
+ *
+ * The function decodes alias stem name and alias id from the given
+ * alias name.  It returns stem name via parameter 'stem', and stem id
+ * via the return value.  If no id is found in alias name, it returns 0
+ * as the default.
+ */
+static int of_alias_decode(char *alias, char *stem)
+{
+	int len = strlen(alias);
+	char *end = alias + len;
+
+	while (isdigit(*--end))
+		len--;
+
+	strncpy(stem, alias, len);
+	stem[len] = '\0';
+
+	return strlen(++end) ? simple_strtoul(end, NULL, 10) : 0;
+}
+
+/**
+ * of_alias_scan - Scan all properties of 'aliases' node
+ *
+ * The function scans all the properties of 'aliases' node and populate
+ * the the global lookup table with the properties.  It returns the
+ * number of alias_prop found, or error code in error case.
+ */
+int of_alias_scan(void)
+{
+	struct property *pp;
+	int ret, num = 0;
+
+	if (!of_aliases)
+		return -ENODEV;
+
+	for_each_property(pp, of_aliases->properties) {
+		char stem[32];
+		int id = of_alias_decode(pp->name, stem);
+
+		/* Skip those we do not want to proceed */
+		if (!strcmp(pp->name, "name") ||
+		    !strcmp(pp->name, "phandle") ||
+		    !strcmp(pp->name, "linux,phandle"))
+			continue;
+
+		ret = of_alias_lookup_add(pp->name, id, stem,
+					  of_find_node_by_path(pp->value));
+		if (ret < 0)
+			return ret;
+		else
+			num++;
+	}
+
+	return num;
+}
+
+/**
+ * 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 = -1;
+
+	list_for_each_entry(app, &aliases_lookup, link) {
+		if (np == app->np) {
+			id = app->alias_id;
+			break;
+		}
+	}
+
+	if (id == -1) {
+		id = of_alias_find_available_id(np, stem);
+		if (of_alias_lookup_add(NULL, id, stem, np) < 0)
+			return -ENODEV;
+	}
+
+	return id;
+}
+EXPORT_SYMBOL_GPL(of_alias_get_id);
diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 65200af..998dc63 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -711,6 +711,12 @@ void __init unflatten_device_tree(void)
 	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");
+	if (of_aliases == NULL)
+		of_aliases = of_find_node_by_path("/aliases@0");
+
+	of_alias_scan();
 }
 
 #endif /* CONFIG_OF_EARLY_FLATTREE */
diff --git a/include/linux/of.h b/include/linux/of.h
index bfc0ed1..c35cc47 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -68,6 +68,7 @@ struct device_node {
 /* Pointer for first entry in chain of all nodes. */
 extern struct device_node *allnodes;
 extern struct device_node *of_chosen;
+extern struct device_node *of_aliases;
 extern rwlock_t devtree_lock;
 
 static inline bool of_have_populated_dt(void)
@@ -201,6 +202,9 @@ extern int of_device_is_available(const struct device_node *device);
 extern const void *of_get_property(const struct device_node *node,
 				const char *name,
 				int *lenp);
+#define for_each_property(pp, properties) \
+	for (pp = properties; pp != NULL; pp = pp->next)
+
 extern int of_n_addr_cells(struct device_node *np);
 extern int of_n_size_cells(struct device_node *np);
 extern const struct of_device_id *of_match_node(
@@ -213,6 +217,9 @@ extern int of_parse_phandles_with_args(struct device_node *np,
 	const char *list_name, const char *cells_name, int index,
 	struct device_node **out_node, const void **out_args);
 
+extern int of_alias_scan(void);
+extern int of_alias_get_id(struct device_node *np, const char *stem);
+
 extern int of_machine_is_compatible(const char *compat);
 
 extern int prom_add_property(struct device_node* np, struct property* prop);
-- 
1.7.4.1