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.

v3: Split out automatic addition of aliases on id lookup so that it can be
    debated separately from the core functionality.
v2: - Add of_chosen/of_aliases populating and of_alias_scan() invocation
    for OF_PROMTREE.
    - Add locking
    - rework parse loop

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

3 files changed, 131 insertions, 4 deletions

diff --git a/drivers/of/base.c b/drivers/of/base.c
index 3ff22e32b602..8abde58cbe82 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 +1013,99 @@ 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->np = np;
+        ap->id = id;
+        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 the global lookup table with the properties.  It returns the
+ * number of alias_prop found, or error code in error case.
+ *
+ * @dt_alloc:   An allocator that provides a virtual address to memory
+ *              for the resulting tree
+ */
+void of_alias_scan(void * (*dt_alloc)(u64 size, u64 align))
+{
+        struct property *pp;
+
+        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)
+                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 the alias backwards to extract the id and work out
+                 * the 'stem' string */
+                while (isdigit(*(end-1)) && end > start)
+                        end--;
+                len = end - start;
+
+                if (kstrtoint(end, 10, &id) < 0)
+                        continue;
+
+                /* Allocate an alias_prop with enough space for the stem */
+                ap = dt_alloc(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.
+ */
+int of_alias_get_id(struct device_node *np, const char *stem)
+{
+        struct alias_prop *app;
+        int id = -ENODEV;
+
+        mutex_lock(&of_aliases_mutex);
+        list_for_each_entry(app, &aliases_lookup, link) {
+                if (strcmp(app->stem, stem) != 0)
+                        continue;
+
+                if (np == app->np) {
+                        id = app->id;
+                        break;
+                }
+        }
+        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 65200af29c52..aeec35bc3789 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -707,10 +707,8 @@ 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 */
-        of_chosen = of_find_node_by_path("/chosen");
-        if (of_chosen == NULL)
-                of_chosen = of_find_node_by_path("/chosen@0");
+        /* Get pointer to "/chosen" and "/aliasas" nodes for use everywhere */
+        of_alias_scan(early_init_dt_alloc_memory_arch);
 }
 
 #endif /* CONFIG_OF_EARLY_FLATTREE */
diff --git a/drivers/of/pdt.c b/drivers/of/pdt.c
index 4d87b5dc9284..bc5b3990f6ed 100644
--- a/drivers/of/pdt.c
+++ b/drivers/of/pdt.c
@@ -229,6 +229,11 @@ static struct device_node * __init of_pdt_build_tree(struct device_node *parent,
         return ret;
 }
 
+static void *kernel_tree_alloc(u64 size, u64 align)
+{
+        return prom_early_alloc(size);
+}
+
 void __init of_pdt_build_devicetree(phandle root_node, struct of_pdt_ops *ops)
 {
         struct device_node **nextp;
@@ -245,4 +250,7 @@ void __init of_pdt_build_devicetree(phandle root_node, struct of_pdt_ops *ops)
         nextp = &allnodes->allnext;
         allnodes->child = of_pdt_build_tree(allnodes,
                         of_pdt_prom_ops->getchild(allnodes->phandle), &nextp);
+
+        /* Get pointer to "/chosen" and "/aliasas" nodes for use everywhere */
+        of_alias_scan(kernel_tree_alloc);
 }