drivers: of: add function to scan fdt nodes given by path

Add a function to scan the flattened device-tree starting from the
node given by the path. It is used to extract information (like reserved
memory), which is required on early boot before we can unflatten the tree.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Acked-by: Tomasz Figa <t.figa@samsung.com>
Reviewed-by: Rob Herring <rob.herring@calxeda.com>

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 6bb7cf2de556b559d1f54f9d1c7c3ff297138a3a..585b1a67cfbe6e42ffa83f2a1b3afa3110c3bf4f 100644 (file)
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -543,6 +543,82 @@ int __init of_flat_dt_match(unsigned long node, const char *const *compat)
        return of_fdt_match(initial_boot_params, node, compat);
 }
 
+struct fdt_scan_status {
+       const char *name;
+       int namelen;
+       int depth;
+       int found;
+       int (*iterator)(unsigned long node, const char *uname, int depth, void *data);
+       void *data;
+};
+
+/**
+ * fdt_scan_node_by_path - iterator for of_scan_flat_dt_by_path function
+ */
+static int __init fdt_scan_node_by_path(unsigned long node, const char *uname,
+                                       int depth, void *data)
+{
+       struct fdt_scan_status *st = data;
+
+       /*
+        * if scan at the requested fdt node has been completed,
+        * return -ENXIO to abort further scanning
+        */
+       if (depth <= st->depth)
+               return -ENXIO;
+
+       /* requested fdt node has been found, so call iterator function */
+       if (st->found)
+               return st->iterator(node, uname, depth, st->data);
+
+       /* check if scanning automata is entering next level of fdt nodes */
+       if (depth == st->depth + 1 &&
+           strncmp(st->name, uname, st->namelen) == 0 &&
+           uname[st->namelen] == 0) {
+               st->depth += 1;
+               if (st->name[st->namelen] == 0) {
+                       st->found = 1;
+               } else {
+                       const char *next = st->name + st->namelen + 1;
+                       st->name = next;
+                       st->namelen = strcspn(next, "/");
+               }
+               return 0;
+       }
+
+       /* scan next fdt node */
+       return 0;
+}
+
+/**
+ * of_scan_flat_dt_by_path - scan flattened tree blob and call callback on each
+ *                          child of the given path.
+ * @path: path to start searching for children
+ * @it: callback function
+ * @data: context data pointer
+ *
+ * This function is used to scan the flattened device-tree starting from the
+ * node given by path. It is used to extract information (like reserved
+ * memory), which is required on ealy boot before we can unflatten the tree.
+ */
+int __init of_scan_flat_dt_by_path(const char *path,
+       int (*it)(unsigned long node, const char *name, int depth, void *data),
+       void *data)
+{
+       struct fdt_scan_status st = {path, 0, -1, 0, it, data};
+       int ret = 0;
+
+       if (initial_boot_params)
+                ret = of_scan_flat_dt(fdt_scan_node_by_path, &st);
+
+       if (!st.found)
+               return -ENOENT;
+       else if (ret == -ENXIO) /* scan has been completed */
+               return 0;
+       else
+               return ret;
+}
+
 #ifdef CONFIG_BLK_DEV_INITRD
 /**
  * early_init_dt_check_for_initrd - Decode initrd location from flat tree

diff --git a/include/linux/of_fdt.h b/include/linux/of_fdt.h
index ed136ad698ce622e4d150d7fda337a99c78d5a4e..19f26f8d2202bd5dc42100458945150c9bd46d31 100644 (file)
--- a/include/linux/of_fdt.h
+++ b/include/linux/of_fdt.h
@@ -90,6 +90,9 @@ extern void *of_get_flat_dt_prop(unsigned long node, const char *name,
 extern int of_flat_dt_is_compatible(unsigned long node, const char *name);
 extern int of_flat_dt_match(unsigned long node, const char *const *matches);
 extern unsigned long of_get_flat_dt_root(void);
+extern int of_scan_flat_dt_by_path(const char *path,
+       int (*it)(unsigned long node, const char *name, int depth, void *data),
+       void *data);
 
 extern int early_init_dt_scan_chosen(unsigned long node, const char *uname,
                                     int depth, void *data);