libfdt: Add function to explicitly expand aliases

Kumar has already added alias expansion to fdt_path_offset().
However, in some circumstances it may be convenient for the user of
libfdt to explicitly get the string expansion of an alias.  This patch
adds a function to do this, fdt_get_alias(), and uses it to implement
fdt_path_offset().

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

diff --git a/include/libfdt.h b/include/libfdt.h
index 5492a535207816765730f366bbec52e600969e40..7cad68c3cefc648676adf9c8c7bb1b37c2d4e54b 100644 (file)
--- a/include/libfdt.h
+++ b/include/libfdt.h
@@ -458,6 +458,32 @@ static inline void *fdt_getprop_w(void *fdt, int nodeoffset,
  */
 uint32_t fdt_get_phandle(const void *fdt, int nodeoffset);
 
+/**
+ * fdt_get_namelen - get alias based on substring
+ * @fdt: pointer to the device tree blob
+ * @name: name of the alias th look up
+ * @namelen: number of characters of name to consider
+ *
+ * Identical to fdt_get_alias(), but only examine the first namelen
+ * characters of name for matching the alias name.
+ */
+const char *fdt_get_alias_namelen(const void *fdt,
+                                 const char *name, int namelen);
+
+/**
+ * fdt_get_alias - retreive the path referenced by a given alias
+ * @fdt: pointer to the device tree blob
+ * @name: name of the alias th look up
+ *
+ * fdt_get_alias() retrieves the value of a given alias.  That is, the
+ * value of the property named 'name' in the node /aliases.
+ *
+ * returns:
+ *     a pointer to the expansion of the alias named 'name', of it exists
+ *     NULL, if the given alias or the /aliases node does not exist
+ */
+const char *fdt_get_alias(const void *fdt, const char *name);
+
 /**
  * fdt_get_path - determine the full path of a node
  * @fdt: pointer to the device tree blob

diff --git a/libfdt/fdt_ro.c b/libfdt/fdt_ro.c
index f559eeda06a9b600dfb7281e2f22c784e3b8fb95..b705f91ecb760cd8120589f23865d58363ff56f0 100644 (file)
--- a/libfdt/fdt_ro.c
+++ b/libfdt/fdt_ro.c
@@ -145,17 +145,12 @@ int fdt_path_offset(const void *fdt, const char *path)
 
        /* see if we have an alias */
        if (*path != '/') {
-               const char *q;
-               int aliasoffset = fdt_path_offset(fdt, "/aliases");
-
-               if (aliasoffset < 0)
-                       return -FDT_ERR_BADPATH;
+               const char *q = strchr(path, '/');
 
-               q = strchr(path, '/');
                if (!q)
                        q = end;
 
-               p = fdt_getprop_namelen(fdt, aliasoffset, path, q - p, NULL);
+               p = fdt_get_alias_namelen(fdt, p, q - p);
                if (!p)
                        return -FDT_ERR_BADPATH;
                offset = fdt_path_offset(fdt, p);
@@ -306,6 +301,23 @@ uint32_t fdt_get_phandle(const void *fdt, int nodeoffset)
        return fdt32_to_cpu(*php);
 }
 
+const char *fdt_get_alias_namelen(const void *fdt,
+                                 const char *name, int namelen)
+{
+       int aliasoffset;
+
+       aliasoffset = fdt_path_offset(fdt, "/aliases");
+       if (aliasoffset < 0)
+               return NULL;
+
+       return fdt_getprop_namelen(fdt, aliasoffset, name, namelen, NULL);
+}
+
+const char *fdt_get_alias(const void *fdt, const char *name)
+{
+       return fdt_get_alias_namelen(fdt, name, strlen(name));
+}
+
 int fdt_get_path(const void *fdt, int nodeoffset, char *buf, int buflen)
 {
        int pdepth = 0, p = 0;