fdt: Add function to allow aliases to refer to multiple nodes

Some devices can deal with multiple compatible properties. The devices need to know which nodes to bind to which features. For example an I2C driver which supports two different controller types will want to know which type it is dealing with in each case. The new fdtdec_add_aliases_for_id() function deals with this by allowing the driver to search for additional compatible nodes for a different ID. It can then detect the new ones and perform appropriate processing. Another option considered was to return a tuple (node offset, compat id) and have the function be passed a list of compatible IDs. This is more overhead for the common case though. We may add such a function later if more drivers in U-Boot require it. Signed-off-by: Simon Glass <sjg@chromium.org> Signed-off-by: Tom Warren <twarren@nvidia.com>

fdt: Add function to allow aliases to refer to multiple nodes
Some devices can deal with multiple compatible properties. The devices need to know which nodes to bind to which features. For example an I2C driver which supports two different controller types will want to know which type it is dealing with in each case. The new fdtdec_add_aliases_for_id() function deals with this by allowing the driver to search for additional compatible nodes for a different ID. It can then detect the new ones and perform appropriate processing. Another option considered was to return a tuple (node offset, compat id) and have the function be passed a list of compatible IDs. This is more overhead for the common case though. We may add such a function later if more drivers in U-Boot require it. Signed-off-by: Simon Glass <sjg@chromium.org> Signed-off-by: Tom Warren <twarren@nvidia.com>
Simon Glass · Albert ARIBAUD
1 parent f4589a7d6f
Showing 2 changed files with 41 additions and 4 deletions Side-by-side Diff
include/fdtdec.h
lib/fdtdec.c
@@ -213,6 +213,29 @@
 			enum fdt_compat_id id, int *node_list, int maxcount);
  
 /*
+ * This function is similar to fdtdec_find_aliases_for_id() except that it
+ * adds to the node_list that is passed in. Any 0 elements are considered
+ * available for allocation - others are considered already used and are
+ * skipped.
+ *
+ * You can use this by calling fdtdec_find_aliases_for_id() with an
+ * uninitialised array, then setting the elements that are returned to -1,
+ * say, then calling this function, perhaps with a different compat id.
+ * Any elements you get back that are >0 are new nodes added by the call
+ * to this function.
+ *
+ * Note that if you have some nodes with aliases and some without, you are
+ * sailing close to the wind. The call to fdtdec_find_aliases_for_id() with
+ * one compat_id may fill in positions for which you have aliases defined
+ * for another compat_id. When you later call *this* function with the second
+ * compat_id, the alias positions may already be used. A debug warning may
+ * be generated in this case, but it is safest to define aliases for all
+ * nodes when you care about the ordering.
+ */
+int fdtdec_add_aliases_for_id(const void *blob, const char *name,
+			enum fdt_compat_id id, int *node_list, int maxcount);
+
+/*
  * Get the name for a compatible ID
  *
  * @param id		Compatible ID to look for
@@ -153,10 +153,18 @@
 	return node;
 }
  
-/* TODO: Can we tighten this code up a little? */
 int fdtdec_find_aliases_for_id(const void *blob, const char *name,
 			enum fdt_compat_id id, int *node_list, int maxcount)
 {
+	memset(node_list, '\0', sizeof(*node_list) * maxcount);
+
+	return fdtdec_add_aliases_for_id(blob, name, id, node_list, maxcount);
+}
+
+/* TODO: Can we tighten this code up a little? */
+int fdtdec_add_aliases_for_id(const void *blob, const char *name,
+			enum fdt_compat_id id, int *node_list, int maxcount)
+{
 	int name_len = strlen(name);
 	int nodes[maxcount];
 	int num_found = 0;
@@ -185,8 +193,6 @@
 		       __func__, name);
  
 	/* Now find all the aliases */
-	memset(node_list, '\0', sizeof(*node_list) * maxcount);
-
 	for (offset = fdt_first_property_offset(blob, alias_node);
 			offset > 0;
 			offset = fdt_next_property_offset(blob, offset)) {
  
@@ -233,11 +239,19 @@
 		 * it as done.
 		 */
 		if (fdtdec_get_is_enabled(blob, node)) {
+			if (node_list[number]) {
+				debug("%s: warning: alias '%s' requires that "
+				      "a node be placed in the list in a "
+				      "position which is already filled by "
+				      "node '%s'\n", __func__, path,
+				      fdt_get_name(blob, node, NULL));
+				continue;
+			}
 			node_list[number] = node;
 			if (number >= num_found)
 				num_found = number + 1;
 		}
-		nodes[j] = 0;
+		nodes[found] = 0;
 	}
  
 	/* Add any nodes not mentioned by an alias */
...	...	@@ -213,6 +213,29 @@
213	213	enum fdt_compat_id id, int *node_list, int maxcount);
214	214
215	215	/*
	216	+ * This function is similar to fdtdec_find_aliases_for_id() except that it
	217	+ * adds to the node_list that is passed in. Any 0 elements are considered
	218	+ * available for allocation - others are considered already used and are
	219	+ * skipped.
	220	+ *
	221	+ * You can use this by calling fdtdec_find_aliases_for_id() with an
	222	+ * uninitialised array, then setting the elements that are returned to -1,
	223	+ * say, then calling this function, perhaps with a different compat id.
	224	+ * Any elements you get back that are >0 are new nodes added by the call
	225	+ * to this function.
	226	+ *
	227	+ * Note that if you have some nodes with aliases and some without, you are
	228	+ * sailing close to the wind. The call to fdtdec_find_aliases_for_id() with
	229	+ * one compat_id may fill in positions for which you have aliases defined
	230	+ * for another compat_id. When you later call this function with the second
	231	+ * compat_id, the alias positions may already be used. A debug warning may
	232	+ * be generated in this case, but it is safest to define aliases for all
	233	+ * nodes when you care about the ordering.
	234	+ */
	235	+int fdtdec_add_aliases_for_id(const void blob, const char name,
	236	+ enum fdt_compat_id id, int *node_list, int maxcount);
	237	+
	238	+/*
216	239	* Get the name for a compatible ID
217	240	*
218	241	* @param id Compatible ID to look for
...	...	@@ -153,10 +153,18 @@
153	153	return node;
154	154	}
155	155
156		-/* TODO: Can we tighten this code up a little? */
157	156	int fdtdec_find_aliases_for_id(const void blob, const char name,
158	157	enum fdt_compat_id id, int *node_list, int maxcount)
159	158	{
	159	+ memset(node_list, '\0', sizeof(node_list) maxcount);
	160	+
	161	+ return fdtdec_add_aliases_for_id(blob, name, id, node_list, maxcount);
	162	+}
	163	+
	164	+/* TODO: Can we tighten this code up a little? */
	165	+int fdtdec_add_aliases_for_id(const void blob, const char name,
	166	+ enum fdt_compat_id id, int *node_list, int maxcount)
	167	+{
160	168	int name_len = strlen(name);
161	169	int nodes[maxcount];
162	170	int num_found = 0;
...	...	@@ -185,8 +193,6 @@
185	193	__func__, name);
186	194
187	195	/* Now find all the aliases */
188		- memset(node_list, '\0', sizeof(node_list) maxcount);
189		-
190	196	for (offset = fdt_first_property_offset(blob, alias_node);
191	197	offset > 0;
192	198	offset = fdt_next_property_offset(blob, offset)) {
193	199
...	...	@@ -233,11 +239,19 @@
233	239	* it as done.
234	240	*/
235	241	if (fdtdec_get_is_enabled(blob, node)) {
	242	+ if (node_list[number]) {
	243	+ debug("%s: warning: alias '%s' requires that "
	244	+ "a node be placed in the list in a "
	245	+ "position which is already filled by "
	246	+ "node '%s'\n", __func__, path,
	247	+ fdt_get_name(blob, node, NULL));
	248	+ continue;
	249	+ }
236	250	node_list[number] = node;
237	251	if (number >= num_found)
238	252	num_found = number + 1;
239	253	}
240		- nodes[j] = 0;
	254	+ nodes[found] = 0;
241	255	}
242	256
243	257	/* Add any nodes not mentioned by an alias */