dm: core: Add definitions for multiple ofnode trees

At present, unless OF_LIVE is enabled, ofnode only supports access to one
device tree, the control FDT. This is because only the node offset is
encoded in ofnode, with the tree being implicit.

This makes ofnode (without OF_LIVE) unsuitable for device tree fixups, as
implemented by ft_board_setup() and other such functions.

To solve this, we can use the top bits of the node offset to hold a tree
ID.

Add the definitions for this.

Signed-off-by: Simon Glass <sjg@chromium.org>

1 files changed, 31 insertions, 2 deletions

diff --git a/include/dm/ofnode_decl.h b/include/dm/ofnode_decl.h
index f666a0287b..5c2115aab0 100644
--- a/include/dm/ofnode_decl.h
+++ b/include/dm/ofnode_decl.h
@@ -31,8 +31,18 @@
  * this increases code size slightly due to the subtraction. Since it offers no
  * real benefit, the approach described here seems best.
  *
- * For now these points use constant types, since we don't allow writing
- * the DT.
+ * Where multiple trees are in use, this works without any trouble with live
+ * tree, except for aliases, such as ofnode_path("mmc0"), which only work on the
+ * control FDT. When the flat tree is in use, the trees are registered and a
+ * 'tree ID' is encoded into the top bits of @of_offset - see immediately below
+ * for the associated macro definitions. Note that 64-bit machines use the same
+ * encoding, even though there is more space available. This is partly because
+ * the FDT format contains 32-bit values for things like the string-table
+ * offset, therefore 64-bit offsets cannot be supported anyway.
+ *
+ * For the multiple-tree case, an invalid offset (i.e. with of_offset < 0) is
+ * still invalid. It does not contain a tree ID. So there is no way of knowing
+ * which tree produced the invalid offset.
  *
  * @np: Pointer to device node, used for live tree
  * @of_offset: Pointer into flat device tree, used for flat tree. Note that this
@@ -43,6 +53,25 @@ typedef union ofnode_union {
 	long of_offset;
 } ofnode;
 
+/* shift for the tree ID within of_offset */
+#define OF_TREE_SHIFT 28
+
+/* mask to obtain the device tree offset from of_offset */
+#define OF_TREE_MASK ((1 << OF_TREE_SHIFT) - 1)
+
+/* encode a tree ID and node offset into an of_offset value */
+#define OFTREE_NODE(tree_id, offs)	((tree_id) << OF_TREE_SHIFT | (offs))
+
+/* decode the node offset from an of_offset value */
+#define OFTREE_OFFSET(of_offs)		((of_offs) & OF_TREE_MASK)
+
+/* decode the tree ID from an of_offset value */
+#define OFTREE_TREE_ID(of_offs)		((of_offs) >> OF_TREE_SHIFT)
+
+/* encode a node offset in the tree given by another node's of_offset value */
+#define OFTREE_MAKE_NODE(other_of_offset, offs)	\
+		(((offs) & OF_TREE_MASK) | ((other_of_offset) & ~OF_TREE_MASK))
+
 /**
  * struct ofprop - reference to a property of a device tree node
  *