[PATCH 2/5] xen: device-tree: add accessors for the addr/size-cells of a node's children.

[Ian Campbell <ian.campbell@citrix.com>]

The existing dt_n_{addr,size}_cells functions tell you which sizes will apply
to this node, which are the #address/size-cells properties of the node's
*parent* (or grandparent, etc).

In some cases we need to know what size applies to a nodes children, which can
include the #address/size-cells properties of the node itself (or its parent).

Refactor the existing function to allow both possibilities.

Clean up the grammar of the existing doc comments a bit.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
---
 xen/common/device_tree.c      |   35 ++++++++++++++++++++++++++----
 xen/include/xen/device_tree.h |   47 ++++++++++++++++++++++++++++++++++-------
 2 files changed, 70 insertions(+), 12 deletions(-)

diff --git a/xen/common/device_tree.c b/xen/common/device_tree.c
index f72b2e9..a4e4eb5 100644
--- a/xen/common/device_tree.c
+++ b/xen/common/device_tree.c
@@ -368,13 +368,17 @@ dt_find_matching_node(struct dt_device_node *from,
     return NULL;
 }
 
-int dt_n_addr_cells(const struct dt_device_node *np)
+/* If parent is true then start from the parent. */
+static int dt_n_addr_cells_common(const struct dt_device_node *np, bool parent)
 {
     const __be32 *ip;
 
     do {
-        if ( np->parent )
+        if ( parent && np->parent )
             np = np->parent;
+        else
+            parent = 1;
+
         ip = dt_get_property(np, "#address-cells", NULL);
         if ( ip )
             return be32_to_cpup(ip);
@@ -383,13 +387,26 @@ int dt_n_addr_cells(const struct dt_device_node *np)
     return DT_ROOT_NODE_ADDR_CELLS_DEFAULT;
 }
 
-int dt_n_size_cells(const struct dt_device_node *np)
+int dt_n_addr_cells(const struct dt_device_node *np)
+{
+    return dt_n_addr_cells_common(np, true);
+}
+
+int dt_n_addr_cells_children(const struct dt_device_node *np)
+{
+    return dt_n_addr_cells_common(np, false);
+}
+
+/* If parent is true then start from the parent. */
+static int dt_n_size_cells_common(const struct dt_device_node *np, bool parent)
 {
     const __be32 *ip;
 
     do {
-        if ( np->parent )
+        if ( parent && np->parent )
             np = np->parent;
+        else
+            parent = 1;
         ip = dt_get_property(np, "#size-cells", NULL);
         if ( ip )
             return be32_to_cpup(ip);
@@ -398,6 +415,16 @@ int dt_n_size_cells(const struct dt_device_node *np)
     return DT_ROOT_NODE_SIZE_CELLS_DEFAULT;
 }
 
+int dt_n_size_cells(const struct dt_device_node *np)
+{
+    return dt_n_size_cells_common(np, true);
+}
+int dt_n_size_cells_children(const struct dt_device_node *np)
+{
+    return dt_n_size_cells_common(np, false);
+}
+
+
 /*
  * Default translator (generic bus)
  */
diff --git a/xen/include/xen/device_tree.h b/xen/include/xen/device_tree.h
index 08db8bc..ac2e876 100644
--- a/xen/include/xen/device_tree.h
+++ b/xen/include/xen/device_tree.h
@@ -513,24 +513,55 @@ int dt_device_get_raw_irq(const struct dt_device_node *device, int index,
 int dt_irq_translate(const struct dt_raw_irq *raw, struct dt_irq *out_irq);
 
 /**
- * dt_n_size_cells - Helper to retrieve the number of cell for the size
- * @np: node to get the value
+ * dt_n_size_cells - Helper to retrieve the number of cells used for
+ * size properties of a node (e.g. the size part of a reg property).
+ *
+ * @np: node to get the value for
  *
- * This function retrieves for a give device-tree node the number of
- * cell for the size field.
+ * This function retrieves for a given device-tree node the number of
+ * cells used for size properties, which is the #size-cells property of
+ * the node's parent (or grandparent etc).
  */
 int dt_n_size_cells(const struct dt_device_node *np);
 
 /**
- * dt_n_addr_cells - Helper to retrieve the number of cell for the address
- * @np: node to get the value
+ * dt_n_size_cells_children - Helper to retrieve the number of cells
+ * used for size properties of child nodes.
+ *
+ * @np: node to get the value for
+ *
+ * This function retrieves the #size-cells field which will apply to
+ * this node's children, which may be specified by this node or its
+ * parent, grantparent etc.
+ */
+int dt_n_size_cells_children(const struct dt_device_node *node);
+
+/**
+ * dt_n_addr_cells - Helper to retrieve the number of cells for
+ * address properties of a node (e.g. the adddress part of a reg
+ * property).
+ *
+ * @np: node to get the value for
  *
- * This function retrieves for a give device-tree node the number of
- * cell for the address field.
+ * This function retrieves for a given device-tree node the number of
+ * cells used for address properties, which is the #address-cells
+ * property of the node's parent (or grantparent, etc).
  */
 int dt_n_addr_cells(const struct dt_device_node *np);
 
 /**
+ * dt_n_size_cells_children - Helper to retrieve the number of cells
+ * used for size properties of child nodes.
+ *
+ * @np: node to get the value for
+ *
+ * This function retrieves the #address-cells field which will apply to
+ * this node's children, which may be specified by this node or its
+ * parent, grantparent etc.
+ */
+int dt_n_addr_cells_children(const struct dt_device_node *np);
+
+/**
  * dt_device_is_available - Check if a device is available for use
  *
  * @device: Node to check for availability
-- 
1.7.10.4