pylibfdt: Add address_cells() and size_cells()

Finding out how many cells a node's children use for addresses and sizes
currently requires calling the raw fdt_address_cells()/fdt_size_cells()
wrappers with the private FdtRo._fdt buffer, as the class exposes no
methods for them.

Add them to FdtRo alongside the other node accessors, and test them.

Signed-off-by: Alexey Charkov <alchark@flipper.net>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

pylibfdt/libfdt.i

@@ -302,6 +302,38 @@ class FdtRo(object):
         check_err(val[0], quiet)
         return val[1:]
 
+    def address_cells(self, nodeoffset, quiet=()):
+        """Return the number of address cells used by a node's children
+
+        Args:
+            nodeoffset: Offset of the node to check
+            quiet: Errors to ignore (empty to raise on all errors)
+
+        Returns:
+            Number of address cells used by the children of @nodeoffset
+
+        Raises:
+            FdtException if the node has an invalid #address-cells property,
+            or another error occurs
+        """
+        return check_err(fdt_address_cells(self._fdt, nodeoffset), quiet)
+
+    def size_cells(self, nodeoffset, quiet=()):
+        """Return the number of size cells used by a node's children
+
+        Args:
+            nodeoffset: Offset of the node to check
+            quiet: Errors to ignore (empty to raise on all errors)
+
+        Returns:
+            Number of size cells used by the children of @nodeoffset
+
+        Raises:
+            FdtException if the node has an invalid #size-cells property, or
+            another error occurs
+        """
+        return check_err(fdt_size_cells(self._fdt, nodeoffset), quiet)
+
     def subnode_offset(self, parentoffset, name, quiet=()):
         """Get the offset of a named subnode
 

tests/pylibfdt_tests.py

@@ -411,6 +411,21 @@ class PyLibfdtBasicTests(unittest.TestCase):
                           self.fdt.get_mem_rsv(0))
         self.assertEqual([123456789, 0o10000], self.fdt.get_mem_rsv(1))
 
+    def testCells(self):
+        """Test that we can read #address-cells and #size-cells"""
+        self.assertEqual(1, self.fdt.address_cells(0))
+        self.assertEqual(0, self.fdt.size_cells(0))
+
+        # A node without the properties inherits neither, so the libfdt
+        # defaults of 2 and 1 apply
+        node = self.fdt.path_offset('/subnode@1')
+        self.assertEqual(2, self.fdt.address_cells(node))
+        self.assertEqual(1, self.fdt.size_cells(node))
+
+        node = self.fdt.path_offset('/subnode@2')
+        self.assertEqual(1, self.fdt.address_cells(node))
+        self.assertEqual(0, self.fdt.size_cells(node))
+
     def testEmpty(self):
         """Test that we can create an empty tree"""
         self.assertEqual(-libfdt.NOSPACE,