pylibfdt: Allow reading integer values from properties

Extend the Properties class with some functions to read a single integer
property. Add a new getprop_obj() function to return a Property object
instead of the raw data.

This suggested approach can be extended to handle other types, as well as
arrays.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

pylibfdt/libfdt.i

@@ -488,7 +488,9 @@ class Fdt:
             quiet: Errors to ignore (empty to raise on all errors)
 
         Returns:
-            Value of property as a string of bytes, or -ve error number
+            Value of property as a Property object (which can be used as a
+               bytearray/string), or -ve error number. On failure, returns an
+               integer error
 
         Raises:
             FdtError if any error occurs (e.g. the property is not found)
@@ -497,8 +499,7 @@ class Fdt:
                                quiet)
         if isinstance(pdata, (int)):
             return pdata
-        # Use bytes() rather than string(). This works on both Python 2 and 3
-        return bytes(pdata[0])
+        return Property(prop_name, bytearray(pdata[0]))
 
     def get_phandle(self, nodeoffset):
         """Get the phandle of a node
@@ -623,6 +624,21 @@ class Property(bytearray):
     def __init__(self, name, value):
         bytearray.__init__(self, value)
         self.name = name
+
+    def as_cell(self, fmt):
+        return struct.unpack('>' + fmt, self)[0]
+
+    def as_uint32(self):
+        return self.as_cell('L')
+
+    def as_int32(self):
+        return self.as_cell('l')
+
+    def as_uint64(self):
+        return self.as_cell('Q')
+
+    def as_int64(self):
+        return self.as_cell('q')
 %}
 
 %rename(fdt_property) fdt_property_func;

tests/pylibfdt_tests.py

@@ -102,6 +102,7 @@ class PyLibfdtTests(unittest.TestCase):
     def setUp(self):
         """Read in the device tree we use for testing"""
         self.fdt = _ReadFdt('test_tree1.dtb')
+        self.fdt2 = _ReadFdt('test_props.dtb')
 
     def GetPropList(self, node_path):
         """Read a list of properties from a node
@@ -368,6 +369,17 @@ class PyLibfdtTests(unittest.TestCase):
         node2 = self.fdt.path_offset('/subnode@2/subsubnode@0')
         self.assertEquals(node2, self.fdt.node_offset_by_phandle(0x2001))
 
+    def get_prop(self, name):
+        return self.fdt2.getprop(0, name)
+
+    def testGetIntProperties(self):
+        """Test that we can access properties as integers"""
+        self.assertEquals(0xdeadbeef, self.get_prop("prop-hex32").as_uint32())
+        self.assertEquals(123, self.get_prop("prop-uint32").as_uint32())
+        self.assertEquals(-2, self.get_prop("prop-int32").as_int32())
+        self.assertEquals(9223372036854775807,
+                          self.get_prop("prop-uint64").as_uint64())
+        self.assertEquals(-2, self.get_prop("prop-int64").as_int64())
 
     def testReserveMap(self):
         """Test that we can access the memory reserve map"""

tests/run_tests.sh

@@ -888,6 +888,7 @@ fdtoverlay_tests() {
 }
 
 pylibfdt_tests () {
+    run_dtc_test -I dts -O dtb -o test_props.dtb test_props.dts
     TMP=/tmp/tests.stderr.$$
     python pylibfdt_tests.py -v 2> $TMP
 

tests/test_props.dts

@@ -0,0 +1,11 @@
+/dts-v1/;
+
+/ {
+	compatible = "test_props";
+	prop-hex32 = <0xdeadbeef>;
+	prop-uint32 = <123>;
+	prop-int32 = <0xfffffffe>;
+	prop-hex64 = /bits/ 64 <0xdeadbeef01abcdef>;
+	prop-uint64 = /bits/ 64 <9223372036854775807>;
+	prop-int64 = /bits/ 64 <0xfffffffffffffffe>;
+};