binman: Allow 'fill' entry to have a size of 0

The check for this should be for None, not 0. Fix it and add a test.
Signed-off-by: NSimon Glass <sjg@chromium.org>

tools/binman/etype/fill.py

@@ -23,7 +23,7 @@ class Entry_fill(Entry):
     """
     def __init__(self, section, etype, node):
         Entry.__init__(self, section, etype, node)
-        if not self.size:
+        if self.size is None:
             self.Raise("'fill' entry must have a size property")
         self.fill_value = fdt_util.GetByte(self._node, 'fill-byte', 0)
 

tools/binman/ftest.py

@@ -1364,6 +1364,11 @@ class TestFunctional(unittest.TestCase):
         self.assertIn("Node '/binman/u-boot': Please use 'offset' instead of "
                       "'pos'", str(e.exception))
 
+    def testFillZero(self):
+        """Test for an fill entry type with a size of 0"""
+        data = self._DoReadFile('80_fill_empty.dts')
+        self.assertEqual(chr(0) * 16, data)
+
 
 if __name__ == "__main__":
     unittest.main()

tools/binman/test/80_fill_empty.dts

+// SPDX-License-Identifier: GPL-2.0+
+/dts-v1/;
+
+/ {
+	#address-cells = <1>;
+	#size-cells = <1>;
+
+	binman {
+		size = <16>;
+		fill {
+			size = <0>;
+			fill-byte = [ff];
+		};
+	};
+};