binman: Move CompressData() into Entry base class

At present this is only used by blobs. To allow it to be used by other
entry types (such as sections), move it into the base class.

Also read the compression type in the base class.

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

tools/binman/entry.py

@@ -180,6 +180,9 @@ class Entry(object):
         self.expand_size = fdt_util.GetBool(self._node, 'expand-size')
         self.missing_msg = fdt_util.GetString(self._node, 'missing-msg')
 
+        # This is only supported by blobs and sections at present
+        self.compress = fdt_util.GetString(self._node, 'compress', 'none')
+
     def GetDefaultFilename(self):
         return None
 
@@ -836,3 +839,17 @@ features to produce new behaviours.
             list of possible tags, most desirable first
         """
         return list(filter(None, [self.missing_msg, self.name, self.etype]))
+
+    def CompressData(self, indata):
+        """Compress data according to the entry's compression method
+
+        Args:
+            indata: Data to compress
+
+        Returns:
+            Compressed data (first word is the compressed size)
+        """
+        if self.compress != 'none':
+            self.uncomp_size = len(indata)
+        data = tools.Compress(indata, self.compress)
+        return data

tools/binman/etype/blob.py

@@ -33,7 +33,6 @@ class Entry_blob(Entry):
     def __init__(self, section, etype, node):
         super().__init__(section, etype, node)
         self._filename = fdt_util.GetString(self._node, 'filename', self.etype)
-        self.compress = fdt_util.GetString(self._node, 'compress', 'none')
 
     def ObtainContents(self):
         self._filename = self.GetDefaultFilename()
@@ -48,12 +47,6 @@ class Entry_blob(Entry):
         self.ReadBlobContents()
         return True
 
-    def CompressData(self, indata):
-        if self.compress != 'none':
-            self.uncomp_size = len(indata)
-        data = tools.Compress(indata, self.compress)
-        return data
-
     def ReadBlobContents(self):
         """Read blob contents into memory