add Python patching script for better maintainability

firmware/patches.txt

@@ -0,0 +1,20 @@
+# Coolscan LS-50
+DF17811 0x170EE "1.02" "2.01"                 # Version in INQUIRY response
+DF17811 0x17106 0x0201 0x0102                 # Version in USB descriptor (High Speed)
+DF17811 0x17118 0x0201 0x0102                 # Version in USB descriptor (Full Speed)
+DF17811 0x2A213 0x03 0x42                     # Enable adapter ID 3
+DF17811 0x2A219 0x05 0x42                     # Enable adapter ID 5
+DF17811 0x2A21F 0x06 0x42                     # Enable adapter ID 6
+DF17811 0x49E49 "1.02" "2.01"                 # Version in strings
+DF17811 0x4A114 0x00400000 0x00000000         # READ BUFFER - allowed RAM start
+DF17811 0x4A118 0x0041FFFF 0x00FFFFFF         # READ BUFFER - allowed RAM end
+
+# Coolscan LS-40
+PT17035 0x169F4 "1.20" "2.01"                 # Version in INQUIRY response
+PT17035 0x16A33 0x2001 0x0102                 # Version in USB descriptor (High Speed)
+PT17035 0x29EB3 0x03 0x42                     # Enable adapter ID 3
+PT17035 0x29EB9 0x05 0x42                     # Enable adapter ID 5
+PT17035 0x29EBF 0x06 0x42                     # Enable adapter ID 6
+PT17035 0x47C3B "1.20" "2.01"                 # Version in strings
+PT17035 0x47F06 0x00400000 0x00000000         # READ BUFFER - allowed RAM start
+PT17035 0x47F0A 0x0041FFFF 0x00FFFFFF         # READ BUFFER - allowed RAM end

scripts/apply_patch.py

@@ -0,0 +1,93 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+#
+# Coolscan firmware patcher. Just a bunch of helper functions really,
+# to make the patches easy to understand and apply.
+
+
+import os
+
+
+class Patch(object):
+
+    def __init__(self, model, offset, length, original, patched):
+
+        self.model = model
+        self.offset = offset
+        self.length = length
+        self.original = original
+        self.patched = patched
+
+    def __repr__(self):
+
+        return "Patch[%s]<0x%x: %s => %s>" % (self.model, self.offset, self.original.hex(), self.patched.hex())
+
+    def apply(self, model, target):
+
+        if model != self.model:
+            return
+        print(self)
+        value = bytes(target[self.offset:self.offset+self.length])
+        assert value == self.original
+        target[self.offset:self.offset+self.length] = self.patched
+
+    @classmethod
+    def parse(cls, line):
+
+        # remove trailing comment
+        line = line.partition('#')[0]
+        # remove whitespace
+        line = line.strip()
+        # bail out if the line was empty
+        if not line:
+            return None
+        # split into components
+        model, offset, original, patched = line.split()
+        # parse/validate them
+        assert offset.startswith("0x")
+        offset = int(offset, 0) - 0x10000 # update files start at 0x10000
+        assert len(original) == len(patched)
+        if original.startswith("0x"):
+            length = len(original)//2 - 1
+            original = int(original, 0).to_bytes(length, byteorder='big')
+            patched = int(patched, 0).to_bytes(length, byteorder='big')
+        elif original.startswith("\""):
+            length = len(original)-2
+            original = original[1:-1].encode('ascii')
+            patched = patched[1:-1].encode('ascii')
+        else:
+            raise ValueError("Unknown format for original/patched")
+        return cls(model, offset, length, original, patched)
+
+
+class Patchset(object):
+
+    def __init__(self, path):
+
+        self.patches = []
+        lines = open(path).readlines()
+        for line in lines:
+            patch = Patch.parse(line)
+            if patch is not None:
+                self.patches.append(patch)
+
+    def apply(self, model, target):
+        for patch in self.patches:
+            patch.apply(model, target)
+
+def main():
+    source_dir = "firmware/original"
+    target_dir = "firmware/patched"
+    files = [ "DF17811.bin", "PT17035.bin" ]
+    patchset = Patchset("firmware/patches.txt")
+
+    for file in files:
+        model = file.removesuffix('.bin')
+        source_path = os.path.join(source_dir, file)
+        target_path = os.path.join(target_dir, file)
+        data = bytearray(open(source_path, 'rb').read())
+        patchset.apply(model, data)
+        open(target_path, 'wb').write(data)
+
+if __name__ == '__main__':
+    main()