From 3fb56f8b9b3add0a4e526387d1b332971b0495cb Mon Sep 17 00:00:00 2001
From: James Aguilar <aguilar.james@gmail.com>
Date: Tue, 23 Dec 2025 23:27:13 +0000
Subject: [PATCH] firmware: Don't add checksums when not needed.

This fixes an issue where the EV3 firmware had checksums appended to
it that made its size not align to the sector size, causing flashing
to fail.
---
 src/firmware/sagas.ts | 42 ++++++++++++++++++++++--------------------
 1 file changed, 22 insertions(+), 20 deletions(-)

diff --git a/src/firmware/sagas.ts b/src/firmware/sagas.ts
index a25e5b26..7ac4fea7 100644
--- a/src/firmware/sagas.ts
+++ b/src/firmware/sagas.ts
@@ -351,32 +351,20 @@ function* loadFirmware(
         'Expected metadata to be v2.x',
     );
 
-    const firmware = new Uint8Array(firmwareBase.length + 4);
-    const firmwareView = new DataView(firmware.buffer);
-
-    firmware.set(firmwareBase);
-
-    // empty string means use default name (don't write over firmware)
-    if (hubName) {
-        firmware.set(encodeHubName(hubName, metadata), metadata['hub-name-offset']);
-    }
-
-    const checksum = (function () {
+    const [checksumFunc, checksumExtraLength] = (() => {
         switch (metadata['checksum-type']) {
             case 'sum':
-                return sumComplement32(
-                    firmwareIterator(firmwareView, metadata['checksum-size']),
-                );
+                return [sumComplement32, 4];
             case 'crc32':
-                return crc32(firmwareIterator(firmwareView, metadata['checksum-size']));
+                return [crc32, 4];
             case 'none':
-                return null;
+                return [null, 0];
             default:
-                return undefined;
+                return [undefined, 0];
         }
     })();
 
-    if (checksum === undefined) {
+    if (checksumFunc === undefined) {
         // FIXME: we should return error/throw instead
         yield* put(
             didFailToFinish(
@@ -391,8 +379,22 @@ function* loadFirmware(
         throw new Error('unreachable');
     }
 
-    if (checksum !== null) {
-        firmwareView.setUint32(firmwareBase.length, checksum, true);
+    const firmware = new Uint8Array(firmwareBase.length + checksumExtraLength);
+    const firmwareView = new DataView(firmware.buffer);
+
+    firmware.set(firmwareBase);
+
+    // empty string means use default name (don't write over firmware)
+    if (hubName) {
+        firmware.set(encodeHubName(hubName, metadata), metadata['hub-name-offset']);
+    }
+
+    if (checksumFunc !== null) {
+        firmwareView.setUint32(
+            firmwareBase.length,
+            checksumFunc(firmwareIterator(firmwareView, metadata['checksum-size'])),
+            true,
+        );
     }
 
     return { firmware, deviceId: metadata['device-id'] };