diff --git a/bootloader.h b/bootloader.h
index 2e749aa..3d4302f 100644
--- a/bootloader.h
+++ b/bootloader.h
@@ -47,4 +47,13 @@
 int get_bootloader_message(struct bootloader_message *out);
 int set_bootloader_message(const struct bootloader_message *in);
 
+/* Write an update to the cache partition for update-radio or update-hboot.
+ * Note, this destroys any filesystem on the cache partition!
+ * The expected bitmap format is 240x320, 16bpp (2Bpp), RGB 5:6:5.
+ */
+int write_update_for_bootloader(
+        const char *update, int update_len,
+        int bitmap_width, int bitmap_height, int bitmap_bpp,
+        const char *busy_bitmap, const char *error_bitmap);
+
 #endif