Factor out read_firmware_device()

include/chromeos/firmware_storage.h

Index: include/chromeos/firmware_storage.h
diff --git a/include/chromeos/firmware_storage.h b/include/chromeos/firmware_storage.h
index 672b39534a70b60db4e7d727753317d8d153dcee..3349b1be6d7419c64ec98f9dc75e96083f1a1ccf 100644
--- a/include/chromeos/firmware_storage.h
+++ b/include/chromeos/firmware_storage.h
@@ -72,4 +72,13 @@ void GetFirmwareBody_setup(firmware_storage_t *f,
 /* Dispose fields that are used for communicating with GetFirmwareBody(). */
 void GetFirmwareBody_dispose(firmware_storage_t *f);
 
+/*
+ * Read <count> bytes, starting from <offset>, from firmware storage
+ * device <file> into buffer <buf>.
+ *
+ * Return 0 on success, non-zero on error.
+ */
+int read_firmware_device(firmware_storage_t *file, off_t offset, void *buf,
+		size_t count);
+
 #endif /* __FIRMWARE_STORAGE_H_ */