diff --git a/include/patchelfcrc/crc-output-struct.h b/include/patchelfcrc/crc-output-struct.h
index 34ed808..4fddc03 100644
--- a/include/patchelfcrc/crc-output-struct.h
+++ b/include/patchelfcrc/crc-output-struct.h
@@ -3,14 +3,30 @@
 
 #include <stdint.h>
 
+/**
+ * @brief Expected size of @ref crc_out_struct_32bit.
+ * @note If the size of the structure does not match this number, structure padding occured which should not happen.
+ */
 #define CRC_OUT_STRUCT_SIZE_32BIT 12u
+
+/**
+ * @brief output structure of CRCs in a 32bit executable
+*/
 struct crc_out_struct_32bit {
 	uint32_t start_address;	/**< @brief Start address of struct*/
 	uint32_t length; 	/**< @brief Length of section in bytes */
 	uint32_t crc;		/**< @brief LSB aligned CRC */
 };
 
+/**
+ * @brief Expected size of @ref crc_out_struct_64bit.
+ * @note If the size of the structure does not match this number, structure padding occured which should not happen.
+ */
 #define CRC_OUT_STRUCT_SIZE_64BIT 24u
+
+/**
+ * @brief output structure of CRCs in a 64bit executable
+ */
 struct crc_out_struct_64bit {
 	uint64_t start_address;	/**< @brief Start address of struct*/
 	uint64_t length; 	/**< @brief Length of section in bytes */
@@ -18,6 +34,9 @@ struct crc_out_struct_64bit {
     uint32_t _unused_dummy;	/**< @brief Dummy. Do not use, it prevents misalignments */
 };
 
+/**
+ * @brief Trigger compile error if condition is false
+ */
 #define BUILD_ASSERT(cond) ((void)sizeof(char[1 - 2 * !!(cond)]))
 
 /**
diff --git a/main.c b/main.c
index c95093d..256f32a 100644
--- a/main.c
+++ b/main.c
@@ -117,6 +117,15 @@ static error_t parse_opt(int key, char *arg, struct argp_state *state)
 	case 'O':
 		args->output_section = arg;
 		break;
+	case 'r':
+		args->crc.rev = true;
+		break;
+	case 's':
+		args->crc.start_value = strtoul(arg, NULL, 0);
+		break;
+	case 'x':
+		args->crc.xor = strtoul(arg, NULL, 0);
+		break;
 	case ARGP_KEY_ARG:
 		if (state->arg_num >= 1)
 			argp_usage(state);