Bluetooth: Host: Define bt_att_err_to_str()

This can be useful if application developers
want to print them in the applications.

Later we can also use them in
the host to improve debuggability.

Signed-off-by: Rubin Gerritsen <[email protected]>

include/zephyr/bluetooth/att.h

@@ -101,6 +101,22 @@ extern "C" {
 #define BT_ATT_LAST_ATTRIBUTE_HANDLE            0xffff
 #define BT_ATT_LAST_ATTTRIBUTE_HANDLE __DEPRECATED_MACRO BT_ATT_LAST_ATTRIBUTE_HANDLE
 
+/** Converts a ATT error to string.
+ *
+ * The error codes are described in the Bluetooth Core specification,
+ * Vol 3, Part F, Section 3.4.1.1 and in
+ * The Supplement to the Bluetooth Core Specification (CSS), v11,
+ * Part B, Section 1.2.
+ *
+ * The ATT and GATT documentation found in Vol 4, Part F and
+ * Part G describe when the different error codes are used.
+ *
+ * See also the defined BT_ATT_ERR_* macros.
+ *
+ * @return The string representation of the ATT error code.
+ */
+const char *bt_att_err_to_str(uint8_t att_err);
+
 #if defined(CONFIG_BT_EATT)
 #if defined(CONFIG_BT_TESTING)
 

subsys/bluetooth/host/att.c

@@ -185,6 +185,61 @@ static struct bt_att_tx_meta_data tx_meta_data_storage[CONFIG_BT_ATT_TX_COUNT];
 struct bt_att_tx_meta_data *bt_att_get_tx_meta_data(const struct net_buf *buf);
 static void att_on_sent_cb(struct bt_att_tx_meta_data *meta);
 
+
+const char *bt_att_err_to_str(uint8_t att_err)
+{
+	/* To mapping tables are used to avoid a big gap with NULL-entries. */
+	#define ATT_ERR(err) [err] = #err
+	#define ATT_ERR_SECOND(err) [err - BT_ATT_ERR_WRITE_REQ_REJECTED] = #err
+
+	const char * const first_mapping_table[] = {
+		ATT_ERR(BT_ATT_ERR_SUCCESS),
+		ATT_ERR(BT_ATT_ERR_INVALID_HANDLE),
+		ATT_ERR(BT_ATT_ERR_READ_NOT_PERMITTED),
+		ATT_ERR(BT_ATT_ERR_WRITE_NOT_PERMITTED),
+		ATT_ERR(BT_ATT_ERR_INVALID_PDU),
+		ATT_ERR(BT_ATT_ERR_AUTHENTICATION),
+		ATT_ERR(BT_ATT_ERR_NOT_SUPPORTED),
+		ATT_ERR(BT_ATT_ERR_INVALID_OFFSET),
+		ATT_ERR(BT_ATT_ERR_AUTHORIZATION),
+		ATT_ERR(BT_ATT_ERR_PREPARE_QUEUE_FULL),
+		ATT_ERR(BT_ATT_ERR_ATTRIBUTE_NOT_FOUND),
+		ATT_ERR(BT_ATT_ERR_ATTRIBUTE_NOT_LONG),
+		ATT_ERR(BT_ATT_ERR_ENCRYPTION_KEY_SIZE),
+		ATT_ERR(BT_ATT_ERR_INVALID_ATTRIBUTE_LEN),
+		ATT_ERR(BT_ATT_ERR_UNLIKELY),
+		ATT_ERR(BT_ATT_ERR_INSUFFICIENT_ENCRYPTION),
+		ATT_ERR(BT_ATT_ERR_UNSUPPORTED_GROUP_TYPE),
+		ATT_ERR(BT_ATT_ERR_INSUFFICIENT_RESOURCES),
+		ATT_ERR(BT_ATT_ERR_DB_OUT_OF_SYNC),
+		ATT_ERR(BT_ATT_ERR_VALUE_NOT_ALLOWED),
+	};
+
+	const char * const second_mapping_table[] = {
+		ATT_ERR_SECOND(BT_ATT_ERR_WRITE_REQ_REJECTED),
+		ATT_ERR_SECOND(BT_ATT_ERR_CCC_IMPROPER_CONF),
+		ATT_ERR_SECOND(BT_ATT_ERR_PROCEDURE_IN_PROGRESS),
+		ATT_ERR_SECOND(BT_ATT_ERR_OUT_OF_RANGE),
+	};
+
+
+	if (att_err < ARRAY_SIZE(first_mapping_table) && first_mapping_table[att_err]) {
+		return first_mapping_table[att_err];
+	} else if (att_err >= BT_ATT_ERR_WRITE_REQ_REJECTED) {
+		const uint8_t second_index = att_err - BT_ATT_ERR_WRITE_REQ_REJECTED;
+
+		if (second_index < ARRAY_SIZE(second_mapping_table) &&
+		    second_mapping_table[second_index]) {
+			return second_mapping_table[second_index];
+		}
+	}
+
+	return "(unknown)";
+
+	#undef ATT_ERR
+	#undef ATT_ERR_SECOND
+}
+
 static void att_tx_destroy(struct net_buf *buf)
 {
 	struct bt_att_tx_meta_data *p_meta = bt_att_get_tx_meta_data(buf);

tests/bluetooth/gatt/src/main.c

@@ -274,3 +274,24 @@ ZTEST(test_gatt, test_gatt_write)
 	zassert_mem_equal(value, test_value, ret,
 			  "Attribute write value don't match");
 }
+
+ZTEST(test_gatt, test_bt_att_err_to_str)
+{
+	/* Test a couple of entries */
+	zassert_str_equal(bt_att_err_to_str(BT_ATT_ERR_SUCCESS),
+			  "BT_ATT_ERR_SUCCESS");
+	zassert_str_equal(bt_att_err_to_str(BT_ATT_ERR_INSUFFICIENT_ENCRYPTION),
+			  "BT_ATT_ERR_INSUFFICIENT_ENCRYPTION");
+	zassert_str_equal(bt_att_err_to_str(BT_ATT_ERR_OUT_OF_RANGE),
+			  "BT_ATT_ERR_OUT_OF_RANGE");
+
+	/* Test a entries that is not used */
+	zassert_mem_equal(bt_att_err_to_str(0x14),
+			  "(unknown)", strlen("(unknown)"));
+	zassert_mem_equal(bt_att_err_to_str(0xFB),
+			  "(unknown)", strlen("(unknown)"));
+
+	for (uint16_t i = 0; i <= UINT8_MAX; i++) {
+		zassert_not_null(bt_att_err_to_str(i), ": %d", i);
+	}
+}