net: lwm2m: Add ObjLnk resource type support

Implement LWM2M ObjLnk resource type and plaintext, TLV and JSON
readers/writers.

Signed-off-by: Robert Lubos <robert.lubos@nordicsemi.no>

doc/reference/networking/lwm2m.rst

@@ -216,7 +216,7 @@ Example LwM2M object and resources: Device
      - R
      - Multiple
      - Optional
-     - ObjLink
+     - ObjLnk
 
 The server could query the ``Manufacturer`` resource for ``Device`` object
 instance 0 (the default and only instance) by sending a ``READ 3/0/0``

include/net/lwm2m.h

@@ -341,6 +341,19 @@ typedef struct float64_value {
 	int64_t val2;
 } float64_value_t;
 
+/**
+ * @brief Maximum value for ObjLnk resource fields
+ */
+#define LWM2M_OBJLNK_MAX_ID USHRT_MAX
+
+/**
+ * @brief LWM2M ObjLnk resource type structure
+ */
+struct lwm2m_objlnk {
+	uint16_t obj_id;
+	uint16_t obj_inst;
+};
+
 /**
  * @brief Create an LwM2M object instance.
  *
@@ -485,6 +498,16 @@ int lwm2m_engine_set_float32(char *pathstr, float32_value_t *value);
  */
 int lwm2m_engine_set_float64(char *pathstr, float64_value_t *value);
 
+/**
+ * @brief Set resource (instance) value (ObjLnk)
+ *
+ * @param[in] pathstr LwM2M path string "obj/obj-inst/res(/res-inst)"
+ * @param[in] value pointer to the lwm2m_objlnk structure
+ *
+ * @return 0 for success or negative in case of error.
+ */
+int lwm2m_engine_set_objlnk(char *pathstr, struct lwm2m_objlnk *value);
+
 /**
  * @brief Get resource (instance) value (opaque buffer)
  *
@@ -617,6 +640,17 @@ int lwm2m_engine_get_float32(char *pathstr, float32_value_t *buf);
  */
 int lwm2m_engine_get_float64(char *pathstr, float64_value_t *buf);
 
+/**
+ * @brief Get resource (instance) value (ObjLnk)
+ *
+ * @param[in] pathstr LwM2M path string "obj/obj-inst/res(/res-inst)"
+ * @param[out] buf lwm2m_objlnk buffer to copy data into
+ *
+ * @return 0 for success or negative in case of error.
+ */
+int lwm2m_engine_get_objlnk(char *pathstr, struct lwm2m_objlnk *buf);
+
+
 /**
  * @brief Set resource (instance) read callback
  *

subsys/net/lib/lwm2m/lwm2m_engine.c

@@ -12,11 +12,6 @@
  *         Joel Hoglund <joel@sics.se>
  */
 
-/*
- * TODO:
- * - Handle Resource ObjLink type
- */
-
 #define LOG_MODULE_NAME net_lwm2m_engine
 #define LOG_LEVEL CONFIG_LWM2M_LOG_LEVEL
 
@@ -1501,6 +1496,11 @@ static int lwm2m_engine_set(char *pathstr, void *value, uint16_t len)
 				((float64_value_t *)value)->val2;
 		break;
 
+	case LWM2M_RES_TYPE_OBJLNK:
+		*((struct lwm2m_objlnk *)data_ptr) =
+				*(struct lwm2m_objlnk *)value;
+		break;
+
 	default:
 		LOG_ERR("unknown obj data_type %d", obj_field->data_type);
 		return -EINVAL;
@@ -1587,6 +1587,11 @@ int lwm2m_engine_set_float64(char *pathstr, float64_value_t *value)
 	return lwm2m_engine_set(pathstr, value, sizeof(float64_value_t));
 }
 
+int lwm2m_engine_set_objlnk(char *pathstr, struct lwm2m_objlnk *value)
+{
+	return lwm2m_engine_set(pathstr, value, sizeof(struct lwm2m_objlnk));
+}
+
 /* user data getter functions */
 
 int lwm2m_engine_get_res_data(char *pathstr, void **data_ptr, uint16_t *data_len,
@@ -1739,6 +1744,11 @@ static int lwm2m_engine_get(char *pathstr, void *buf, uint16_t buflen)
 				((float64_value_t *)data_ptr)->val2;
 			break;
 
+		case LWM2M_RES_TYPE_OBJLNK:
+			*(struct lwm2m_objlnk *)buf =
+				*(struct lwm2m_objlnk *)data_ptr;
+			break;
+
 		default:
 			LOG_ERR("unknown obj data_type %d",
 				obj_field->data_type);
@@ -1823,6 +1833,11 @@ int lwm2m_engine_get_float64(char *pathstr, float64_value_t *buf)
 	return lwm2m_engine_get(pathstr, buf, sizeof(float64_value_t));
 }
 
+int lwm2m_engine_get_objlnk(char *pathstr, struct lwm2m_objlnk *buf)
+{
+	return lwm2m_engine_get(pathstr, buf, sizeof(struct lwm2m_objlnk));
+}
+
 int lwm2m_engine_get_resource(char *pathstr, struct lwm2m_engine_res **res)
 {
 	int ret;
@@ -2159,6 +2174,11 @@ static int lwm2m_read_handler(struct lwm2m_engine_obj_inst *obj_inst,
 				(float64_value_t *)data_ptr);
 			break;
 
+		case LWM2M_RES_TYPE_OBJLNK:
+			engine_put_objlnk(&msg->out, &msg->path,
+					  (struct lwm2m_objlnk *)data_ptr);
+			break;
+
 		default:
 			LOG_ERR("unknown obj data_type %d",
 				obj_field->data_type);
@@ -2386,6 +2406,12 @@ int lwm2m_write_handler(struct lwm2m_engine_obj_inst *obj_inst,
 			len = sizeof(float64_value_t);
 			break;
 
+		case LWM2M_RES_TYPE_OBJLNK:
+			engine_get_objlnk(&msg->in,
+					  (struct lwm2m_objlnk *)data_ptr);
+			len = sizeof(struct lwm2m_objlnk);
+			break;
+
 		default:
 			LOG_ERR("unknown obj data_type %d",
 				obj_field->data_type);

subsys/net/lib/lwm2m/lwm2m_object.h

@@ -124,6 +124,7 @@
 #define LWM2M_RES_TYPE_TIME	12
 #define LWM2M_RES_TYPE_FLOAT32	13
 #define LWM2M_RES_TYPE_FLOAT64	14
+#define LWM2M_RES_TYPE_OBJLNK	15
 
 /* remember that we have already output a value - can be between two block's */
 #define WRITER_OUTPUT_VALUE      1
@@ -470,6 +471,9 @@ struct lwm2m_writer {
 	size_t (*put_opaque)(struct lwm2m_output_context *out,
 			     struct lwm2m_obj_path *path,
 			     char *buf, size_t buflen);
+	size_t (*put_objlnk)(struct lwm2m_output_context *out,
+			     struct lwm2m_obj_path *path,
+			     struct lwm2m_objlnk *value);
 };
 
 struct lwm2m_reader {
@@ -487,6 +491,8 @@ struct lwm2m_reader {
 			   bool *value);
 	size_t (*get_opaque)(struct lwm2m_input_context *in,
 			     uint8_t *buf, size_t buflen, bool *last_block);
+	size_t (*get_objlnk)(struct lwm2m_input_context *in,
+			     struct lwm2m_objlnk *value);
 };
 
 /* output user_data management functions */
@@ -674,6 +680,13 @@ static inline size_t engine_put_opaque(struct lwm2m_output_context *out,
 	return 0;
 }
 
+static inline size_t engine_put_objlnk(struct lwm2m_output_context *out,
+				       struct lwm2m_obj_path *path,
+				       struct lwm2m_objlnk *value)
+{
+	return out->writer->put_objlnk(out, path, value);
+}
+
 static inline size_t engine_get_s32(struct lwm2m_input_context *in,
 				    int32_t *value)
 {
@@ -721,4 +734,10 @@ static inline size_t engine_get_opaque(struct lwm2m_input_context *in,
 	return 0;
 }
 
+static inline size_t engine_get_objlnk(struct lwm2m_input_context *in,
+				       struct lwm2m_objlnk *value)
+{
+	return in->reader->get_objlnk(in, value);
+}
+
 #endif /* LWM2M_OBJECT_H_ */

subsys/net/lib/lwm2m/lwm2m_rw_json.c

@@ -526,6 +526,20 @@ static size_t put_bool(struct lwm2m_output_context *out,
 	return (size_t)len;
 }
 
+static size_t put_objlnk(struct lwm2m_output_context *out,
+			 struct lwm2m_obj_path *path,
+			 struct lwm2m_objlnk *value)
+{
+	size_t len;
+
+	len = put_json_prefix(out, path, "\"ov\"");
+	len += plain_text_put_format(out, "\"%u:%u\"", value->obj_id,
+				     value->obj_inst);
+	len += put_json_postfix(out);
+
+	return len;
+}
+
 static size_t read_number(struct lwm2m_input_context *in,
 			  int64_t *value1, int64_t *value2,
 			  bool accept_sign, bool accept_dot)
@@ -676,6 +690,37 @@ static size_t get_opaque(struct lwm2m_input_context *in,
 	return 0;
 }
 
+static size_t get_objlnk(struct lwm2m_input_context *in,
+			 struct lwm2m_objlnk *value)
+{
+	int64_t tmp;
+	size_t len;
+	uint16_t value_offset;
+	struct json_in_formatter_data *fd;
+
+	fd = engine_get_in_user_data(in);
+	if (!fd) {
+		return 0;
+	}
+
+	/* Store the original value offset. */
+	value_offset = fd->value_offset;
+
+	len = read_number(in, &tmp, NULL, false, false);
+	value->obj_id = (uint16_t)tmp;
+
+	len++;  /* +1 for ':' delimeter. */
+	fd->value_offset += len;
+
+	len += read_number(in, &tmp, NULL, false, false);
+	value->obj_inst = (uint16_t)tmp;
+
+	/* Restore the original value offset. */
+	fd->value_offset = value_offset;
+
+	return len;
+}
+
 const struct lwm2m_writer json_writer = {
 	.put_begin = put_begin,
 	.put_end = put_end,
@@ -689,6 +734,7 @@ const struct lwm2m_writer json_writer = {
 	.put_float32fix = put_float32fix,
 	.put_float64fix = put_float64fix,
 	.put_bool = put_bool,
+	.put_objlnk = put_objlnk,
 };
 
 const struct lwm2m_reader json_reader = {
@@ -699,6 +745,7 @@ const struct lwm2m_reader json_reader = {
 	.get_float64fix = get_float64fix,
 	.get_bool = get_bool,
 	.get_opaque = get_opaque,
+	.get_objlnk = get_objlnk,
 };
 
 int do_read_op_json(struct lwm2m_message *msg, int content_format)

subsys/net/lib/lwm2m/lwm2m_rw_oma_tlv.c

@@ -566,6 +566,15 @@ static size_t put_opaque(struct lwm2m_output_context *out,
 	return put_string(out, path, buf, buflen);
 }
 
+static size_t put_objlnk(struct lwm2m_output_context *out,
+			 struct lwm2m_obj_path *path,
+			 struct lwm2m_objlnk *value)
+{
+	int32_t value_s32 = (value->obj_id << 16) | value->obj_inst;
+
+	return put_s32(out, path, value_s32);
+}
+
 static size_t get_number(struct lwm2m_input_context *in, int64_t *value,
 			 uint8_t max_len)
 {
@@ -758,6 +767,20 @@ static size_t get_opaque(struct lwm2m_input_context *in,
 	return lwm2m_engine_get_opaque_more(in, value, buflen, last_block);
 }
 
+static size_t get_objlnk(struct lwm2m_input_context *in,
+			 struct lwm2m_objlnk *value)
+{
+	int32_t value_s32;
+	size_t size;
+
+	size = get_s32(in, &value_s32);
+
+	value->obj_id = (value_s32 >> 16) & 0xFFFF;
+	value->obj_inst = value_s32 && 0xFFFF;
+
+	return size;
+}
+
 const struct lwm2m_writer oma_tlv_writer = {
 	.put_begin_oi = put_begin_oi,
 	.put_end_oi = put_end_oi,
@@ -772,6 +795,7 @@ const struct lwm2m_writer oma_tlv_writer = {
 	.put_float64fix = put_float64fix,
 	.put_bool = put_bool,
 	.put_opaque = put_opaque,
+	.put_objlnk = put_objlnk,
 };
 
 const struct lwm2m_reader oma_tlv_reader = {
@@ -782,6 +806,7 @@ const struct lwm2m_reader oma_tlv_reader = {
 	.get_float64fix = get_float64fix,
 	.get_bool = get_bool,
 	.get_opaque = get_opaque,
+	.get_objlnk = get_objlnk,
 };
 
 int do_read_op_tlv(struct lwm2m_message *msg, int content_format)

subsys/net/lib/lwm2m/lwm2m_rw_plain_text.c

@@ -194,6 +194,14 @@ static size_t put_bool(struct lwm2m_output_context *out,
 	}
 }
 
+static size_t put_objlnk(struct lwm2m_output_context *out,
+			 struct lwm2m_obj_path *path,
+			 struct lwm2m_objlnk *value)
+{
+	return plain_text_put_format(out, "%u:%u", value->obj_id,
+				     value->obj_inst);
+}
+
 static int get_length_left(struct lwm2m_input_context *in)
 {
 	return in->in_cpkt->offset - in->offset;
@@ -330,6 +338,26 @@ static size_t get_opaque(struct lwm2m_input_context *in,
 	return lwm2m_engine_get_opaque_more(in, value, buflen, last_block);
 }
 
+
+static size_t get_objlnk(struct lwm2m_input_context *in,
+			 struct lwm2m_objlnk *value)
+{
+	int64_t tmp;
+	size_t len;
+
+	len = plain_text_read_number(in, &tmp, NULL, false, false);
+	value->obj_id = (uint16_t)tmp;
+
+	/* Skip ':' delimeter. */
+	in->offset++;
+	len++;
+
+	len += plain_text_read_number(in, &tmp, NULL, false, false);
+	value->obj_inst = (uint16_t)tmp;
+
+	return len;
+}
+
 const struct lwm2m_writer plain_text_writer = {
 	.put_s8 = put_s8,
 	.put_s16 = put_s16,
@@ -339,6 +367,7 @@ const struct lwm2m_writer plain_text_writer = {
 	.put_float32fix = plain_text_put_float32fix,
 	.put_float64fix = plain_text_put_float64fix,
 	.put_bool = put_bool,
+	.put_objlnk = put_objlnk,
 };
 
 const struct lwm2m_reader plain_text_reader = {
@@ -349,6 +378,7 @@ const struct lwm2m_reader plain_text_reader = {
 	.get_float64fix = get_float64fix,
 	.get_bool = get_bool,
 	.get_opaque = get_opaque,
+	.get_objlnk = get_objlnk,
 };
 
 int do_read_op_plain_text(struct lwm2m_message *msg, int content_format)