fix(dataman_client): fail fast when dataman is unavailable (#26652)

* fix(dataman_client): fail fast when dataman is unavailable

Check client_id before every DatamanClient operation to avoid waiting
for a response timeout when dataman was never running.

- Adds CLIENT_ID_NOT_SET guard to all sync and async methods
- Avoids cross-module linkage between dataman_client lib and dataman module

Supersedes #26128

* better init

src/lib/dataman_client/DatamanClient.cpp

@@ -148,6 +148,10 @@ bool DatamanClient::syncHandler(const dataman_request_s &request, dataman_respon
 
 bool DatamanClient::readSync(dm_item_t item, uint32_t index, uint8_t *buffer, uint32_t length, hrt_abstime timeout)
 {
+	if (_client_id == CLIENT_ID_NOT_SET) {
+		return false;
+	}
+
 	if (length > g_per_item_size[item]) {
 		PX4_ERR("Length  %" PRIu32 " can't fit in data size for item  %" PRIi8, length, static_cast<uint8_t>(item));
 		return false;
@@ -184,6 +188,10 @@ bool DatamanClient::readSync(dm_item_t item, uint32_t index, uint8_t *buffer, ui
 
 bool DatamanClient::writeSync(dm_item_t item, uint32_t index, uint8_t *buffer, uint32_t length, hrt_abstime timeout)
 {
+	if (_client_id == CLIENT_ID_NOT_SET) {
+		return false;
+	}
+
 	if (length > g_per_item_size[item]) {
 		PX4_ERR("Length  %" PRIu32 " can't fit in data size for item  %" PRIi8, length, static_cast<uint8_t>(item));
 		return false;
@@ -219,6 +227,10 @@ bool DatamanClient::writeSync(dm_item_t item, uint32_t index, uint8_t *buffer, u
 
 bool DatamanClient::clearSync(dm_item_t item, hrt_abstime timeout)
 {
+	if (_client_id == CLIENT_ID_NOT_SET) {
+		return false;
+	}
+
 	hrt_abstime timestamp = hrt_absolute_time();
 
 	dataman_request_s request;
@@ -245,6 +257,10 @@ bool DatamanClient::clearSync(dm_item_t item, hrt_abstime timeout)
 
 bool DatamanClient::readAsync(dm_item_t item, uint32_t index, uint8_t *buffer, uint32_t length)
 {
+	if (_client_id == CLIENT_ID_NOT_SET) {
+		return false;
+	}
+
 	if (length > g_per_item_size[item]) {
 		PX4_ERR("Length  %" PRIu32 " can't fit in data size for item  %" PRIi8, length, static_cast<uint8_t>(item));
 		return false;
@@ -283,6 +299,10 @@ bool DatamanClient::readAsync(dm_item_t item, uint32_t index, uint8_t *buffer, u
 
 bool DatamanClient::writeAsync(dm_item_t item, uint32_t index, uint8_t *buffer, uint32_t length)
 {
+	if (_client_id == CLIENT_ID_NOT_SET) {
+		return false;
+	}
+
 	if (length > g_per_item_size[item]) {
 		PX4_ERR("Length  %" PRIu32 " can't fit in data size for item  %" PRIi8, length, static_cast<uint8_t>(item));
 		return false;
@@ -323,6 +343,10 @@ bool DatamanClient::writeAsync(dm_item_t item, uint32_t index, uint8_t *buffer,
 
 bool DatamanClient::clearAsync(dm_item_t item)
 {
+	if (_client_id == CLIENT_ID_NOT_SET) {
+		return false;
+	}
+
 	bool success = false;
 
 	if (_state == State::Idle) {

src/lib/dataman_client/DatamanClient.hpp

@@ -183,11 +183,11 @@ private:
 
 	px4_pollfd_struct_t _fds;
 
-	uint8_t _client_id{0};
+	static constexpr uint8_t CLIENT_ID_NOT_SET{0};
+
+	uint8_t _client_id{CLIENT_ID_NOT_SET};
 
 	perf_counter_t _sync_perf{nullptr};
-
-	static constexpr uint8_t CLIENT_ID_NOT_SET{0};
 };