nvme-print: suppress output when no ctrl is present for list-subsys

When using list-subsys with the optional device filter argument, the
subsystem might not have any controller associated anymore, it was
filtered out. Avoid outputting any whitespace (or empty json data
structures) in this case.

Signed-off-by: Daniel Wagner <[email protected]>

Author: igaw

nvme-print-json.c

@@ -2558,6 +2558,14 @@ static void json_print_nvme_subsystem_list(nvme_root_t r, bool show_ana)
 			obj_add_str(host_attrs, "HostID", hostid);
 		subsystems = json_create_array();
 		nvme_for_each_subsystem(h, s) {
+			nvme_ctrl_t c;
+			bool no_ctrl = true;
+
+			nvme_subsystem_for_each_ctrl(s, c)
+				no_ctrl = false;
+			if (no_ctrl)
+				continue;
+
 			subsystem_attrs = json_create_object();
 			obj_add_str(subsystem_attrs, "Name", nvme_subsystem_get_name(s));
 			obj_add_str(subsystem_attrs, "NQN", nvme_subsystem_get_nqn(s));

nvme-print-stdout.c

@@ -1132,8 +1132,15 @@ static void stdout_subsystem(nvme_root_t r, bool show_ana)
 
 	nvme_for_each_host(r, h) {
 		nvme_subsystem_t s;
+		nvme_ctrl_t c;
+		bool no_ctrl = true;
 
 		nvme_for_each_subsystem(h, s) {
+			nvme_subsystem_for_each_ctrl(s, c)
+				no_ctrl = false;
+			if (no_ctrl)
+				continue;
+
 			if (!first)
 				printf("\n");
 			first = false;