nvme: support <device> option in show-topology command

Although the help text for the nvme show-topology command indicates
support for a <device> option, this option has no effect in practice
— specifying an NVMe device name does not filter the output.

This commit adds proper support for the <device> option, enabling users
to filter the topology output based on the specified NVMe device.

Reviewed-by: Hannes Reinecke <[email protected]>
Signed-off-by: Nilay Shroff <[email protected]>

Author: shroffni

nvme-print-stdout.c

@@ -5683,6 +5683,15 @@ static void stdout_simple_topology(nvme_root_t r,
 
 	nvme_for_each_host(r, h) {
 		nvme_for_each_subsystem(h, s) {
+			bool no_ctrl = true;
+			nvme_ctrl_t c;
+
+			nvme_subsystem_for_each_ctrl(s, c)
+				no_ctrl = false;
+
+			if (no_ctrl)
+				continue;
+
 			if (!first)
 				printf("\n");
 			first = false;

nvme.c

@@ -10207,6 +10207,8 @@ static int show_topology_cmd(int argc, char **argv, struct command *command, str
 	const char *ranking = "Ranking order: namespace|ctrl";
 	nvme_print_flags_t flags;
 	_cleanup_nvme_root_ nvme_root_t r = NULL;
+	char *devname = NULL;
+	nvme_scan_filter_t filter = NULL;
 	enum nvme_cli_topo_ranking rank;
 	int err;
 
@@ -10249,7 +10251,20 @@ static int show_topology_cmd(int argc, char **argv, struct command *command, str
 		return -errno;
 	}
 
-	err = nvme_scan_topology(r, NULL, NULL);
+	if (optind < argc)
+		devname = basename(argv[optind++]);
+
+	if (devname) {
+		int subsys_id, nsid;
+
+		if (sscanf(devname, "nvme%dn%d", &subsys_id, &nsid) != 2) {
+			nvme_show_error("Invalid device name %s\n", devname);
+			return -EINVAL;
+		}
+		filter = nvme_match_device_filter;
+	}
+
+	err = nvme_scan_topology(r, filter, (void *)devname);
 	if (err < 0) {
 		nvme_show_error("Failed to scan topology: %s", nvme_strerror(errno));
 		return err;