blktap2: Add tap_ctl_find_minor

Slack 'tap-ctl find -t <type> -f <path>'.

Signed-off-by: Daniel Stodden <daniel.stodden@citrix.com>

tools/blktap2/control/tap-ctl-list.c

@@ -504,3 +504,33 @@ out:
 
 	return err;
 }
+
+int
+tap_ctl_find_minor(const char *type, const char *path)
+{
+	tap_list_t **list, **_entry;
+	int minor, err;
+
+	err = tap_ctl_list(&list);
+	if (err)
+		return err;
+
+	minor = -1;
+
+	for (_entry = list; *_entry != NULL; ++_entry) {
+		tap_list_t *entry  = *_entry;
+
+		if (type && (!entry->type || strcmp(entry->type, type)))
+			continue;
+
+		if (path && (!entry->path || strcmp(entry->path, path)))
+			continue;
+
+		minor = entry->minor;
+		break;
+	}
+
+	tap_ctl_free_list(list);
+
+	return minor >= 0 ? minor : -ENOENT;
+}

tools/blktap2/control/tap-ctl.h

@@ -77,6 +77,7 @@ int tap_ctl_get_driver_id(const char *handle);
 
 int tap_ctl_list(tap_list_t ***list);
 void tap_ctl_free_list(tap_list_t **list);
+int tap_ctl_find_minor(const char *type, const char *path);
 
 int tap_ctl_allocate(int *minor, char **devname);
 int tap_ctl_free(const int minor);