s390/dasd: Simplify uid string generation

There are two variants of the device uid string. One containing the
virtual device unit information table (vduit) identifying the device as
a virtual device located on a real device in a z/VM environment. The
other variant does not contain those additional information.

Simplify the string generation with a shorter check of an existing vduit
embedded in the snprintf() calls.

Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>
Reviewed-by: Stefan Haberland <sth@linux.ibm.com>
Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
Link: https://lore.kernel.org/r/20240208164248.540985-2-sth@linux.ibm.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/s390/block/dasd_devmap.c

@@ -1412,15 +1412,9 @@ dasd_uid_show(struct device *dev, struct device_attribute *attr, char *buf)
 			break;
 		}
 
-		if (strlen(uid.vduit) > 0)
-			snprintf(uid_string, sizeof(uid_string),
-				 "%s.%s.%04x.%s.%s",
-				 uid.vendor, uid.serial, uid.ssid, ua_string,
-				 uid.vduit);
-		else
-			snprintf(uid_string, sizeof(uid_string),
-				 "%s.%s.%04x.%s",
-				 uid.vendor, uid.serial, uid.ssid, ua_string);
+		snprintf(uid_string, sizeof(uid_string), "%s.%s.%04x.%s%s%s",
+			 uid.vendor, uid.serial, uid.ssid, ua_string,
+			 uid.vduit[0] ? "." : "", uid.vduit);
 	}
 	dasd_put_device(device);
 

drivers/s390/block/dasd_eckd.c

@@ -1072,22 +1072,14 @@ static void dasd_eckd_read_fc_security(struct dasd_device *device)
 	}
 }
 
-static void dasd_eckd_get_uid_string(struct dasd_conf *conf,
-				     char *print_uid)
+static void dasd_eckd_get_uid_string(struct dasd_conf *conf, char *print_uid)
 {
 	struct dasd_uid uid;
 
 	create_uid(conf, &uid);
-	if (strlen(uid.vduit) > 0)
-		snprintf(print_uid, DASD_UID_STRLEN,
-			 "%s.%s.%04x.%02x.%s",
-			 uid.vendor, uid.serial, uid.ssid,
-			 uid.real_unit_addr, uid.vduit);
-	else
-		snprintf(print_uid, DASD_UID_STRLEN,
-			 "%s.%s.%04x.%02x",
-			 uid.vendor, uid.serial, uid.ssid,
-			 uid.real_unit_addr);
+	snprintf(print_uid, DASD_UID_STRLEN, "%s.%s.%04x.%02x%s%s",
+		 uid.vendor, uid.serial, uid.ssid, uid.real_unit_addr,
+		 uid.vduit[0] ? "." : "", uid.vduit);
 }
 
 static int dasd_eckd_check_cabling(struct dasd_device *device,