Index: umsm.c
===================================================================
RCS file: /cvs/src/sys/dev/usb/umsm.c,v
retrieving revision 1.125
diff -u -p -r1.125 umsm.c
--- umsm.c	2 Apr 2023 23:57:57 -0000	1.125
+++ umsm.c	6 Apr 2023 09:21:35 -0000
@@ -101,6 +101,7 @@ struct umsm_type {
 #define	DEV_NORMAL	0x0000
 #define	DEV_HUAWEI	0x0001
 #define	DEV_TRUINSTALL	0x0002
+#define	DEV_SIERRA	0x0004
 #define	DEV_UMASS1	0x0010
 #define	DEV_UMASS2	0x0020
 #define	DEV_UMASS3	0x0040
@@ -271,6 +272,7 @@ static const struct umsm_type umsm_devs[
 	{{ USB_VENDOR_SIERRA, USB_PRODUCT_SIERRA_AIRCARD_340U}, 0},
 	{{ USB_VENDOR_SIERRA, USB_PRODUCT_SIERRA_AIRCARD_770S}, 0},
 	{{ USB_VENDOR_SIERRA, USB_PRODUCT_SIERRA_MC7455}, 0},
+	{{ USB_VENDOR_SIERRA, USB_PRODUCT_SIERRA_MC7700}, DEV_SIERRA},
 
 	{{ USB_VENDOR_SIMCOM, USB_PRODUCT_SIMCOM_SIM5320}, 0},
 	{{ USB_VENDOR_SIMCOM, USB_PRODUCT_SIMCOM_SIM7600E}, 0},
@@ -363,6 +365,17 @@ umsm_match(struct device *parent, void *
 		/* Interface 4 can be used as a network device */
 		if (uaa->ifaceno >= 4)
 			return UMATCH_NONE;
+	} else if (flag & DEV_SIERRA) {
+		/* Sierra Wireless layout */
+		switch (uaa->ifaceno) {
+		case 0:
+		case 2:
+		case 3:
+			/* Only umsm on specific interfaces */
+			break;
+		default:
+			return UMATCH_NONE;
+		}
 	}
 
 	return UMATCH_VENDOR_IFACESUBCLASS;