Index: cam/cam_xpt.h
===================================================================
--- cam/cam_xpt.h	(revision 220981)
+++ cam/cam_xpt.h	(working copy)
@@ -113,6 +113,7 @@
 path_id_t		xpt_path_path_id(struct cam_path *path);
 target_id_t		xpt_path_target_id(struct cam_path *path);
 lun_id_t		xpt_path_lun_id(struct cam_path *path);
+int			xpt_path_legacy_ata_id(struct cam_path *path);
 struct cam_sim		*xpt_path_sim(struct cam_path *path);
 struct cam_periph	*xpt_path_periph(struct cam_path *path);
 void			xpt_async(u_int32_t async_code, struct cam_path *path,
Index: cam/ata/ata_da.c
===================================================================
--- cam/ata/ata_da.c	(revision 220981)
+++ cam/ata/ata_da.c	(working copy)
@@ -183,6 +183,10 @@
 static void		adasuspend(void *arg);
 static void		adaresume(void *arg);
 
+#ifndef	ADA_DEFAULT_LEGACY_ALIASES
+#define	ADA_DEFAULT_LEGACY_ALIASES	1
+#endif
+
 #ifndef ADA_DEFAULT_TIMEOUT
 #define ADA_DEFAULT_TIMEOUT 30	/* Timeout in seconds */
 #endif
@@ -215,6 +219,7 @@
 #define	ata_disk_firmware_geom_adjust(disk)
 #endif
 
+static int ada_legacy_aliases = ADA_DEFAULT_LEGACY_ALIASES;
 static int ada_retry_count = ADA_DEFAULT_RETRY;
 static int ada_default_timeout = ADA_DEFAULT_TIMEOUT;
 static int ada_send_ordered = ADA_DEFAULT_SEND_ORDERED;
@@ -224,6 +229,9 @@
 
 SYSCTL_NODE(_kern_cam, OID_AUTO, ada, CTLFLAG_RD, 0,
             "CAM Direct Access Disk driver");
+SYSCTL_INT(_kern_cam_ada, OID_AUTO, legacy_aliases, CTLFLAG_RW,
+           &ada_legacy_aliases, 0, "Create legacy-like device aliases");
+TUNABLE_INT("kern.cam.ada.legacy_aliases", &ada_legacy_aliases);
 SYSCTL_INT(_kern_cam_ada, OID_AUTO, retry_count, CTLFLAG_RW,
            &ada_retry_count, 0, "Normal I/O retry count");
 TUNABLE_INT("kern.cam.ada.retry_count", &ada_retry_count);
@@ -723,10 +731,11 @@
 	struct ada_softc *softc;
 	struct ccb_pathinq cpi;
 	struct ccb_getdev *cgd;
-	char   announce_buf[80];
+	char   announce_buf[80], buf1[32];
 	struct disk_params *dp;
 	caddr_t match;
 	u_int maxio;
+	int legacy_id;
 
 	cgd = (struct ccb_getdev *)arg;
 	if (periph == NULL) {
@@ -861,6 +870,18 @@
 	softc->disk->d_fwheads = softc->params.heads;
 	ata_disk_firmware_geom_adjust(softc->disk);
 
+	if (ada_legacy_aliases) {
+		legacy_id = xpt_path_legacy_ata_id(periph->path);
+		if (legacy_id >= 0) {
+			snprintf(announce_buf, sizeof(announce_buf),
+			    "kern.devalias.%s%d",
+			    softc->disk->d_name, softc->disk->d_unit);
+			snprintf(buf1, sizeof(buf1),
+			    "ad%d", legacy_id);
+			setenv(announce_buf, buf1);
+		}
+	} else
+		legacy_id = -1;
 	disk_create(softc->disk, DISK_VERSION);
 	mtx_lock(periph->sim->mtx);
 	cam_periph_unhold(periph);
@@ -874,6 +895,9 @@
 		dp->secsize, dp->heads,
 		dp->secs_per_track, dp->cylinders);
 	xpt_announce_periph(periph, announce_buf);
+	if (legacy_id >= 0)
+		printf("%s%d: Previously was known as ad%d\n",
+		       periph->periph_name, periph->unit_number, legacy_id);
 
 	/*
 	 * Create our sysctl variables, now that we know
Index: cam/cam_xpt.c
===================================================================
--- cam/cam_xpt.c	(revision 220981)
+++ cam/cam_xpt.c	(working copy)
@@ -3569,6 +3569,42 @@
 	return (path->periph);
 }
 
+int
+xpt_path_legacy_ata_id(struct cam_path *path)
+{
+	struct cam_eb *bus;
+	int bus_id;
+
+	if ((strcmp(path->bus->sim->sim_name, "ata") != 0) &&
+	    strcmp(path->bus->sim->sim_name, "ahcich") != 0 &&
+	    strcmp(path->bus->sim->sim_name, "mvsch") != 0 &&
+	    strcmp(path->bus->sim->sim_name, "siisch") != 0)
+		return (-1);
+
+	if (strcmp(path->bus->sim->sim_name, "ata") == 0 &&
+	    path->bus->sim->unit_number < 2) {
+		bus_id = path->bus->sim->unit_number;
+	} else {
+		bus_id = 2;
+		xpt_lock_buses();
+		TAILQ_FOREACH(bus, &xsoftc.xpt_busses, links) {
+			if (bus == path->bus)
+				break;
+			if ((strcmp(bus->sim->sim_name, "ata") == 0 &&
+			     bus->sim->unit_number >= 2) ||
+			    strcmp(bus->sim->sim_name, "ahcich") == 0 ||
+			    strcmp(bus->sim->sim_name, "mvsch") == 0 ||
+			    strcmp(bus->sim->sim_name, "siisch") == 0)
+				bus_id++;
+		}
+		xpt_unlock_buses();
+	}
+	if (path->target != NULL)
+		return (bus_id * 2 + path->target->target_id);
+	else
+		return (bus_id * 2);
+}
+
 /*
  * Release a CAM control block for the caller.  Remit the cost of the structure
  * to the device referenced by the path.  If the this device had no 'credits'
Index: geom/geom_dev.c
===================================================================
--- geom/geom_dev.c	(revision 220981)
+++ geom/geom_dev.c	(working copy)
@@ -113,8 +113,9 @@
 {
 	struct g_geom *gp;
 	struct g_consumer *cp;
-	int error;
-	struct cdev *dev;
+	int error, len;
+	struct cdev *dev, *adev;
+	char buf[64], *val;
 
 	g_trace(G_T_TOPOLOGY, "dev_taste(%s,%s)", mp->name, pp->name);
 	g_topology_assert();
@@ -136,12 +137,35 @@
 		g_destroy_geom(gp);
 		return (NULL);
 	}
+
+	/* Search for device alias name and create it if found. */
+	adev = NULL;
+	for (len = MIN(strlen(gp->name), sizeof(buf) - 15); len > 0; len--) {
+		snprintf(buf, sizeof(buf), "kern.devalias.%s", gp->name);
+		buf[14 + len] = 0;
+		val = getenv(buf);
+		if (val != NULL) {
+			snprintf(buf, sizeof(buf), "%s%s",
+			    val, gp->name + len);
+			freeenv(val);
+			adev = make_dev_alias(dev, buf);
+			break;
+		}
+	}
+
 	if (pp->flags & G_PF_CANDELETE)
 		dev->si_flags |= SI_CANDELETE;
 	dev->si_iosize_max = MAXPHYS;
 	gp->softc = dev;
 	dev->si_drv1 = gp;
 	dev->si_drv2 = cp;
+	if (adev != NULL) {
+		if (pp->flags & G_PF_CANDELETE)
+			adev->si_flags |= SI_CANDELETE;
+		adev->si_iosize_max = MAXPHYS;
+		adev->si_drv1 = gp;
+		adev->si_drv2 = cp;
+	}
 	return (gp);
 }