softintr_establish() allocates memory, even if doesn't sleep I'd like to
keep all allocations in the same place.

Use M_DEVBUF consistently for all memory chunks in the softc.

No need to check for NULL before calling free(9).

Make spacing coherent with the rest of the file when arguments passed to
a function do not fit in a line.

Index: dev/dt/dt_dev.c
===================================================================
RCS file: /cvs/src/sys/dev/dt/dt_dev.c,v
diff -u -p -r1.39 dt_dev.c
--- dev/dt/dt_dev.c	2 Nov 2024 17:03:12 -0000	1.39
+++ dev/dt/dt_dev.c	2 Nov 2024 17:09:42 -0000
@@ -206,11 +206,6 @@ dtopen(dev_t dev, int flags, int mode, s
 	TAILQ_INIT(&sc->ds_pcbs);
 	sc->ds_lastcpu = 0;
 	sc->ds_evtcnt = 0;
-	sc->ds_si = softintr_establish(IPL_SOFTCLOCK, dt_deferred_wakeup, sc);
-	if (sc->ds_si == NULL) {
-		dtfree(sc);
-		return ENOMEM;
-	}
 
 	SLIST_INSERT_HEAD(&dtdev_list, sc, ds_next);
 
@@ -233,7 +228,6 @@ dtclose(dev_t dev, int flags, int mode, 
 	SLIST_REMOVE(&dtdev_list, sc, dt_softc, ds_next);
 	dt_ioctl_record_stop(sc);
 	dt_pcb_purge(&sc->ds_pcbs);
-	softintr_disestablish(sc->ds_si);
 	dtfree(sc);
 
 	return 0;
@@ -364,8 +358,8 @@ dtalloc(void)
 		return NULL;
 
 	for (i = 0; i < ncpusfound; i++) {
-		dtev = mallocarray(DT_EVTRING_SIZE, sizeof(*dtev), M_DT,
-				   M_WAITOK|M_CANFAIL|M_ZERO);
+		dtev = mallocarray(DT_EVTRING_SIZE, sizeof(*dtev), M_DEVBUF,
+		    M_WAITOK|M_CANFAIL|M_ZERO);
 		if (dtev == NULL)
 			break;
 		sc->ds_cpu[i].dc_ring = dtev;
@@ -375,6 +369,12 @@ dtalloc(void)
 		return NULL;
 	}
 
+	sc->ds_si = softintr_establish(IPL_SOFTCLOCK, dt_deferred_wakeup, sc);
+	if (sc->ds_si == NULL) {
+		dtfree(sc);
+		return NULL;
+	}
+
 	return sc;
 }
 
@@ -384,10 +384,12 @@ dtfree(struct dt_softc *sc)
 	struct dt_evt *dtev;
 	int i;
 
+	if (sc->ds_si != NULL)
+		softintr_disestablish(sc->ds_si);
+
 	for (i = 0; i < ncpusfound; i++) {
 		dtev = sc->ds_cpu[i].dc_ring;
-		if (dtev != NULL)
-			free(dtev, M_DT, DT_EVTRING_SIZE * sizeof(*dtev));
+		free(dtev, M_DEVBUF, DT_EVTRING_SIZE * sizeof(*dtev));
 	}
 	free(sc, M_DEVBUF, sizeof(*sc));
 }