diff --git a/share/man/man9/Makefile b/share/man/man9/Makefile
--- a/share/man/man9/Makefile
+++ b/share/man/man9/Makefile
@@ -1028,6 +1028,7 @@
 MLINKS+=dev_clone.9 drain_dev_clone_events.9
 MLINKS+=dev_refthread.9 devvn_refthread.9 \
 	dev_refthread.9 dev_relthread.9
+MLINKS+=devctl_notify.9 devctl_notifyf.9
 MLINKS+=devfs_set_cdevpriv.9 devfs_clear_cdevpriv.9 \
 	devfs_set_cdevpriv.9 devfs_get_cdevpriv.9 \
 	devfs_set_cdevpriv.9 devfs_foreach_cdevpriv.9
diff --git a/share/man/man9/devctl_notify.9 b/share/man/man9/devctl_notify.9
--- a/share/man/man9/devctl_notify.9
+++ b/share/man/man9/devctl_notify.9
@@ -21,16 +21,19 @@
 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd September 22, 2020
+.Dd April 21, 2025
 .Dt DEVCTL_NOTIFY 9
 .Os
 .Sh NAME
-.Nm devctl_notify
+.Nm devctl_notify ,
+.Nm devctl_notifyf
 .Nd Send a message, via devctl, to userland
 .Sh SYNOPSIS
 .In sys/devctl.h
 .Ft void
 .Fn devctl_notify "const char *system" "const char *subsystem" "const char *type" "const char *data"
+.Ft void
+.Fn devctl_notifyf "const char *system" "const char *subsystem" "const char *type" "const char *datafmt" "..."
 .Sh DESCRIPTION
 Send a notification to user land via
 .Xr devctl 4 .
@@ -64,11 +67,22 @@
 discover itself and sending all the data userland will want to use to
 decide what to do with the message.
 .Pp
+The
+.Fn devctl_notifyf
+function is identical to
+.Fn devctl_notify ,
+except it takes a format string to populate
+.Fa data
+and formats it as
+.Xr printf 9
+would print it.
+.Pp
 The current total message length limit is just under 1kb.
 Senders should try to remain well below this limit.
 .Sh SEE ALSO
 .Xr devctl 4 ,
-.Xr devd 8
+.Xr devd 8 ,
+.Xr printf 9
 .Sh AUTHORS
 This manual page was written by
 .An M. Warner Losh
diff --git a/sys/kern/kern_devctl.c b/sys/kern/kern_devctl.c
--- a/sys/kern/kern_devctl.c
+++ b/sys/kern/kern_devctl.c
@@ -430,19 +430,20 @@
 }
 
 /**
- * @brief Send a 'notification' to userland, using standard ways
+ * @brief Send a 'notification' to userland, using standard ways.  This version
+ * takes a format string and varargs, which fits a number of consumers' slightly
+ * less trivial needs.
  */
 void
-devctl_notify(const char *system, const char *subsystem, const char *type,
-    const char *data)
+devctl_notifyf(const char *system, const char *subsystem, const char *type,
+    const char *datafmt, ...)
 {
 	struct dev_event_info *dei;
 	struct sbuf sb;
+	ssize_t metasz;
 
 	if (system == NULL || subsystem == NULL || type == NULL)
 		return;
-	if (devctl_notify_hook.send_f != NULL)
-		devctl_notify_hook.send_f(system, subsystem, type, data);
 	dei = devctl_alloc_dei_sb(&sb);
 	if (dei == NULL)
 		return;
@@ -452,15 +453,77 @@
 	sbuf_cat(&sb, subsystem);
 	sbuf_cat(&sb, " type=");
 	sbuf_cat(&sb, type);
-	if (data != NULL) {
+
+	metasz = sbuf_len(&sb);
+	if (datafmt != NULL && *datafmt != '\0') {
+		va_list ap;
+
+		va_start(ap, datafmt);
 		sbuf_putc(&sb, ' ');
-		sbuf_cat(&sb, data);
+		sbuf_vprintf(&sb, datafmt, ap);
+		va_end(ap);
 	}
+
 	sbuf_putc(&sb, '\n');
-	if (sbuf_finish(&sb) != 0)
+	if (sbuf_finish(&sb) != 0) {
 		devctl_free_dei(dei);	/* overflow -> drop it */
-	else
-		devctl_queue(dei);
+		return;
+	}
+
+	if (devctl_notify_hook.send_f != NULL) {
+		ssize_t datasz;
+		char *hdata, *nlpos;
+
+		MPASS(metasz > 0);	/* Implies we overflowed */
+
+		nlpos = NULL;
+		if (datafmt == NULL) {
+			hdata = NULL;
+		} else {
+			/*
+			 * Chop off the newline while we send it to the hook,
+			 * we'll restore it after.
+			 */
+			hdata = sbuf_data(&sb);
+			datasz = sbuf_len(&sb);
+			nlpos = &hdata[datasz - 1];
+
+			MPASS(hdata[metasz] == ' ');
+			MPASS(*nlpos == '\n');
+			*nlpos = '\0';
+
+
+			/*
+			 * The sbuf was laid out like: [metadata] data,
+			 * so we advance here past the space.
+			 */
+			hdata += metasz + 1;
+		}
+
+		devctl_notify_hook.send_f(system, subsystem, type, hdata);
+
+		/* Fix the devctl formatted string before we enqueue. */
+		if (nlpos != NULL) {
+			*nlpos = '\n';
+		}
+	}
+
+	devctl_queue(dei);
+}
+
+/**
+ * @brief Send a 'notification' to userland, using standard ways
+ */
+void
+devctl_notify(const char *system, const char *subsystem, const char *type,
+    const char *data)
+{
+
+	if (data != NULL) {
+		devctl_notifyf(system, subsystem, type, "%s", data);
+	} else {
+		devctl_notifyf(system, subsystem, type, NULL);
+	}
 }
 
 /*
diff --git a/sys/sys/devctl.h b/sys/sys/devctl.h
--- a/sys/sys/devctl.h
+++ b/sys/sys/devctl.h
@@ -14,6 +14,8 @@
  */
 
 bool devctl_process_running(void);
+void devctl_notifyf(const char *__system, const char *__subsystem,
+    const char *__type, const char *__datafmt, ...) __printflike(4, 5);
 void devctl_notify(const char *__system, const char *__subsystem,
     const char *__type, const char *__data);
 struct sbuf;