Index: sys/kern/subr_bus.c
===================================================================
--- sys/kern/subr_bus.c
+++ sys/kern/subr_bus.c
@@ -878,6 +878,30 @@
 	}
 }
 
+/**
+ * @brief safely quotes strings that might have double quotes in them.
+ *
+ * The devctl protocol relies on quoted strings having matching quotes.
+ * This routine quotes any internal quotes so the resulting string
+ * is safe to pass to snprintf to construct, for example pnp info strings.
+ *
+ * @param sb	sbuf to place the characters into
+ * @param src	Original buffer.
+ * @param len	Max length of the buffer to process.
+ */
+void
+devctl_safe_quote_sb_len(struct sbuf *sb, const char *src, size_t len)
+{
+	const char *srcp;
+
+	srcp = src;
+	while (*srcp != '\0' && (srcp - src) < len) {
+		if (*srcp == '"' || *srcp == '\\')
+			sbuf_putc(sb, '\\');
+		sbuf_putc(sb, *srcp++);
+	}
+}
+
 /* End of /dev/devctl code */
 
 static struct device_list bus_data_devices;
Index: sys/sys/devctl.h
===================================================================
--- sys/sys/devctl.h
+++ sys/sys/devctl.h
@@ -19,6 +19,7 @@
     const char *__type, const char *__data);
 struct sbuf;
 void devctl_safe_quote_sb(struct sbuf *__sb, const char *__src);
+void devctl_safe_quote_sb_len(struct sbuf *sb, const char *src, size_t len);
 #endif
 
 #endif /* _SYS_DEVCTL_H_ */