serial: Add Darwin/macOS support for custom and >230400 baudrates

This change is based on the patch proposed by Denis Ahrens in
https://review.coreboot.org/c/flashrom/+/67822

Change-Id: I3e6b88d2b4c2a130b16456752681fd9f807bf6f0
Signed-off-by: Peter Stuge <peter@stuge.se>
Original-Reviewed-on: https://review.coreboot.org/c/flashrom/+/70571
Original-Reviewed-by: Thomas Heijligen <src@posteo.de>
Reviewed-on: https://review.coreboot.org/c/flashrom-stable/+/73480
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
diff --git a/custom_baud_darwin.c b/custom_baud_darwin.c
new file mode 100644
index 0000000..e8764dd
--- /dev/null
+++ b/custom_baud_darwin.c
@@ -0,0 +1,61 @@
+/*
+ * This file is part of the flashrom project.
+ *
+ * Copyright (C) 2022 Peter Stuge <peter@stuge.se>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <termios.h>
+#include <sys/ioctl.h>
+#include <IOKit/serial/ioss.h>
+#include <errno.h>
+
+#include "custom_baud.h"
+
+int use_custom_baud(unsigned int baud, const struct baudentry *baudtable)
+{
+	int i;
+
+	if (baud > 230400)
+		return 1;
+
+	for (i = 0; baudtable[i].baud; i++) {
+		if (baudtable[i].baud == baud)
+			return 0;
+
+		if (baudtable[i].baud > baud)
+			return 1;
+	}
+
+	return 1;
+}
+
+int set_custom_baudrate(int fd, unsigned int baud, const enum custom_baud_stage stage, void *tio_wanted)
+{
+	struct termios *wanted;
+	speed_t speed;
+
+	switch (stage) {
+	case BEFORE_FLAGS:
+		break;
+
+	case WITH_FLAGS:
+		wanted = tio_wanted;
+		return cfsetspeed(wanted, B19200);
+
+	case AFTER_FLAGS:
+		speed = baud;
+		return ioctl(fd, IOSSIOSPEED, &speed);
+	}
+
+	return 0;
+}