diff --git a/hwaccess_x86_io.c b/hwaccess_x86_io.c
index fc6ee54..37b1eb7 100644
--- a/hwaccess_x86_io.c
+++ b/hwaccess_x86_io.c
@@ -2,6 +2,8 @@
  * This file is part of the flashrom project.
  *
  * Copyright (C) 2009,2010 Carl-Daniel Hailfinger
+ * Copyright (C) 2022 secunet Security Networks AG
+ * (Written by Thomas Heijligen <thomas.heijligen@secunet.com)
  *
  * 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
@@ -14,73 +16,121 @@
  * GNU General Public License for more details.
  */
 
+/*
+ * This file implements x86 I/O port permission handling.
+ *
+ * For this purpose the platform specific code is encapsuled in two functions
+ * and compiled only on the respective platform. `platform_get_io_perms()` is
+ * called to get the permissions and `platform_release_io_perms()` is called for
+ * releasing those.
+ */
+
 #include <errno.h>
 #include <string.h>
-#if !defined (__DJGPP__) && !defined(__LIBPAYLOAD__)
-/* No file access needed/possible to get hardware access permissions. */
-#include <unistd.h>
-#include <fcntl.h>
-#endif
 
-#include "hwaccess_x86_io.h"
 #include "flash.h"
+#include "hwaccess_x86_io.h"
 
-#if USE_IOPERM
-#include <sys/io.h>
-#endif
-
-#if USE_DEV_IO
-int io_fd;
-#endif
-
-#if !(defined(__DJGPP__) || defined(__LIBPAYLOAD__))
-static int release_io_perms(void *p)
+#if defined(__DJGPP__) || defined(__LIBPAYLOAD) /* DJGPP, libpayload */
+static int platform_get_io_perms(void)
 {
-#if defined (__sun)
+	return 0;
+}
+
+static int platform_release_io_perms(void *p)
+{
+	return 0;
+}
+#endif
+
+#if defined(__sun) /* SunOS */
+#include <sys/sysi86.h>
+
+static int platform_get_io_perms(void)
+{
+	return sysi86(SI86V86, V86SC_IOPL, PS_IOPL);
+}
+
+static int platform_release_io_perms(void *p)
+{
 	sysi86(SI86V86, V86SC_IOPL, 0);
-#elif USE_DEV_IO
+	return 0;
+}
+#endif
+
+#if USE_DEV_IO /* FreeBSD, DragonFlyBSD */
+#include <fcntl.h>
+#include <unistd.h>
+
+int io_fd;
+
+static int platform_get_io_perms(void)
+{
+	io_fd = open("/dev/io", O_RDWR);
+	return (io_fd >= 0 ? 0 : -1);
+}
+
+static int platform_release_io_perms(void *p)
+{
 	close(io_fd);
-#elif USE_IOPERM
+	return 0;
+}
+#endif
+
+#if USE_IOPERM /* GNU Hurd */
+#include <sys/io.h>
+
+static int platform_get_io_perms(void)
+{
+	return ioperm(0, 65536, 1);
+}
+
+static int platform_release_io_perms(void *p)
+{
 	ioperm(0, 65536, 0);
-#elif USE_IOPL
+	return 0;
+}
+#endif
+
+#if USE_IOPL /* Linux, Darwin, NetBSD, OpenBSD */
+static int platform_get_io_perms(void)
+{
+	return iopl(3);
+}
+
+static int platform_release_io_perms(void *p)
+{
 	iopl(0);
-#endif
 	return 0;
 }
+#endif
 
-/* Get I/O permissions with automatic permission release on shutdown. */
+/**
+ * @brief Get access to the x86 I/O ports
+ *
+ * This function abstracts the platform dependent function to get access to the
+ * x86 I/O ports and musst be called before using IN[B/W/L] or OUT[B/W/L].
+ * It registers a shutdown function to release those privileges.
+ *
+ * @return 0 on success, platform specific number on failure
+ */
 int rget_io_perms(void)
 {
-	#if defined (__sun)
-	if (sysi86(SI86V86, V86SC_IOPL, PS_IOPL) != 0) {
-#elif USE_DEV_IO
-	if ((io_fd = open("/dev/io", O_RDWR)) < 0) {
-#elif USE_IOPERM
-	if (ioperm(0, 65536, 1) != 0) {
-#elif USE_IOPL
-	if (iopl(3) != 0) {
-#endif
-		msg_perr("ERROR: Could not get I/O privileges (%s).\n", strerror(errno));
-		msg_perr("You need to be root.\n");
-#if defined (__OpenBSD__)
-		msg_perr("If you are root already please set securelevel=-1 in /etc/rc.securelevel and\n"
-			 "reboot, or reboot into single user mode.\n");
-#elif defined(__NetBSD__)
-		msg_perr("If you are root already please reboot into single user mode or make sure\n"
-			 "that your kernel configuration has the option INSECURE enabled.\n");
-#endif
-		return 1;
-	} else {
-		register_shutdown(release_io_perms, NULL);
+	if (platform_get_io_perms() == 0) {
+		register_shutdown(platform_release_io_perms, NULL);
+		return 0;
 	}
-	return 0;
-}
-
+	msg_perr("ERROR: Could not get I/O privileges (%s).\n", strerror(errno));
+	msg_perr("Make sure you are root.\n");
+#if defined (__OpenBSD__)
+	msg_perr("If you are root already please set securelevel=-1 in /etc/rc.securelevel and\n"
+		 "reboot, or reboot into single user mode.\n");
+#elif defined(__NetBSD__)
+	msg_perr("If you are root already please reboot into single user mode or make sure\n"
+		 "that your kernel configuration has the option INSECURE enabled.\n");
 #else
-
-/* DJGPP and libpayload environments have full PCI port I/O permissions by default. */
-int rget_io_perms(void)
-{
-	return 0;
-}
+	msg_perr("If you are root, your kernel may still prevent access based on\n"
+		 "security policies.\n");
 #endif
+	return 1;
+}