diff --git a/hwaccess.h b/hwaccess.h
index eea3652..c10b12e 100644
--- a/hwaccess.h
+++ b/hwaccess.h
@@ -68,6 +68,13 @@
 #error Little-endian PowerPC #defines are unknown
 #endif
 
+#elif defined (__arm__)
+#if defined (__ARMEL__)
+#define __FLASHROM_LITTLE_ENDIAN__ 1
+#else
+#error Big-endian ARM #defines are unknown
+#endif
+
 #endif
 
 #if !defined (__FLASHROM_BIG_ENDIAN__) && !defined (__FLASHROM_LITTLE_ENDIAN__)
@@ -326,6 +333,10 @@
 
 /* PCI port I/O is not yet implemented on MIPS. */
 
+#elif defined(__arm__)
+
+/* Non memory mapped I/O is not supported on ARM. */
+
 #else
 
 #error Unknown architecture, please check if it supports PCI port IO.