diff --git a/include/lib/io_storage.h b/include/lib/io_storage.h
index b6c5f9f..ae1158c 100644
--- a/include/lib/io_storage.h
+++ b/include/lib/io_storage.h
@@ -31,6 +31,7 @@
 #ifndef __IO_H__
 #define __IO_H__
 
+#include <stdint.h>
 #include <stdio.h> /* For ssize_t */
 
 
@@ -58,13 +59,6 @@
 /* Connector type, providing a means of identifying a device to open */
 struct io_dev_connector;
 
-/* Device handle, providing a client with access to a specific device */
-typedef struct io_dev_info *io_dev_handle;
-
-/* IO handle, providing a client with access to a specific source of data from
- * a device */
-typedef struct io_entity *io_handle;
-
 
 /* File specification - used to refer to data on a device supporting file-like
  * entities */
@@ -77,7 +71,7 @@
 /* Block specification - used to refer to data on a device supporting
  * block-like entities */
 typedef struct io_block_spec {
-	unsigned long offset;
+	size_t offset;
 	size_t length;
 } io_block_spec_t;
 
@@ -96,33 +90,35 @@
 
 
 /* Open a connection to a device */
-int io_dev_open(struct io_dev_connector *dev_con, void *dev_spec,
-		io_dev_handle *dev_handle);
+int io_dev_open(const struct io_dev_connector *dev_con,
+		const uintptr_t dev_spec,
+		uintptr_t *dev_handle);
 
 
 /* Initialise a device explicitly - to permit lazy initialisation or
  * re-initialisation */
-int io_dev_init(io_dev_handle dev_handle, const void *init_params);
+int io_dev_init(uintptr_t dev_handle, const uintptr_t init_params);
 
 /* TODO: Consider whether an explicit "shutdown" API should be included */
 
 /* Close a connection to a device */
-int io_dev_close(io_dev_handle dev_handle);
+int io_dev_close(uintptr_t dev_handle);
 
 
 /* Synchronous operations */
-int io_open(io_dev_handle dev_handle, const void *spec, io_handle *handle);
+int io_open(uintptr_t dev_handle, const uintptr_t spec, uintptr_t *handle);
 
-int io_seek(io_handle handle, io_seek_mode_t mode, ssize_t offset);
+int io_seek(uintptr_t handle, io_seek_mode_t mode, ssize_t offset);
 
-int io_size(io_handle handle, size_t *length);
+int io_size(uintptr_t handle, size_t *length);
 
-int io_read(io_handle handle, void *buffer, size_t length, size_t *length_read);
+int io_read(uintptr_t handle, uintptr_t buffer, size_t length,
+		size_t *length_read);
 
-int io_write(io_handle handle, const void *buffer, size_t length,
+int io_write(uintptr_t handle, const uintptr_t buffer, size_t length,
 		size_t *length_written);
 
-int io_close(io_handle handle);
+int io_close(uintptr_t handle);
 
 
 #endif /* __IO_H__ */
diff --git a/include/lib/semihosting.h b/include/lib/semihosting.h
index 9d0b39f..b4eecc5 100644
--- a/include/lib/semihosting.h
+++ b/include/lib/semihosting.h
@@ -31,6 +31,7 @@
 #ifndef __SEMIHOSTING_H__
 #define __SEMIHOSTING_H__
 
+#include <stdint.h>
 #include <stdio.h> /* For ssize_t */
 
 
@@ -63,17 +64,17 @@
 long semihosting_connection_supported(void);
 long semihosting_file_open(const char *file_name, size_t mode);
 long semihosting_file_seek(long file_handle, ssize_t offset);
-long semihosting_file_read(long file_handle, size_t *length, void *buffer);
+long semihosting_file_read(long file_handle, size_t *length, uintptr_t buffer);
 long semihosting_file_write(long file_handle,
 			    size_t *length,
-			    const void *buffer);
+			    const uintptr_t buffer);
 long semihosting_file_close(long file_handle);
 long semihosting_file_length(long file_handle);
 long semihosting_system(char *command_line);
 long semihosting_get_flen(const char *file_name);
 long semihosting_download_file(const char *file_name,
 			       size_t buf_size,
-			       void *buf);
+			       uintptr_t buf);
 void semihosting_write_char(char character);
 void semihosting_write_string(char *string);
 char semihosting_read_char(void);