diff --git a/drivers/io/io_memmap.c b/drivers/io/io_memmap.c
index 96590b6..eed50cc 100644
--- a/drivers/io/io_memmap.c
+++ b/drivers/io/io_memmap.c
@@ -23,10 +23,10 @@
 	/* Use the 'in_use' flag as any value for base and file_pos could be
 	 * valid.
 	 */
-	int		in_use;
-	uintptr_t	base;
-	size_t		file_pos;
-	size_t		size;
+	int			in_use;
+	uintptr_t		base;
+	unsigned long long	file_pos;
+	unsigned long long	size;
 } file_state_t;
 
 static file_state_t current_file = {0};
@@ -42,7 +42,7 @@
 static int memmap_block_open(io_dev_info_t *dev_info, const uintptr_t spec,
 			     io_entity_t *entity);
 static int memmap_block_seek(io_entity_t *entity, int mode,
-			     ssize_t offset);
+			     signed long long offset);
 static int memmap_block_len(io_entity_t *entity, size_t *length);
 static int memmap_block_read(io_entity_t *entity, uintptr_t buffer,
 			     size_t length, size_t *length_read);
@@ -129,7 +129,8 @@
 
 
 /* Seek to a particular file offset on the memmap device */
-static int memmap_block_seek(io_entity_t *entity, int mode, ssize_t offset)
+static int memmap_block_seek(io_entity_t *entity, int mode,
+			     signed long long offset)
 {
 	int result = -ENOENT;
 	file_state_t *fp;
@@ -141,10 +142,11 @@
 		fp = (file_state_t *) entity->info;
 
 		/* Assert that new file position is valid */
-		assert((offset >= 0) && (offset < fp->size));
+		assert((offset >= 0) &&
+		       ((unsigned long long)offset < fp->size));
 
 		/* Reset file position */
-		fp->file_pos = offset;
+		fp->file_pos = (unsigned long long)offset;
 		result = 0;
 	}
 
@@ -158,7 +160,7 @@
 	assert(entity != NULL);
 	assert(length != NULL);
 
-	*length = ((file_state_t *)entity->info)->size;
+	*length = (size_t)((file_state_t *)entity->info)->size;
 
 	return 0;
 }
@@ -169,7 +171,7 @@
 			     size_t length, size_t *length_read)
 {
 	file_state_t *fp;
-	size_t pos_after;
+	unsigned long long pos_after;
 
 	assert(entity != NULL);
 	assert(length_read != NULL);
@@ -180,7 +182,8 @@
 	pos_after = fp->file_pos + length;
 	assert((pos_after >= fp->file_pos) && (pos_after <= fp->size));
 
-	memcpy((void *)buffer, (void *)(fp->base + fp->file_pos), length);
+	memcpy((void *)buffer,
+	       (void *)((uintptr_t)(fp->base + fp->file_pos)), length);
 
 	*length_read = length;
 
@@ -196,7 +199,7 @@
 			      size_t length, size_t *length_written)
 {
 	file_state_t *fp;
-	size_t pos_after;
+	unsigned long long pos_after;
 
 	assert(entity != NULL);
 	assert(length_written != NULL);
@@ -207,7 +210,8 @@
 	pos_after = fp->file_pos + length;
 	assert((pos_after >= fp->file_pos) && (pos_after <= fp->size));
 
-	memcpy((void *)(fp->base + fp->file_pos), (void *)buffer, length);
+	memcpy((void *)((uintptr_t)(fp->base + fp->file_pos)),
+	       (void *)buffer, length);
 
 	*length_written = length;