diff --git a/include/socks/device.h b/include/socks/device.h
index 2cb76c8..c4cdb8c 100644
--- a/include/socks/device.h
+++ b/include/socks/device.h
@@ -43,6 +43,11 @@ enum device_type {
 	DEV_TYPE_FRAMEBUFFER,
 };
 
+struct iovec {
+	void *io_buf;
+	size_t io_len;
+};
+
 struct device_type_ops {
 	kern_status_t(*read)(struct device *, void *, size_t, size_t *, socks_flags_t);
 	kern_status_t(*write)(struct device *, const void *, size_t, size_t *, socks_flags_t);
@@ -50,8 +55,8 @@ struct device_type_ops {
 };
 
 struct block_device_ops {
-	kern_status_t(*read_blocks)(struct device *, void *, size_t, size_t *, socks_flags_t);
-	kern_status_t(*write_blocks)(struct device *, const void *, size_t, size_t *, socks_flags_t);
+	kern_status_t(*read_blocks)(struct device *, sectors_t, size_t, struct iovec *, size_t, socks_flags_t);
+	kern_status_t(*write_blocks)(struct device *, sectors_t, size_t, struct iovec *, size_t, socks_flags_t);
 	kern_status_t(*ioctl)(struct device *, unsigned int, void *);
 };
 
@@ -165,11 +170,6 @@ struct driver {
 	struct driver_ops *drv_ops;
 };
 
-struct iovec {
-	void *io_buf;
-	size_t io_len;
-};
-
 extern kern_status_t device_init(void);
 extern struct device *root_device(void);
 extern struct device *misc_device(void);