int s2io_close (struct net_device * dev);
This is the stop entry point of the driver. It needs to undo exactly whatever was done by the open entry point,thus it's usually referred to as the close function.Among other things this function mainly stops the Rx side of the NIC and frees all the Rx buffers in the Rx rings.
0 on success and an appropriate (-)ve integer as defined in errno.h file on failure.