__inout_bcount
__inout_bcount(partn_size) caddr_t partn_data,
__inout_bcount(max_seg_size) caddr_t seg_data,
__inout_bcount(size) caddr_t data,
__inout_bcount(size) caddr_t data,
__inout_bcount(size) caddr_t data,
__inout_bcount(size) caddr_t data,