ioc_read_subchannel_buf
struct ioc_read_subchannel_buf tt_subchannel;
&((struct ioc_read_subchannel_buf *)addr)->info);
struct ioc_read_subchannel_buf *args = addr;
#define CDIOCREADSUBCHANNEL_BUF _IOWR('c', 3, struct ioc_read_subchannel_buf)