taglinefilesource code
_IOW38include/linux/ioctl.h#define _IOW(c,d,t)  (IOC_IN | ((sizeof(t)<<16) & IOCSIZE_MASK) | \
_IOW77include/linux/soundcard.h#define  _IOW(x,y,t)  ((int)(IOC_IN|((sizeof(t)&IOCPARM_MASK)<<16)|(x<<8)|y))