[root@devel3 root]# grep "#define _IOR" `locate ioctl.h`

/usr/include/asm/ioctl.h:#define _IOR(type,nr,size)     _IOC(_IOC_READ,(type),(nr),sizeof(size))
/usr/src/linux-2.4.18-3/include/asm-i386/ioctl.h:#define _IOR(type,nr,size)     _IOC(_IOC_READ,(type),(nr),sizeof(size))
/usr/src/linux-2.4.18-27.7.x/include/asm-i386/ioctl.h:#define _IOR(type,nr,size)        _IOC(_IOC_READ,(type),(nr),sizeof(size))
/usr/i386-glibc21-linux/include/asm/ioctl.h:#define _IOR(type,nr,size)  _IOC(_IOC_READ,(type),(nr),sizeof(size))
[root@devel3 root]#