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ioctl

macros to define the commands

  • _IO(type, nr): request takes no argument;
  • _IOR(type, nr, datatype): request reads data from the kernel;
  • _IOW(type, nr, datatype): request writes data to the kernel;
  • _IOWR(type, nr, datatype): request reads data from and writes data to the kernel.

some examples

#define TM_MAGIC	'N'
#define TM_GET		_IOR(TM_MAGIC, 20, struct task_sample_usr)
#define TM_STOP		_IO(TM_MAGIC, 21)
#define TM_START	_IO(TM_MAGIC, 22)
#define TM_PID		_IOWR(TM_MAGIC, 23, __s64)