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_IOWR(9r)
NAME
  _IOWR - General: Defines ioctl types for device control operations

SYNOPSIS
  #include <sys/ioctl.h>


  _IOWR(
	  g,
	  n,
	  t );

ARGUMENTS
  g   Specifies the group that this ioctl type belongs to. This argument must
      be a nonnegative 8-bit number (that is, in the range 0-255 inclusive).
      You can pass the value zero (0) to this argument if a new ioctl group
      is not being defined.

  n   Specifies the specific ioctl type within the group. These types should
      be sequentially assigned numbers for each different ioctl operation the
      driver supports. This argument must be a nonnegative 8-bit number (that
      is, in the range 0-255 inclusive).

  t   Specifies the size of the data passed from the user application back to
      the kernel. The kernel determines the number of bytes to transfer by
      passing the value in this argument to the sizeof operator.  Upon
      completion of the ioctl operation, this same data structure contains
      the data returned from the driver back to the user level application.

DESCRIPTION
  The _IOWR macro defines ioctl types for situations where data is
  transferred from the user's buffer into the kernel. The driver then
  performs the appropriate ioctl operation and returns data of the same size
  back up to the user-level application.  Typically, this data consists of
  device control or status information passed to the driver from the
  application program.

EXAMPLE
  The following example uses the _IOWR macro to construct an ioctl called
  DN_SETVERIFY. Note that DN_SETVERIFY passes the value zero (0) for the
  group that this ioctl belongs to and the value 4 to identify the specific
  ioctl type within the group. The DN_SETVERIFY ioctl also passes the data
  type int, which the kernel passes to the sizeof operator  to determine how
  much data is passed from the user application back to the kernel.

       #define DN_SETVERIFY    _IOWR(0,4,int)









SEE ALSO
  ioctl Commands: _IO(9r), _IOR(9r), _IOW(9r)

Index for Section 9

Alphabetical listing for Special Characters

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