vcan_ioctl_cmd
==============

Here is the definition::

  typedef enum
    { VCAN_IOCTL_CAN=0,
      VCAN_IOCTL_SETNAME=1,
      VCAN_IOCTL_IDENTIFY=2,
      VCAN_IOCTL_VERSION=3
    } vcan_ioctl_cmd;

This is the data type for all ioctl-commands that can be performed
by the driver. The 'command' parameter of the ``ioctl``-function
has to have a value according to ``vcan_ioctl_cmd``. The driver-function
is selected according to the value of that 'command' parameter.

VCAN_IOCTL_CAN
  This constant specifies that a CAN-status function is to be performed. See
  also ``vcan_status_tag``.

VCAN_IOCTL_SETNAME
  This constant is used to call the set-name function of the driver. A name
  is assigned to the thread that calls this function. If the thread later
  crashed without closing the driver, that name can be used to get the
  appropriate file-handle to the driver back. The name is a string that is
  given to the ioctl-function as data-pointer.

VCAN_IOCTL_IDENTIFY
  This constant is used to call the identify- function of the driver. The
  driver looks up it's internal list of thread-names and assigns the
  file-handle to the objects that are or were used by the thread that was
  registered with that name. The name is a string that is given to the
  ioctl-function as data-pointer.

VCAN_IOCTL_VERSION
  This constant is used to call the version- function of the driver. The
  major- and minor version numbers are returned in the data-field of the
  ioctl-function. This data-field is always a pointer, to the address
  'pointer' and 'pointer+1' the driver's major version number is written as
  a short-integer. The driver's minor version number is written to
  'pointer+2' and 'pointer+3' as a short-integer.