NAME
        TD_ADDCHANGEINT -- add a disk change software interrupt handler.

   FUNCTION
        This command lets you add a software interrupt handler to the
        disk device that gets invoked whenever a disk insertion or removal
        occurs.

        You must pass in a properly initialized Exec interrupt structure
        and be prepared to deal with disk insertions/removals
        immediately. From within the interrupt handler, you may only call the
        status commands that can use IOF_QUICK.

        To set up the handler, an interrupt structure must be initialized.
        This structure is supplied as the io_Data to the TD_ADDCHANGEINT
        command. The handler then gets linked into the handler chain and
        gets invoked whenever a disk change happens. You must eventually
        remove the handler before you exit.

        This command only returns when the handler is removed. That is,
        the device holds onto the IO request until the td_remchangeint command
        is executed with that same IO request. Hence, you must use sendio()
        with this command.

   IO REQUEST INPUT
        io_Device       preset by the call to opendevice()
        io_Unit         preset by the call to opendevice()
        io_Command      TD_ADDCHANGEINT
        io_Flags        0
        io_Length       sizeof(struct Interrupt)
        io_Data         pointer to interrupt structure

   IO REQUEST RESULT
        io_Error - 0 for success, or an error code as defined in
                   <devices/trackdisk.h>

   SEE ALSO
        td_remchangeint, <devices/trackdisk.h>, <exec/interrupts.h>,
        exec.library/cause()