13df2l5.txt
;**************************************************************************************************
; LISTING 5 - IOCTL () ROUTINE
;
; "Get those boards talking under Linux," EDN, June 22, 2000, pg 153
;
; http://www.ednmag.com/ednmag/reg/2000/06222000/13df2.htm
;****************************************************************************************************

static int pd_ioctl( . . . )
{
    int real_minor, board, board_minor;
    // Find out which board/subsystem ioctl is going to access
    real_minor = MINOR(file->f_dentry->d_inode->i_rdev);
    board = real_minor / PD_MINOR_RANGE;
    board_minor = real_minor % PD_MINOR_RANGE;
    // check board subsystem ownership, does it belong to calling process?
    if (!pd_CheckOwnerPID(board, board_minor, current->pid)) return -EBUSY; 
    // call registered dispatch routine
    iRes = pIoctlProc[board](board, board_minor, ... );
... 
}