/* device structure: *  This structure defines the basic information needed for device *  control.  The table of devices is initialized at compile time *  with each device assigned an integer device descriptor. */struct device {    int     (*init)(unsigned long);    int     (*ctrl)(int,unsigned long,unsigned long);    int     (*open)(unsigned long,unsigned long);    int     (*close)();    int     (*read)(char *,int);    int     (*write)(char *,int);    char    *name;};extern struct device    devtbl[];/* Generic driver functions: */extern  int open(int, unsigned long, unsigned long);extern  int close(int);extern  int read(int, char *, int);extern  int write(int, char *, int);extern  int init(int, unsigned long);extern  int ioctl(int, int, unsigned long, unsigned long);extern  int devInit(int);extern  int isbaddev(int);extern  void devtbldump(void);/* Common ioctl definitions: */#define INIT        1#define GOTACHAR    2#define SETBAUD     3#define nodriver    0extern int ConsoleDevice;