file.h

struct file {
  enum { FD_NONE, FD_PIPE, FD_INODE, FD_DEVICE } type;
  int ref;
  char readable;
  char writable;
  struct pipe *pipe;
  struct inode *ip;
  uint off;
  short major;
};

#define major(dev)  ((dev) >> 16 & 0xFFFF)
#define minor(dev)  ((dev) & 0xFFFF)
#define	mkdev(m,n)  ((uint)((m)<<16| (n)))

TIP

in-memory copy of an inode

struct inode {
  uint dev;
  uint inum;
  int ref;
  struct sleeplock lock;
  int valid;

  short type;
  short major;
  short minor;
  short nlink;
  uint size;
  uint addrs[NDIRECT+1];
};

TIP

map major device number to device functions.

struct devsw {
  int (*read)(int, uint64, int);
  int (*write)(int, uint64, int);
};

extern struct devsw devsw[];

#define CONSOLE 1