Linux Device Drivers Development

File representation in the kernel

The kernel describes files as instances of the struct inode (not struct file) structure, defined in include/linux/fs.h:

struct inode { 
    [...] 
   struct pipe_inode_info *i_pipe;     /* Set and used if this is a 
 *linux kernel pipe */ 
   struct block_device *i_bdev;  /* Set and used if this is a 
 * a block device */ 
   struct cdev       *i_cdev;    /* Set and used if this is a 
 * character device */ 
    [...] 
} 

struct inode is a filesystem data structure holding information, which is only relevant to the OS, about a file (its type, character, block, pipe, and so on) or directory (yes!! from a kernel point of view, a directory is a file that on entry points to other files) on disk.

The struct file structure (also defined in include/linux/fs.h ...