This chapter introduced the following symbols and header
files. The list of the fields in struct file_operations and
struct file is not repeated here.
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#include <linux/fs.h> The ``File System'' header is the header required for writing device drivers. All the important functions are declared in here.
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int register_chrdev(unsigned int major, const char *name,,struct file_operations *fops); Registers a character device driver. If the major number is not zero, it is used unchanged; if the number is zero, then a dynamic number is assigned for this device.
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int unregister_chrdev(unsigned int major, const char *name); Deregisters the driver at unload time. Both
majorand thenamestring must contain the same values that were used to register the driver.-
kdev_t inode->i_rdev; The device ``number'' for the current device is accessible from the
inodeargument passed to every device method.-
int MAJOR(kdev_t dev);,int MINOR(kdev_t dev); These macros extract the major and minor numbers from a device item.
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kdev_t MKDEV(int major, int minor); This macro builds a
kdev_tdata item from the major and minor numbers.-
#include <asm/segment.h> This header defines functions related to cross-space copying in all kernels up to and including 2.0. The functions are the ones used to copy data from the user segment to the kernel segment and vice versa. Version 2.1 changed the header’s name as well as the functions (see Section 17.3 in Chapter 17 for more information).
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void memcpy_fromfs(void *to, const void *from,,unsigned long count);,void memcpy_tofs(void *to, const void *from,,unsigned long count); These functions are used to copy an array of bytes from user space to kernel space and vice versa. ``FS'' is the i386 segment register used to address user space from kernel code. These functions changed in 2.1.