Since you people think me to be a newbie or moron or some thing like copy pasting the code so I am explaining each and every line of it what it is doing but still lectures are lectures and funda's don't work show me real thing or else do not reply.
#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h> /* printk() */
#include <linux/slab.h> /* kmalloc() */
#include <linux/fs.h> /* everything... */
#include <linux/errno.h> /* error codes */
#include <linux/types.h> /* size_t */
#include <linux/proc_fs.h>
#include <linux/fcntl.h> /* O_ACCMODE */
#include <asm/system.h> /* cli(), *_flags */
#include <asm/uaccess.h> /* copy_from/to_user */
The section declared above is used to include header files.
MODULE_LICENSE("Dual BSD/GPL");
MODULE_LICENSE is an exported symbol.
int bond_open(struct inode *inode, struct file *filp);
int bond_release(struct inode *inode, struct file *filp);
ssize_t bond_read(struct file *filp, char *buf, size_t count, loff_t *f_pos);
ssize_t bond_write(struct file *filp, char *buf, size_t count, loff_t *f_pos);
just above defined four functions which will be used in structure file_operations which is of type defined in fs.h
void bond_exit(void);
int bond_init(void);
my init and exit modules of code.
struct file_operations bond_fops = {
.read = bond_read,
.write = bond_write,
.open = bond_open,
.release = bond_release
declared as above as per new C99 rules so that rest of the file_operations which are not defined be declared NULL
};
above operations corresponding to the system calls an application can apply to a file : file operations as in fs.h
module_init(bond_init);
module_exit(bond_exit);
my init and exit modules
int bond_major = 60;
there is another way alloc_chrdrv but I am using register_chrdrv so defining the major number
char *bond_buffer;
device buffer to store data when user programs access it
int bond_init(void) {
int result;
result = register_chrdev(bond_major, "bond", &bond_fops);
if (result < 0) {
printk(KERN_ALERT "memory: cannot obtain major number %d\n", bond_major);
return result;
}
bond_buffer = kmalloc(14, GFP_KERNEL);
giving 14 bytes to buffer three types GFP_KERNEL,GFP_ATOMIC one more I forgot
if (!bond_buffer) {
result = -ENOMEM;
goto fail;
}
in case of error above will stop execution
memset(bond_buffer, 0, 14);
filling all the bytes of memory Claros pointed me here that if I ever used malloc function in my life so mentioning this was important for him.
printk(KERN_ALERT "Inserting bond module\n");
return 0;
fail:
bond_exit();
return result;
same when returns a -ve value if fail to register the major number 60
}
void bond_exit(void) {
unregister_chrdev(bond_major, "bond");
if (bond_buffer) {
kfree(bond_buffer);
}
printk( KERN_ALERT "Removing bond module\n");
}
just above is a clean up module when driver exits or unloads
int bond_open(struct inode *inode, struct file *filp) {
return 0;
}
will be needed when a process opens the file
int bond_release(struct inode *inode, struct file *filp) {
return 0;
}
when releasing device driver
ssize_t bond_read(struct file *filp, char *buf,
size_t count, loff_t *f_pos) {
copy_to_user(buf,bond_buffer,count<14 ? count:14);
This function works as given here
http://www.gnugeneration.com/mirrors/kernel-api/r4299.html
and an example of this in the current kernel is linux-2.6/drivers/char/snsc.c
they implemented a function scdrv_write I implemented bond_write both implementations are different
do you people get that or still some lecture is missing.
}
ssize_t bond_write( struct file *filp, char *buf,
size_t count, loff_t *f_pos) {
copy_from_user(bond_buffer,buf,count<14 ? count : 14);
from the userspace buf copy the bytes whose total number is equal to count to bond_buffer
return 1;
}
The above fundas and lectures do not work.You people give lectures or show attitude but only if the code works.
