1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
|
// Jack Sangdahl
// CSCI3753 SP24
// PA3 Device Driver
#include <linux/fs.h>
#include <linux/module.h>
#include <linux/slab.h>
MODULE_AUTHOR("jasa7131");
MODULE_LICENSE("GPL");
#define BUFFER_SIZE 900
#define MAJOR_NUM 510
#define DEVICE_NAME "char_dev"
static int major, counter = 0;
static char *data;
int char_driver_open(struct inode *, struct file *);
int char_driver_close(struct inode *, struct file *);
ssize_t char_driver_read(struct file *, char *, size_t, loff_t *);
ssize_t char_driver_write(struct file *, const char *, size_t, loff_t *);
loff_t char_driver_seek(struct file *, loff_t, int);
struct file_operations char_fops = {.owner = THIS_MODULE,
.open = char_driver_open,
.release = char_driver_close,
.read = char_driver_read,
.write = char_driver_write,
.llseek = char_driver_seek};
int char_driver_open(struct inode *pinode, struct file *pfile) {
counter++;
printk("Device opened %d times\n", counter);
return 0;
}
int char_driver_close(struct inode *pinode, struct file *pfile) {
printk("Device closed %d times\n", counter);
return 0;
}
ssize_t char_driver_read(struct file *pfile, char __user *buffer, size_t length,
loff_t *offset) {
size_t data_avail = BUFFER_SIZE - *offset, bytes_read = length;
if (*offset >= BUFFER_SIZE || !length)
return 0;
if (length > data_avail)
bytes_read = data_avail;
printk("Requested data size: %zd bytes\n", length);
long res = copy_to_user(buffer, data + *offset, bytes_read);
printk("Read %zd bytes from device\n", bytes_read);
length -= res;
*offset += length;
return length;
}
ssize_t char_driver_write(struct file *pfile, const char __user *buffer,
size_t length, loff_t *offset) {
size_t data_avail = BUFFER_SIZE - *offset, bytes_written = length;
if (*offset >= BUFFER_SIZE || !length)
return 0;
if (length > data_avail)
bytes_written = data_avail;
printk("Requested data size: %zd bytes\n", length);
long res = copy_from_user(data + *offset, buffer, bytes_written);
printk("Wrote %zd bytes to device\n", bytes_written);
length -= res;
*offset += bytes_written;
return length;
}
loff_t char_driver_seek(struct file *pfile, loff_t offset, int whence) {
loff_t new_pos = 0;
switch (whence) {
case SEEK_SET:
new_pos = offset;
break;
case SEEK_CUR:
new_pos = pfile->f_pos + offset;
break;
case SEEK_END:
new_pos = BUFFER_SIZE - offset;
break;
}
if (new_pos > BUFFER_SIZE)
new_pos = BUFFER_SIZE;
if (new_pos < 0)
new_pos = 0;
pfile->f_pos = new_pos;
return new_pos;
}
static int char_driver_init(void) {
printk("Registering device %s\n", DEVICE_NAME);
data = (char *)kmalloc(BUFFER_SIZE * sizeof(char), GFP_KERNEL);
major = register_chrdev(MAJOR_NUM, DEVICE_NAME, &char_fops);
if (major < 0) {
printk(KERN_ALERT "REGISTRATION FAILED: %s could not be reigstered.\n",
DEVICE_NAME);
return -EFAULT;
}
printk("REGISTRATION SUCCESS: %s successfully registered.\n", DEVICE_NAME);
return 0;
}
static void char_driver_exit(void) {
kfree(data);
unregister_chrdev(major, DEVICE_NAME);
printk("UNREGISTER SUCCESS: %s successfully unregistered\n", DEVICE_NAME);
}
module_init(char_driver_init);
module_exit(char_driver_exit);
|