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// Jack Sangdahl
// CSCI3753 SP24
// PA3 Device Driver
#include <linux/fs.h>
#include <linux/module.h>
MODULE_AUTHOR("jasa7131");
MODULE_LICENSE("GPL");
#define BUFFER_SIZE 900
#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) {
ssize_t data_read = simple_read_from_buffer(buffer, length, offset,
data + *offset, BUFFER_SIZE);
if (data_read < 0) {
printk("READ FAILED: Failed to read from user buffer.\n");
return -EFAULT;
}
if (data_read) {
printk("READ SUCCESS: Read %ld bytes from %s.\n", data_read, DEVICE_NAME);
if (data_read >= BUFFER_SIZE)
printk("Reached EOF\n");
}
return data_read;
}
ssize_t char_driver_write(struct file *pfile, const char __user *buffer,
size_t length, loff_t *offset) {
ssize_t data_written = simple_write_to_buffer(data + *offset, BUFFER_SIZE,
offset, buffer, length);
printk("WRITE SUCCESS: Wrote %ld bytes to %s.\n", data_written, DEVICE_NAME);
if (data_written > BUFFER_SIZE)
printk("WRITE ERR: Buffer is filled.\n");
return data_written;
}
loff_t char_driver_seek(struct file *pfile, loff_t offset, int whence) {
switch (whence) {
case SEEK_SET:
pfile->f_pos = offset;
break;
case SEEK_CUR:
pfile->f_pos += offset;
break;
case SEEK_END:
pfile->f_pos = strlen(data) - offset;
break;
}
return pfile->f_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(511, 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);
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