Hi!
Goal, when the user do :
# head -1 /dev/miscdrv
The driver prints: Hello World!
Steps:
# Make
# insmod misc.ko
# head -1 /dev/miscdrv
Why my driver doesn't work ?
What is worg with my read operation?
static ssize_t
misc_drv_read(struct file *filp, char __user * buf, size_t count, loff_t * offp){
int nbytes;
char * string = "hello World";
nbytes = copy_to_user(buf, string, 12);
return nbytes;
}
--
Lucas Tanure Brazil
Attachment:
Makefile
Description: Binary data
#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/device.h>
#include <linux/miscdevice.h>
#include <linux/uaccess.h> /* copy_(to,from)_user */
#define MYDEV_NAME "miscdrv"
static ssize_t
misc_drv_read(struct file *filp, char __user * buf, size_t count, loff_t * offp){
int nbytes;
char * string = "hello World";
nbytes = copy_to_user(buf, string, 12);
return nbytes;
}
static ssize_t
misc_drv_write(struct file *filp, const char __user * buf, size_t count, loff_t * offp)
{
return 0;
}
static const struct file_operations misc_drv_fops = {
.read = misc_drv_read,
.write = misc_drv_write,
};
static struct miscdevice my_misc_device = {
.minor = MISC_DYNAMIC_MINOR,
.name = MYDEV_NAME,
.fops = &misc_drv_fops,
};
static int __init my_init(void){
dev_info(my_misc_device.this_device, "Registering Device\n");
if (misc_register(&my_misc_device)) {
pr_err("Couldn't register device misc, %d.\n", my_misc_device.minor);
return -EBUSY;
}
return 0;
}
static void __exit my_exit(void)
{
dev_info(my_misc_device.this_device, "Unregistering Device\n");
misc_deregister(&my_misc_device);
}
module_init(my_init);
module_exit(my_exit);
MODULE_AUTHOR("Lucas Tanure");
MODULE_DESCRIPTION("Test Misc Device");
MODULE_LICENSE("GPL v2");
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