I am learning how to write a char device module. It compiles fine and sort of
works.
1) using the semaphores causes a segfault, which is why they are commented out
2) a user program using open on the device works, but gets 3 garbage
characters at the end of the string
3) cat on the device just prints the line for ever
What am I doing wrong, or not doing at all?
ssize_t my_read(struct file * filp, char * buf, size_t count, loff_t * fpos)
{
ssize_t ret;
struct semaphore sem;
char my_buf[] = "This is a test of what it can do.";
//if (down_interruptible(&sem))
// return -ERESTARTSYS;
if(count > strlen(my_buf))
count = strlen(my_buf);
ret = copy_to_user(buf, my_buf, count);
//up(&sem);
return count - ret;
}
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