My device /dev/my_inc is meant to take a positive integer N represented as an ascii string, and store it. Any read from /dev/my_inc will produce the ascii string representation of N + 1.

The problem is that when I cat /dev/my_inc, I only get the first byte of myinc_value output to my shell, even though I have bytes_read == 2 at the end of my loop.

/* Read from the device 
 *********************/
static ssize_t device_read(struct file *filp, char *buffer, size_t length, loff_t *offset)
{
    char c;
    int bytes_read  = 0;
    int value   = myinc_value + 1;

    printk(KERN_INFO "my_inc device_read() called with value %d and msg %s.\n", value, msg);

    /* No bytes read if pointer to 0 */
    if (*msg_ptr == 0) 
        return 0;

    /* Put the incremented value in msg */
    snprintf(msg, MAX_LENGTH, "%d", value);

    /* Put bytes from msg into user space buffer */
    while (length && *msg_ptr) 
    {
        c = *(msg_ptr++);
        printk(KERN_INFO "%s device_read() read %c.", DEV_NAME, c);

        if(put_user(c, buffer++))
            return -EFAULT;
        length--;
        bytes_read++;
    }

    printk("my_inc device_read() returning %d.\n", bytes_read);

    /* Return bytes copied */
    return bytes_read;
}