Greetings, My I2C sensor driver has a debugfs entry for development purposes. Everything works fine with the exception of the read operation. When 'cat' is used, the read operation is called repeatedly and indefinitely. If the read() is changed to return 0 then, as expected, nothing is displayed. The pattern for the implementation is (AFAICT) right out of the book (shown below). What am I missing? Any thoughts much appreciated. TAIA. RDQ static ssize_t sc031gs_reg_read_file(struct file *file, char __user *user_buf, size_t count, loff_t *ppos) { char *buf = 0; ssize_t total = 0; struct sc031gs_dev *sensor = file->private_data; if (!sensor) return -EINVAL; if (*ppos < 0 || !count) return -EINVAL; buf = kmalloc(count, GFP_KERNEL); if (!buf) return -ENOMEM; total = snprintf(buf,count,"Hello world\n"); if (total >= 0) { if (copy_to_user(user_buf, buf, total)) { kfree(buf); return -EFAULT; } *ppos += total; } kfree(buf); return total; }