* This routine is called by the kernel to write a series of
* characters to the tty device. The characters may come from
* user space or kernel space. This routine will return the
- * number of characters actually accepted for writing. This
- * routine is mandatory.
+ * number of characters actually accepted for writing.
*
* Optional: Required for writable devices.
*
* This routine notifies the tty driver that input buffers for
* the line discipline are close to full, and it should somehow
* signal that no more characters should be sent to the tty.
+ *
+ * Optional: Always invoke via tty_throttle();
*
* void (*unthrottle)(struct tty_struct * tty);
*
* that characters can now be sent to the tty without fear of
* overrunning the input buffers of the line disciplines.
*
+ * Optional: Always invoke via tty_unthrottle();
+ *
* void (*stop)(struct tty_struct *tty);
*
* This routine notifies the tty driver that it should stop
* This routine notifies the tty driver that it should hangup the
* tty device.
*
- * Required:
+ * Optional:
*
* void (*break_ctl)(struct tty_stuct *tty, int state);
*