// SPDX-License-Identifier: GPL-2.0+
/*
* IBM eServer Hypervisor Virtual Console Server Device Driver
* Copyright (C) 2003, 2004 IBM Corp.
* Ryan S. Arnold (rsa@us.ibm.com)
*
* Author(s) : Ryan S. Arnold <rsa@us.ibm.com>
*
* This is the device driver for the IBM Hypervisor Virtual Console Server,
* "hvcs". The IBM hvcs provides a tty driver interface to allow Linux
* user space applications access to the system consoles of logically
* partitioned operating systems, e.g. Linux, running on the same partitioned
* Power5 ppc64 system. Physical hardware consoles per partition are not
* practical on this hardware so system consoles are accessed by this driver
* using inter-partition firmware interfaces to virtual terminal devices.
*
* A vty is known to the HMC as a "virtual serial server adapter". It is a
* virtual terminal device that is created by firmware upon partition creation
* to act as a partitioned OS's console device.
*
* Firmware dynamically (via hotplug) exposes vty-servers to a running ppc64
* Linux system upon their creation by the HMC or their exposure during boot.
* The non-user interactive backend of this driver is implemented as a vio
* device driver so that it can receive notification of vty-server lifetimes
* after it registers with the vio bus to handle vty-server probe and remove
* callbacks.
*
* Many vty-servers can be configured to connect to one vty, but a vty can
* only be actively connected to by a single vty-server, in any manner, at one
* time. If the HMC
