# SPDX-License-Identifier: GPL-2.0
config TTY
bool "Enable TTY" if EXPERT
default y
help
Allows you to remove TTY support which can save space, and
blocks features that require TTY from inclusion in the kernel.
TTY is required for any text terminals or serial port
communication. Most users should leave this enabled.
if TTY
config VT
bool "Virtual terminal" if EXPERT
select INPUT
default y if !UML
help
If you say Y here, you will get support for terminal devices with
display and keyboard devices. These are called "virtual" because you
can run several virtual terminals (also called virtual consoles) on
one physical terminal. This is rather useful, for example one
virtual terminal can collect system messages and warnings, another
one can be used for a text-mode user session, and a third could run
an X session, all in parallel. Switching between virtual terminals
is done with certain key combinations, usually Alt-<function key>.
The setterm command ("man setterm") can be used to change the
properties (such as colors or beeping) of a virtual terminal. The
man page console_codes(4) ("man console_codes") contains the special
character sequences that can be used to change those properties
directly. The fonts used on virtual terminals can be changed with
the setfont ("man setfont") command and the key bindings are defined
with the loadkeys ("man loadkeys") command.
You need at least one virtual terminal device in order to make use
of your keyboard and monitor. Therefore, only people configuring an
embedded system would want to say N here in order to save some
memory; the only way to log into such a system is then via a serial
or network connection.
If unsure, say Y, or else you won't be able to do much with your new
shiny Linux system :-)
config CONSOLE_TRANSLATIONS
depends on VT
default y
bool "Enable character translations in console" if EXPERT
help
This enables support for font mapping and Unicode translation
on virtual consoles.
config VT_CONSOLE
bool "Support for console on virtual terminal" if EXPERT
depends on VT
default y
help
The system console is the device which receives all kernel messages
and warnings and which allows logins in single user mode. If you
answer Y here, a virtual terminal (the device used to interact with
a physical terminal) can be used as system console. This is the most
common mode of operations, so you should say Y here unless you want
the kernel messages be output only to a serial port (in which case
you should say Y to "Console on serial port", below).
If you do say Y here, by default the currently visible virtual
terminal (/dev/tty0) will be used as system console. You can change
that with a kernel command line option such as "console=tty3" which
would use the third virtual terminal as system console. (Try "man
bootparam" or see the documentation of your boot loader (lilo or
loadlin) about how to pass options to the kernel at boot time.)
If unsure, say Y.
config VT_CONSOLE_SLEEP
def_bool y
depends on VT_CONSOLE && PM_SLEEP
config HW_CONSOLE
bool
depends on VT
default y
config VT_HW_CONSOLE_BINDING
bool "Support for binding and unbinding console drivers"
depends on HW_CONSOLE
help
The virtual terminal is the device that interacts with the physical
terminal through console drivers. On these systems, at least one
console driver is loaded. In other configurations, additional console
drivers may be enabled, such as the framebuffer console. If more than
1 console driver is enabled, setting this to 'y' will allow you to
select the console driver that will serve as the backend for the
virtual terminals.
See <file:Documentation/driver-api/console.rst> for more
information. For framebuffer console users, please refer to
<file:Documentation/fb/fbcon.rst>.
config UNIX98_PTYS
bool "Unix98 PTY support" if EXPERT
default y
help
A pseudo terminal (PTY) is a software device consisting of two
halves: a master and a slave. The slave device behaves identical to
a physical terminal; the master device is used by a process to
read data from and write data to the slave, thereby emulating a
terminal. Typical programs for the master side are telnet servers
and xterms.
Linux has traditionally used the BSD-like names /dev/ptyxx for
masters and /dev/ttyxx for slaves of pseudo terminals. This scheme
has a number of problems. The GNU C library glibc 2.1 and later,
however, supports the Unix98 naming standard: in order to acquire a
pseudo terminal, a process opens /dev/ptmx; the number of the pseudo
terminal is then made available to the process and the pseudo
terminal slave can be accessed as /dev/pts/<number>. What was
traditionally /dev/ttyp2 will then be /dev/pts/2, for example.
All modern Linux systems use the Unix98 ptys. Say Y unless
you're on an embedded system and want to conserve memory.
config LEGACY_PTYS
bool "Legacy (BSD) PTY support"
default y
help
A pseudo terminal (PTY) is a software device consisting of two
halves: a master and a slave. The slave device behaves identical to
a physical terminal; the master device is used by a process to
read data from and write data to the slave, thereby emulating a
terminal. Typical programs for the master side are telnet servers
and xterms.
Linux has traditionally used the BSD-like names /dev/ptyxx
for masters and /dev/ttyxx for slaves of pseudo
terminals. This scheme has a number of problems, including
security. This option enables these legacy devices; on most
systems, it is safe to say N.
config LEGACY_PTY_COUNT
int "Maximum number of legacy PTY in use"
depends on LEGACY_PTYS
range 0 256
default "256"
help
The maximum number of legacy PTYs that can be used at any one time.
The default is 256, and should be more than enough. Embedded
systems may want to reduce this to save memory.
When not in use, each legacy PTY occupies 12 bytes on 32-bit
architectures and 24 bytes on 64-bit architectures.
config LEGACY_TIOCSTI
bool "Allow legacy TIOCSTI usage"
default y
help
Historically the kernel has allowed TIOCSTI, which will push
characters into a controlling TTY. This continues to be used
as a malicious privilege escalation mechanism, and provides no
meaningful real-world utility any more. Its use is considered
a dangerous legacy operation, and can be disabled on most
systems.
Say 'Y here only if you have confirmed that your system's
userspace depends on this functionality to continue operating
normally.
This functionality can be changed at runtime with the
dev.tty.legacy_tiocsti sysctl. This configuration option sets
the default value of the sysctl.
config LDISC_AUTOLOAD
bool "Automatically load TTY Line Disciplines"
default y
help
Historically the kernel has always automatically loaded any
line discipline that is in a kernel module when a user asks
for it to be loaded with the TIOCSETD ioctl, or through other
means. This is not always the best thing to do on systems
where you know you will not be using some of the more
"ancient" line disciplines, so prevent the kernel from doing
this unless the request is coming from a process with the
CAP_SYS_MODULE permissions.
Say 'Y' here if you trust your userspace users to do the right
thing, or if you have only provided the line disciplines that
you know you will be using, or if you wish to continue to use
the traditional method of on-demand loading of these modules
by any user.
This functionality can be changed at runtime with the
dev.tty.ldisc_autoload sysctl, this configuration option will
only set the default value of this functionality.
source "drivers/tty/serial/Kconfig"
config SERIAL_NONSTANDARD
bool "Non-standard serial port support"
depends on HAS_IOMEM
help
Say Y here if you have any non-standard serial boards -- boards
which aren't supported using the standard "dumb" serial driver.
This includes intelligent serial boards such as
Digiboards, etc. These are usually used for systems that need many
serial ports because they serve many terminals or dial-in
connections.
Note that the answer to this question won't directly affect the
kernel: saying N will just cause the configurator to skip all
the questions about non-standard serial boards.
Most people can say N here.
config MOXA_INTELLIO
tristate "Moxa Intellio support"
depends on SERIAL_NONSTANDARD && (ISA || EISA || PCI)
select FW_LOADER
help
Say Y here if you have a Moxa Intellio multiport serial card.
To compile this driver as a module, choose M here: the
module will be called moxa.
config MOXA_SMARTIO
tristate "Moxa SmartIO support v. 2.0"
depends on SERIAL_NONSTANDARD && PCI
help
Say Y here if you have a Moxa SmartIO multiport serial card and/or
want to help develop a new version of this driver.
This is upgraded (1.9.1) driver from original Moxa drivers with
changes finally resulting in PCI probing.
This driver can also be built as a module. The module will be called
mxser. If you want to do that, say M here.
config SYNCLINK_GT
tristate "SyncLink GT/AC support"
depends on SERIAL_NONSTANDARD && PCI
help
Support for SyncLink GT and SyncLink AC families of
synchronous and asynchronous serial adapters
manufactured by Microgate Systems, Ltd. (www.microgate.com)
config N_HDLC
tristate "HDLC line discipline support"
depends on SERIAL_NONSTANDARD
help
Allows synchronous HDLC communications with tty device drivers that
support synchronous HDLC such as the Microgate SyncLink adapter.
This driver can be built as a module ( = code which can be
inserted in and removed from the running kernel whenever you want).
The module will be called n_hdlc. If you want to do that, say M
here.
config PPC_EPAPR_HV_BYTECHAN
bool "ePAPR hypervisor byte channel driver"
depends on PPC
select EPAPR_PARAVIRT
help
This driver creates /dev entries for each ePAPR hypervisor byte
channel, thereby allowing applications to communicate with byte
channels as if they were serial ports.
config PPC_EARLY_DEBUG_EHV_BC
bool "Early console (udbg) support for ePAPR hypervisors"
depends on PPC_EPAPR_HV_BYTECHAN=y
help
Select this option to enable early console (a.k.a. "udbg") support
via an ePAPR byte channel. You also need to choose the byte channel
handle below.
config PPC_EARLY_DEBUG_EHV_BC_HANDLE
int "Byte channel handle for early console (udbg)"
depends on PPC_EARLY_DEBUG_EHV_BC
default 0
help
If you want early console (udbg) output through a byte channel,
specify the handle of the byte channel to use.
For this to work, the byte channel driver must be compiled
in-kernel, not as a module.
Note that only one early console driver can be enabled, so don't
enable any others if you enable this one.
If the number you specify is not a valid byte channel handle, then
there simply will be no early console output. This is true also
if you don't boot under a hypervisor at all.
config GOLDFISH_TTY
tristate "Goldfish TTY Driver"
depends on GOLDFISH
select SERIAL_CORE
select SERIAL_CORE_CONSOLE
help
Console and system TTY driver for the Goldfish virtual platform.
config GOLDFISH_TTY_EARLY_CONSOLE
bool
default y if GOLDFISH_TTY=y
select SERIAL_EARLYCON
config N_GSM
tristate "GSM MUX line discipline support (EXPERIMENTAL)"
depends on NET
help
This line discipline provides support for the GSM MUX protocol and
presents the mux as a set of 61 individual tty devices.
config NOZOMI
tristate "HSDPA Broadband Wireless Data Card - Globe Trotter"
depends on PCI
help
If you have a HSDPA driver Broadband Wireless Data Card -
Globe Trotter PCMCIA card, say Y here.
To compile this driver as a module, choose M here, the module
will be called nozomi.
config MIPS_EJTAG_FDC_TTY
bool "MIPS EJTAG Fast Debug Channel TTY"
depends on MIPS_CDMM
help
This enables a TTY and console on the MIPS EJTAG Fast Debug Channels,
if they are present. This can be useful when working with an EJTAG
probe which supports it, to get console output and a login prompt via
EJTAG without needing to connect a serial cable.
TTY devices are named e.g. ttyFDC3c2 (for FDC channel 2 of the FDC on
CPU3).
The console can be enabled with console=fdc1 (for FDC channel 1 on all
CPUs). Do not use the console unless there is a debug probe attached
to drain the FDC TX FIFO.
If unsure, say N.
config MIPS_EJTAG_FDC_EARLYCON
bool "Early FDC console"
depends on MIPS_EJTAG_FDC_TTY
help
This registers a console on FDC channel 1 very early during boot (from
MIPS arch code). This is useful for bring-up and debugging early boot
issues.
Do not enable unless there is a debug probe attached to drain the FDC
TX FIFO.
If unsure, say N.
config MIPS_EJTAG_FDC_KGDB
bool "Use KGDB over an FDC channel"
depends on MIPS_EJTAG_FDC_TTY && KGDB
default y
help
This enables the use of KGDB over an FDC channel, allowing KGDB to be
used remotely or when a serial port isn't available.
config MIPS_EJTAG_FDC_KGDB_CHAN
int "KGDB FDC channel"
depends on MIPS_EJTAG_FDC_KGDB
range 2 15
default 3
help
FDC channel number to use for KGDB.
config NULL_TTY
tristate "NULL TTY driver"
help
Say Y here if you want a NULL TTY which simply discards messages.
This is useful to allow userspace applications which expect a console
device to work without modifications even when no console is
available or desired.
In order to use this driver, you should redirect the console to this
TTY, or boot the kernel with console=ttynull.
If unsure, say N.
config VCC
tristate "Sun Virtual Console Concentrator"
depends on SUN_LDOMS
help
Support for Sun logical domain consoles.
source "drivers/tty/hvc/Kconfig"
config RPMSG_TTY
tristate "RPMSG tty driver"
depends on RPMSG
help
Say y here to export rpmsg endpoints as tty devices, usually found
in /dev/ttyRPMSGx.
This makes it possible for user-space programs to send and receive
rpmsg messages as a standard tty protocol.
To compile this driver as a module, choose M here: the module will be
called rpmsg_tty.
endif # TTY
source "drivers/tty/serdev/Kconfig"
