# SPDX-License-Identifier: GPL-2.0config 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 VT_HW_CONSOLE_BINDING	bool "Support for binding and unbinding console drivers"	depends on VT	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. 	  Processes which run with CAP_SYS_ADMIN, such as BRLTTY, can	  use TIOCSTI even when this is set to N. 	  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 && 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 && HAS_IOPORT	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 N_HDLC	tristate "HDLC line discipline support"	depends on SERIAL_NONSTANDARD	help	  Allows synchronous HDLC communications with tty device drivers that	  support synchronous HDLC. 	  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, boot the kernel with console=ttynull, or enable	  NULL_TTY_DEFAULT_CONSOLE. 	  If unsure, say N. config NULL_TTY_DEFAULT_CONSOLE	bool "Support for console on ttynull"	depends on NULL_TTY=y && !VT_CONSOLE	help	  Say Y here if you want the NULL TTY to be used as a /dev/console	  device by default. 	  For example, it might be useful to prevent a VT-less kernel from	  writing the system log to a random device connected to the serial	  port. 	  Another console driver still might get preferred via the command	  line, SPCR, or the device tree. 	  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"