1# SPDX-License-Identifier: GPL-2.0 2config TTY 3 bool "Enable TTY" if EXPERT 4 default y 5 help 6 Allows you to remove TTY support which can save space, and 7 blocks features that require TTY from inclusion in the kernel. 8 TTY is required for any text terminals or serial port 9 communication. Most users should leave this enabled. 10 11if TTY 12 13config VT 14 bool "Virtual terminal" if EXPERT 15 select INPUT 16 default y if !UML 17 help 18 If you say Y here, you will get support for terminal devices with 19 display and keyboard devices. These are called "virtual" because you 20 can run several virtual terminals (also called virtual consoles) on 21 one physical terminal. This is rather useful, for example one 22 virtual terminal can collect system messages and warnings, another 23 one can be used for a text-mode user session, and a third could run 24 an X session, all in parallel. Switching between virtual terminals 25 is done with certain key combinations, usually Alt-<function key>. 26 27 The setterm command ("man setterm") can be used to change the 28 properties (such as colors or beeping) of a virtual terminal. The 29 man page console_codes(4) ("man console_codes") contains the special 30 character sequences that can be used to change those properties 31 directly. The fonts used on virtual terminals can be changed with 32 the setfont ("man setfont") command and the key bindings are defined 33 with the loadkeys ("man loadkeys") command. 34 35 You need at least one virtual terminal device in order to make use 36 of your keyboard and monitor. Therefore, only people configuring an 37 embedded system would want to say N here in order to save some 38 memory; the only way to log into such a system is then via a serial 39 or network connection. 40 41 If unsure, say Y, or else you won't be able to do much with your new 42 shiny Linux system :-) 43 44config CONSOLE_TRANSLATIONS 45 depends on VT 46 default y 47 bool "Enable character translations in console" if EXPERT 48 help 49 This enables support for font mapping and Unicode translation 50 on virtual consoles. 51 52config VT_CONSOLE 53 bool "Support for console on virtual terminal" if EXPERT 54 depends on VT 55 default y 56 help 57 The system console is the device which receives all kernel messages 58 and warnings and which allows logins in single user mode. If you 59 answer Y here, a virtual terminal (the device used to interact with 60 a physical terminal) can be used as system console. This is the most 61 common mode of operations, so you should say Y here unless you want 62 the kernel messages be output only to a serial port (in which case 63 you should say Y to "Console on serial port", below). 64 65 If you do say Y here, by default the currently visible virtual 66 terminal (/dev/tty0) will be used as system console. You can change 67 that with a kernel command line option such as "console=tty3" which 68 would use the third virtual terminal as system console. (Try "man 69 bootparam" or see the documentation of your boot loader (lilo or 70 loadlin) about how to pass options to the kernel at boot time.) 71 72 If unsure, say Y. 73 74config VT_CONSOLE_SLEEP 75 def_bool y 76 depends on VT_CONSOLE && PM_SLEEP 77 78config HW_CONSOLE 79 bool 80 depends on VT 81 default y 82 83config VT_HW_CONSOLE_BINDING 84 bool "Support for binding and unbinding console drivers" 85 depends on HW_CONSOLE 86 help 87 The virtual terminal is the device that interacts with the physical 88 terminal through console drivers. On these systems, at least one 89 console driver is loaded. In other configurations, additional console 90 drivers may be enabled, such as the framebuffer console. If more than 91 1 console driver is enabled, setting this to 'y' will allow you to 92 select the console driver that will serve as the backend for the 93 virtual terminals. 94 95 See <file:Documentation/driver-api/console.rst> for more 96 information. For framebuffer console users, please refer to 97 <file:Documentation/fb/fbcon.rst>. 98 99config UNIX98_PTYS 100 bool "Unix98 PTY support" if EXPERT 101 default y 102 help 103 A pseudo terminal (PTY) is a software device consisting of two 104 halves: a master and a slave. The slave device behaves identical to 105 a physical terminal; the master device is used by a process to 106 read data from and write data to the slave, thereby emulating a 107 terminal. Typical programs for the master side are telnet servers 108 and xterms. 109 110 Linux has traditionally used the BSD-like names /dev/ptyxx for 111 masters and /dev/ttyxx for slaves of pseudo terminals. This scheme 112 has a number of problems. The GNU C library glibc 2.1 and later, 113 however, supports the Unix98 naming standard: in order to acquire a 114 pseudo terminal, a process opens /dev/ptmx; the number of the pseudo 115 terminal is then made available to the process and the pseudo 116 terminal slave can be accessed as /dev/pts/<number>. What was 117 traditionally /dev/ttyp2 will then be /dev/pts/2, for example. 118 119 All modern Linux systems use the Unix98 ptys. Say Y unless 120 you're on an embedded system and want to conserve memory. 121 122config LEGACY_PTYS 123 bool "Legacy (BSD) PTY support" 124 default y 125 help 126 A pseudo terminal (PTY) is a software device consisting of two 127 halves: a master and a slave. The slave device behaves identical to 128 a physical terminal; the master device is used by a process to 129 read data from and write data to the slave, thereby emulating a 130 terminal. Typical programs for the master side are telnet servers 131 and xterms. 132 133 Linux has traditionally used the BSD-like names /dev/ptyxx 134 for masters and /dev/ttyxx for slaves of pseudo 135 terminals. This scheme has a number of problems, including 136 security. This option enables these legacy devices; on most 137 systems, it is safe to say N. 138 139config LEGACY_PTY_COUNT 140 int "Maximum number of legacy PTY in use" 141 depends on LEGACY_PTYS 142 range 0 256 143 default "256" 144 help 145 The maximum number of legacy PTYs that can be used at any one time. 146 The default is 256, and should be more than enough. Embedded 147 systems may want to reduce this to save memory. 148 149 When not in use, each legacy PTY occupies 12 bytes on 32-bit 150 architectures and 24 bytes on 64-bit architectures. 151 152config LEGACY_TIOCSTI 153 bool "Allow legacy TIOCSTI usage" 154 default y 155 help 156 Historically the kernel has allowed TIOCSTI, which will push 157 characters into a controlling TTY. This continues to be used 158 as a malicious privilege escalation mechanism, and provides no 159 meaningful real-world utility any more. Its use is considered 160 a dangerous legacy operation, and can be disabled on most 161 systems. 162 163 Say 'Y here only if you have confirmed that your system's 164 userspace depends on this functionality to continue operating 165 normally. 166 167 This functionality can be changed at runtime with the 168 dev.tty.legacy_tiocsti sysctl. This configuration option sets 169 the default value of the sysctl. 170 171config LDISC_AUTOLOAD 172 bool "Automatically load TTY Line Disciplines" 173 default y 174 help 175 Historically the kernel has always automatically loaded any 176 line discipline that is in a kernel module when a user asks 177 for it to be loaded with the TIOCSETD ioctl, or through other 178 means. This is not always the best thing to do on systems 179 where you know you will not be using some of the more 180 "ancient" line disciplines, so prevent the kernel from doing 181 this unless the request is coming from a process with the 182 CAP_SYS_MODULE permissions. 183 184 Say 'Y' here if you trust your userspace users to do the right 185 thing, or if you have only provided the line disciplines that 186 you know you will be using, or if you wish to continue to use 187 the traditional method of on-demand loading of these modules 188 by any user. 189 190 This functionality can be changed at runtime with the 191 dev.tty.ldisc_autoload sysctl, this configuration option will 192 only set the default value of this functionality. 193 194source "drivers/tty/serial/Kconfig" 195 196config SERIAL_NONSTANDARD 197 bool "Non-standard serial port support" 198 depends on HAS_IOMEM 199 help 200 Say Y here if you have any non-standard serial boards -- boards 201 which aren't supported using the standard "dumb" serial driver. 202 This includes intelligent serial boards such as 203 Digiboards, etc. These are usually used for systems that need many 204 serial ports because they serve many terminals or dial-in 205 connections. 206 207 Note that the answer to this question won't directly affect the 208 kernel: saying N will just cause the configurator to skip all 209 the questions about non-standard serial boards. 210 211 Most people can say N here. 212 213config MOXA_INTELLIO 214 tristate "Moxa Intellio support" 215 depends on SERIAL_NONSTANDARD && (ISA || EISA || PCI) 216 select FW_LOADER 217 help 218 Say Y here if you have a Moxa Intellio multiport serial card. 219 220 To compile this driver as a module, choose M here: the 221 module will be called moxa. 222 223config MOXA_SMARTIO 224 tristate "Moxa SmartIO support v. 2.0" 225 depends on SERIAL_NONSTANDARD && PCI 226 help 227 Say Y here if you have a Moxa SmartIO multiport serial card and/or 228 want to help develop a new version of this driver. 229 230 This is upgraded (1.9.1) driver from original Moxa drivers with 231 changes finally resulting in PCI probing. 232 233 This driver can also be built as a module. The module will be called 234 mxser. If you want to do that, say M here. 235 236config SYNCLINK_GT 237 tristate "SyncLink GT/AC support" 238 depends on SERIAL_NONSTANDARD && PCI 239 help 240 Support for SyncLink GT and SyncLink AC families of 241 synchronous and asynchronous serial adapters 242 manufactured by Microgate Systems, Ltd. (www.microgate.com) 243 244config N_HDLC 245 tristate "HDLC line discipline support" 246 depends on SERIAL_NONSTANDARD 247 help 248 Allows synchronous HDLC communications with tty device drivers that 249 support synchronous HDLC such as the Microgate SyncLink adapter. 250 251 This driver can be built as a module ( = code which can be 252 inserted in and removed from the running kernel whenever you want). 253 The module will be called n_hdlc. If you want to do that, say M 254 here. 255 256config PPC_EPAPR_HV_BYTECHAN 257 bool "ePAPR hypervisor byte channel driver" 258 depends on PPC 259 select EPAPR_PARAVIRT 260 help 261 This driver creates /dev entries for each ePAPR hypervisor byte 262 channel, thereby allowing applications to communicate with byte 263 channels as if they were serial ports. 264 265config PPC_EARLY_DEBUG_EHV_BC 266 bool "Early console (udbg) support for ePAPR hypervisors" 267 depends on PPC_EPAPR_HV_BYTECHAN=y 268 help 269 Select this option to enable early console (a.k.a. "udbg") support 270 via an ePAPR byte channel. You also need to choose the byte channel 271 handle below. 272 273config PPC_EARLY_DEBUG_EHV_BC_HANDLE 274 int "Byte channel handle for early console (udbg)" 275 depends on PPC_EARLY_DEBUG_EHV_BC 276 default 0 277 help 278 If you want early console (udbg) output through a byte channel, 279 specify the handle of the byte channel to use. 280 281 For this to work, the byte channel driver must be compiled 282 in-kernel, not as a module. 283 284 Note that only one early console driver can be enabled, so don't 285 enable any others if you enable this one. 286 287 If the number you specify is not a valid byte channel handle, then 288 there simply will be no early console output. This is true also 289 if you don't boot under a hypervisor at all. 290 291config GOLDFISH_TTY 292 tristate "Goldfish TTY Driver" 293 depends on GOLDFISH 294 select SERIAL_CORE 295 select SERIAL_CORE_CONSOLE 296 help 297 Console and system TTY driver for the Goldfish virtual platform. 298 299config GOLDFISH_TTY_EARLY_CONSOLE 300 bool 301 default y if GOLDFISH_TTY=y 302 select SERIAL_EARLYCON 303 304config N_GSM 305 tristate "GSM MUX line discipline support (EXPERIMENTAL)" 306 depends on NET 307 help 308 This line discipline provides support for the GSM MUX protocol and 309 presents the mux as a set of 61 individual tty devices. 310 311config NOZOMI 312 tristate "HSDPA Broadband Wireless Data Card - Globe Trotter" 313 depends on PCI 314 help 315 If you have a HSDPA driver Broadband Wireless Data Card - 316 Globe Trotter PCMCIA card, say Y here. 317 318 To compile this driver as a module, choose M here, the module 319 will be called nozomi. 320 321config MIPS_EJTAG_FDC_TTY 322 bool "MIPS EJTAG Fast Debug Channel TTY" 323 depends on MIPS_CDMM 324 help 325 This enables a TTY and console on the MIPS EJTAG Fast Debug Channels, 326 if they are present. This can be useful when working with an EJTAG 327 probe which supports it, to get console output and a login prompt via 328 EJTAG without needing to connect a serial cable. 329 330 TTY devices are named e.g. ttyFDC3c2 (for FDC channel 2 of the FDC on 331 CPU3). 332 333 The console can be enabled with console=fdc1 (for FDC channel 1 on all 334 CPUs). Do not use the console unless there is a debug probe attached 335 to drain the FDC TX FIFO. 336 337 If unsure, say N. 338 339config MIPS_EJTAG_FDC_EARLYCON 340 bool "Early FDC console" 341 depends on MIPS_EJTAG_FDC_TTY 342 help 343 This registers a console on FDC channel 1 very early during boot (from 344 MIPS arch code). This is useful for bring-up and debugging early boot 345 issues. 346 347 Do not enable unless there is a debug probe attached to drain the FDC 348 TX FIFO. 349 350 If unsure, say N. 351 352config MIPS_EJTAG_FDC_KGDB 353 bool "Use KGDB over an FDC channel" 354 depends on MIPS_EJTAG_FDC_TTY && KGDB 355 default y 356 help 357 This enables the use of KGDB over an FDC channel, allowing KGDB to be 358 used remotely or when a serial port isn't available. 359 360config MIPS_EJTAG_FDC_KGDB_CHAN 361 int "KGDB FDC channel" 362 depends on MIPS_EJTAG_FDC_KGDB 363 range 2 15 364 default 3 365 help 366 FDC channel number to use for KGDB. 367 368config NULL_TTY 369 tristate "NULL TTY driver" 370 help 371 Say Y here if you want a NULL TTY which simply discards messages. 372 373 This is useful to allow userspace applications which expect a console 374 device to work without modifications even when no console is 375 available or desired. 376 377 In order to use this driver, you should redirect the console to this 378 TTY, or boot the kernel with console=ttynull. 379 380 If unsure, say N. 381 382config VCC 383 tristate "Sun Virtual Console Concentrator" 384 depends on SUN_LDOMS 385 help 386 Support for Sun logical domain consoles. 387 388source "drivers/tty/hvc/Kconfig" 389 390config RPMSG_TTY 391 tristate "RPMSG tty driver" 392 depends on RPMSG 393 help 394 Say y here to export rpmsg endpoints as tty devices, usually found 395 in /dev/ttyRPMSGx. 396 This makes it possible for user-space programs to send and receive 397 rpmsg messages as a standard tty protocol. 398 399 To compile this driver as a module, choose M here: the module will be 400 called rpmsg_tty. 401 402endif # TTY 403 404source "drivers/tty/serdev/Kconfig" 405