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 Processes which run with CAP_SYS_ADMIN, such as BRLTTY, can 168 use TIOCSTI even when this is set to N. 169 170 This functionality can be changed at runtime with the 171 dev.tty.legacy_tiocsti sysctl. This configuration option sets 172 the default value of the sysctl. 173 174config LDISC_AUTOLOAD 175 bool "Automatically load TTY Line Disciplines" 176 default y 177 help 178 Historically the kernel has always automatically loaded any 179 line discipline that is in a kernel module when a user asks 180 for it to be loaded with the TIOCSETD ioctl, or through other 181 means. This is not always the best thing to do on systems 182 where you know you will not be using some of the more 183 "ancient" line disciplines, so prevent the kernel from doing 184 this unless the request is coming from a process with the 185 CAP_SYS_MODULE permissions. 186 187 Say 'Y' here if you trust your userspace users to do the right 188 thing, or if you have only provided the line disciplines that 189 you know you will be using, or if you wish to continue to use 190 the traditional method of on-demand loading of these modules 191 by any user. 192 193 This functionality can be changed at runtime with the 194 dev.tty.ldisc_autoload sysctl, this configuration option will 195 only set the default value of this functionality. 196 197source "drivers/tty/serial/Kconfig" 198 199config SERIAL_NONSTANDARD 200 bool "Non-standard serial port support" 201 depends on HAS_IOMEM 202 help 203 Say Y here if you have any non-standard serial boards -- boards 204 which aren't supported using the standard "dumb" serial driver. 205 This includes intelligent serial boards such as 206 Digiboards, etc. These are usually used for systems that need many 207 serial ports because they serve many terminals or dial-in 208 connections. 209 210 Note that the answer to this question won't directly affect the 211 kernel: saying N will just cause the configurator to skip all 212 the questions about non-standard serial boards. 213 214 Most people can say N here. 215 216config MOXA_INTELLIO 217 tristate "Moxa Intellio support" 218 depends on SERIAL_NONSTANDARD && (ISA || EISA || PCI) 219 select FW_LOADER 220 help 221 Say Y here if you have a Moxa Intellio multiport serial card. 222 223 To compile this driver as a module, choose M here: the 224 module will be called moxa. 225 226config MOXA_SMARTIO 227 tristate "Moxa SmartIO support v. 2.0" 228 depends on SERIAL_NONSTANDARD && PCI 229 help 230 Say Y here if you have a Moxa SmartIO multiport serial card and/or 231 want to help develop a new version of this driver. 232 233 This is upgraded (1.9.1) driver from original Moxa drivers with 234 changes finally resulting in PCI probing. 235 236 This driver can also be built as a module. The module will be called 237 mxser. If you want to do that, say M here. 238 239config SYNCLINK_GT 240 tristate "SyncLink GT/AC support" 241 depends on SERIAL_NONSTANDARD && PCI 242 help 243 Support for SyncLink GT and SyncLink AC families of 244 synchronous and asynchronous serial adapters 245 manufactured by Microgate Systems, Ltd. (www.microgate.com) 246 247config N_HDLC 248 tristate "HDLC line discipline support" 249 depends on SERIAL_NONSTANDARD 250 help 251 Allows synchronous HDLC communications with tty device drivers that 252 support synchronous HDLC such as the Microgate SyncLink adapter. 253 254 This driver can be built as a module ( = code which can be 255 inserted in and removed from the running kernel whenever you want). 256 The module will be called n_hdlc. If you want to do that, say M 257 here. 258 259config PPC_EPAPR_HV_BYTECHAN 260 bool "ePAPR hypervisor byte channel driver" 261 depends on PPC 262 select EPAPR_PARAVIRT 263 help 264 This driver creates /dev entries for each ePAPR hypervisor byte 265 channel, thereby allowing applications to communicate with byte 266 channels as if they were serial ports. 267 268config PPC_EARLY_DEBUG_EHV_BC 269 bool "Early console (udbg) support for ePAPR hypervisors" 270 depends on PPC_EPAPR_HV_BYTECHAN=y 271 help 272 Select this option to enable early console (a.k.a. "udbg") support 273 via an ePAPR byte channel. You also need to choose the byte channel 274 handle below. 275 276config PPC_EARLY_DEBUG_EHV_BC_HANDLE 277 int "Byte channel handle for early console (udbg)" 278 depends on PPC_EARLY_DEBUG_EHV_BC 279 default 0 280 help 281 If you want early console (udbg) output through a byte channel, 282 specify the handle of the byte channel to use. 283 284 For this to work, the byte channel driver must be compiled 285 in-kernel, not as a module. 286 287 Note that only one early console driver can be enabled, so don't 288 enable any others if you enable this one. 289 290 If the number you specify is not a valid byte channel handle, then 291 there simply will be no early console output. This is true also 292 if you don't boot under a hypervisor at all. 293 294config GOLDFISH_TTY 295 tristate "Goldfish TTY Driver" 296 depends on GOLDFISH 297 select SERIAL_CORE 298 select SERIAL_CORE_CONSOLE 299 help 300 Console and system TTY driver for the Goldfish virtual platform. 301 302config GOLDFISH_TTY_EARLY_CONSOLE 303 bool 304 default y if GOLDFISH_TTY=y 305 select SERIAL_EARLYCON 306 307config IPWIRELESS 308 tristate "IPWireless 3G UMTS PCMCIA card support" 309 depends on PCMCIA && NETDEVICES 310 select PPP 311 help 312 This is a driver for 3G UMTS PCMCIA card from IPWireless company. In 313 some countries (for example Czech Republic, T-Mobile ISP) this card 314 is shipped for service called UMTS 4G. 315 316config N_GSM 317 tristate "GSM MUX line discipline support (EXPERIMENTAL)" 318 depends on NET 319 help 320 This line discipline provides support for the GSM MUX protocol and 321 presents the mux as a set of 61 individual tty devices. 322 323config NOZOMI 324 tristate "HSDPA Broadband Wireless Data Card - Globe Trotter" 325 depends on PCI 326 help 327 If you have a HSDPA driver Broadband Wireless Data Card - 328 Globe Trotter PCMCIA card, say Y here. 329 330 To compile this driver as a module, choose M here, the module 331 will be called nozomi. 332 333config MIPS_EJTAG_FDC_TTY 334 bool "MIPS EJTAG Fast Debug Channel TTY" 335 depends on MIPS_CDMM 336 help 337 This enables a TTY and console on the MIPS EJTAG Fast Debug Channels, 338 if they are present. This can be useful when working with an EJTAG 339 probe which supports it, to get console output and a login prompt via 340 EJTAG without needing to connect a serial cable. 341 342 TTY devices are named e.g. ttyFDC3c2 (for FDC channel 2 of the FDC on 343 CPU3). 344 345 The console can be enabled with console=fdc1 (for FDC channel 1 on all 346 CPUs). Do not use the console unless there is a debug probe attached 347 to drain the FDC TX FIFO. 348 349 If unsure, say N. 350 351config MIPS_EJTAG_FDC_EARLYCON 352 bool "Early FDC console" 353 depends on MIPS_EJTAG_FDC_TTY 354 help 355 This registers a console on FDC channel 1 very early during boot (from 356 MIPS arch code). This is useful for bring-up and debugging early boot 357 issues. 358 359 Do not enable unless there is a debug probe attached to drain the FDC 360 TX FIFO. 361 362 If unsure, say N. 363 364config MIPS_EJTAG_FDC_KGDB 365 bool "Use KGDB over an FDC channel" 366 depends on MIPS_EJTAG_FDC_TTY && KGDB 367 default y 368 help 369 This enables the use of KGDB over an FDC channel, allowing KGDB to be 370 used remotely or when a serial port isn't available. 371 372config MIPS_EJTAG_FDC_KGDB_CHAN 373 int "KGDB FDC channel" 374 depends on MIPS_EJTAG_FDC_KGDB 375 range 2 15 376 default 3 377 help 378 FDC channel number to use for KGDB. 379 380config NULL_TTY 381 tristate "NULL TTY driver" 382 help 383 Say Y here if you want a NULL TTY which simply discards messages. 384 385 This is useful to allow userspace applications which expect a console 386 device to work without modifications even when no console is 387 available or desired. 388 389 In order to use this driver, you should redirect the console to this 390 TTY, or boot the kernel with console=ttynull. 391 392 If unsure, say N. 393 394config VCC 395 tristate "Sun Virtual Console Concentrator" 396 depends on SUN_LDOMS 397 help 398 Support for Sun logical domain consoles. 399 400source "drivers/tty/hvc/Kconfig" 401 402config RPMSG_TTY 403 tristate "RPMSG tty driver" 404 depends on RPMSG 405 help 406 Say y here to export rpmsg endpoints as tty devices, usually found 407 in /dev/ttyRPMSGx. 408 This makes it possible for user-space programs to send and receive 409 rpmsg messages as a standard tty protocol. 410 411 To compile this driver as a module, choose M here: the module will be 412 called rpmsg_tty. 413 414endif # TTY 415 416source "drivers/tty/serdev/Kconfig" 417