1 # SPDX-License-Identifier: GPL-2.0 2 config 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 11 if TTY 12 13 config 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 44 config 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 52 config 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 74 config VT_CONSOLE_SLEEP 75 def_bool y 76 depends on VT_CONSOLE && PM_SLEEP 77 78 config VT_HW_CONSOLE_BINDING 79 bool "Support for binding and unbinding console drivers" 80 depends on VT 81 help 82 The virtual terminal is the device that interacts with the physical 83 terminal through console drivers. On these systems, at least one 84 console driver is loaded. In other configurations, additional console 85 drivers may be enabled, such as the framebuffer console. If more than 86 1 console driver is enabled, setting this to 'y' will allow you to 87 select the console driver that will serve as the backend for the 88 virtual terminals. 89 90 See <file:Documentation/driver-api/console.rst> for more 91 information. For framebuffer console users, please refer to 92 <file:Documentation/fb/fbcon.rst>. 93 94 config UNIX98_PTYS 95 bool "Unix98 PTY support" if EXPERT 96 default y 97 help 98 A pseudo terminal (PTY) is a software device consisting of two 99 halves: a master and a slave. The slave device behaves identical to 100 a physical terminal; the master device is used by a process to 101 read data from and write data to the slave, thereby emulating a 102 terminal. Typical programs for the master side are telnet servers 103 and xterms. 104 105 Linux has traditionally used the BSD-like names /dev/ptyxx for 106 masters and /dev/ttyxx for slaves of pseudo terminals. This scheme 107 has a number of problems. The GNU C library glibc 2.1 and later, 108 however, supports the Unix98 naming standard: in order to acquire a 109 pseudo terminal, a process opens /dev/ptmx; the number of the pseudo 110 terminal is then made available to the process and the pseudo 111 terminal slave can be accessed as /dev/pts/<number>. What was 112 traditionally /dev/ttyp2 will then be /dev/pts/2, for example. 113 114 All modern Linux systems use the Unix98 ptys. Say Y unless 115 you're on an embedded system and want to conserve memory. 116 117 config LEGACY_PTYS 118 bool "Legacy (BSD) PTY support" 119 default y 120 help 121 A pseudo terminal (PTY) is a software device consisting of two 122 halves: a master and a slave. The slave device behaves identical to 123 a physical terminal; the master device is used by a process to 124 read data from and write data to the slave, thereby emulating a 125 terminal. Typical programs for the master side are telnet servers 126 and xterms. 127 128 Linux has traditionally used the BSD-like names /dev/ptyxx 129 for masters and /dev/ttyxx for slaves of pseudo 130 terminals. This scheme has a number of problems, including 131 security. This option enables these legacy devices; on most 132 systems, it is safe to say N. 133 134 config LEGACY_PTY_COUNT 135 int "Maximum number of legacy PTY in use" 136 depends on LEGACY_PTYS 137 range 0 256 138 default "256" 139 help 140 The maximum number of legacy PTYs that can be used at any one time. 141 The default is 256, and should be more than enough. Embedded 142 systems may want to reduce this to save memory. 143 144 When not in use, each legacy PTY occupies 12 bytes on 32-bit 145 architectures and 24 bytes on 64-bit architectures. 146 147 config LEGACY_TIOCSTI 148 bool "Allow legacy TIOCSTI usage" 149 default y 150 help 151 Historically the kernel has allowed TIOCSTI, which will push 152 characters into a controlling TTY. This continues to be used 153 as a malicious privilege escalation mechanism, and provides no 154 meaningful real-world utility any more. Its use is considered 155 a dangerous legacy operation, and can be disabled on most 156 systems. 157 158 Say Y here only if you have confirmed that your system's 159 userspace depends on this functionality to continue operating 160 normally. 161 162 Processes which run with CAP_SYS_ADMIN, such as BRLTTY, can 163 use TIOCSTI even when this is set to N. 164 165 This functionality can be changed at runtime with the 166 dev.tty.legacy_tiocsti sysctl. This configuration option sets 167 the default value of the sysctl. 168 169 config LDISC_AUTOLOAD 170 bool "Automatically load TTY Line Disciplines" 171 default y 172 help 173 Historically the kernel has always automatically loaded any 174 line discipline that is in a kernel module when a user asks 175 for it to be loaded with the TIOCSETD ioctl, or through other 176 means. This is not always the best thing to do on systems 177 where you know you will not be using some of the more 178 "ancient" line disciplines, so prevent the kernel from doing 179 this unless the request is coming from a process with the 180 CAP_SYS_MODULE permissions. 181 182 Say 'Y' here if you trust your userspace users to do the right 183 thing, or if you have only provided the line disciplines that 184 you know you will be using, or if you wish to continue to use 185 the traditional method of on-demand loading of these modules 186 by any user. 187 188 This functionality can be changed at runtime with the 189 dev.tty.ldisc_autoload sysctl, this configuration option will 190 only set the default value of this functionality. 191 192 source "drivers/tty/serial/Kconfig" 193 194 config SERIAL_NONSTANDARD 195 bool "Non-standard serial port support" 196 depends on HAS_IOMEM 197 help 198 Say Y here if you have any non-standard serial boards -- boards 199 which aren't supported using the standard "dumb" serial driver. 200 This includes intelligent serial boards such as 201 Digiboards, etc. These are usually used for systems that need many 202 serial ports because they serve many terminals or dial-in 203 connections. 204 205 Note that the answer to this question won't directly affect the 206 kernel: saying N will just cause the configurator to skip all 207 the questions about non-standard serial boards. 208 209 Most people can say N here. 210 211 config MOXA_INTELLIO 212 tristate "Moxa Intellio support" 213 depends on SERIAL_NONSTANDARD && (ISA || EISA || PCI) 214 select FW_LOADER 215 help 216 Say Y here if you have a Moxa Intellio multiport serial card. 217 218 To compile this driver as a module, choose M here: the 219 module will be called moxa. 220 221 config MOXA_SMARTIO 222 tristate "Moxa SmartIO support v. 2.0" 223 depends on SERIAL_NONSTANDARD && PCI 224 help 225 Say Y here if you have a Moxa SmartIO multiport serial card and/or 226 want to help develop a new version of this driver. 227 228 This is upgraded (1.9.1) driver from original Moxa drivers with 229 changes finally resulting in PCI probing. 230 231 This driver can also be built as a module. The module will be called 232 mxser. If you want to do that, say M here. 233 234 config SYNCLINK_GT 235 tristate "SyncLink GT/AC support" 236 depends on SERIAL_NONSTANDARD && PCI 237 depends on BROKEN 238 help 239 Support for SyncLink GT and SyncLink AC families of 240 synchronous and asynchronous serial adapters 241 manufactured by Microgate Systems, Ltd. (www.microgate.com) 242 243 config N_HDLC 244 tristate "HDLC line discipline support" 245 depends on SERIAL_NONSTANDARD 246 help 247 Allows synchronous HDLC communications with tty device drivers that 248 support synchronous HDLC such as the Microgate SyncLink adapter. 249 250 This driver can be built as a module ( = code which can be 251 inserted in and removed from the running kernel whenever you want). 252 The module will be called n_hdlc. If you want to do that, say M 253 here. 254 255 config PPC_EPAPR_HV_BYTECHAN 256 bool "ePAPR hypervisor byte channel driver" 257 depends on PPC 258 select EPAPR_PARAVIRT 259 help 260 This driver creates /dev entries for each ePAPR hypervisor byte 261 channel, thereby allowing applications to communicate with byte 262 channels as if they were serial ports. 263 264 config PPC_EARLY_DEBUG_EHV_BC 265 bool "Early console (udbg) support for ePAPR hypervisors" 266 depends on PPC_EPAPR_HV_BYTECHAN=y 267 help 268 Select this option to enable early console (a.k.a. "udbg") support 269 via an ePAPR byte channel. You also need to choose the byte channel 270 handle below. 271 272 config PPC_EARLY_DEBUG_EHV_BC_HANDLE 273 int "Byte channel handle for early console (udbg)" 274 depends on PPC_EARLY_DEBUG_EHV_BC 275 default 0 276 help 277 If you want early console (udbg) output through a byte channel, 278 specify the handle of the byte channel to use. 279 280 For this to work, the byte channel driver must be compiled 281 in-kernel, not as a module. 282 283 Note that only one early console driver can be enabled, so don't 284 enable any others if you enable this one. 285 286 If the number you specify is not a valid byte channel handle, then 287 there simply will be no early console output. This is true also 288 if you don't boot under a hypervisor at all. 289 290 config GOLDFISH_TTY 291 tristate "Goldfish TTY Driver" 292 depends on GOLDFISH 293 select SERIAL_CORE 294 select SERIAL_CORE_CONSOLE 295 help 296 Console and system TTY driver for the Goldfish virtual platform. 297 298 config GOLDFISH_TTY_EARLY_CONSOLE 299 bool 300 default y if GOLDFISH_TTY=y 301 select SERIAL_EARLYCON 302 303 config IPWIRELESS 304 tristate "IPWireless 3G UMTS PCMCIA card support" 305 depends on PCMCIA && NETDEVICES 306 select PPP 307 help 308 This is a driver for 3G UMTS PCMCIA card from IPWireless company. In 309 some countries (for example Czech Republic, T-Mobile ISP) this card 310 is shipped for service called UMTS 4G. 311 312 config N_GSM 313 tristate "GSM MUX line discipline support (EXPERIMENTAL)" 314 depends on NET 315 help 316 This line discipline provides support for the GSM MUX protocol and 317 presents the mux as a set of 61 individual tty devices. 318 319 config NOZOMI 320 tristate "HSDPA Broadband Wireless Data Card - Globe Trotter" 321 depends on PCI 322 help 323 If you have a HSDPA driver Broadband Wireless Data Card - 324 Globe Trotter PCMCIA card, say Y here. 325 326 To compile this driver as a module, choose M here, the module 327 will be called nozomi. 328 329 config MIPS_EJTAG_FDC_TTY 330 bool "MIPS EJTAG Fast Debug Channel TTY" 331 depends on MIPS_CDMM 332 help 333 This enables a TTY and console on the MIPS EJTAG Fast Debug Channels, 334 if they are present. This can be useful when working with an EJTAG 335 probe which supports it, to get console output and a login prompt via 336 EJTAG without needing to connect a serial cable. 337 338 TTY devices are named e.g. ttyFDC3c2 (for FDC channel 2 of the FDC on 339 CPU3). 340 341 The console can be enabled with console=fdc1 (for FDC channel 1 on all 342 CPUs). Do not use the console unless there is a debug probe attached 343 to drain the FDC TX FIFO. 344 345 If unsure, say N. 346 347 config MIPS_EJTAG_FDC_EARLYCON 348 bool "Early FDC console" 349 depends on MIPS_EJTAG_FDC_TTY 350 help 351 This registers a console on FDC channel 1 very early during boot (from 352 MIPS arch code). This is useful for bring-up and debugging early boot 353 issues. 354 355 Do not enable unless there is a debug probe attached to drain the FDC 356 TX FIFO. 357 358 If unsure, say N. 359 360 config MIPS_EJTAG_FDC_KGDB 361 bool "Use KGDB over an FDC channel" 362 depends on MIPS_EJTAG_FDC_TTY && KGDB 363 default y 364 help 365 This enables the use of KGDB over an FDC channel, allowing KGDB to be 366 used remotely or when a serial port isn't available. 367 368 config MIPS_EJTAG_FDC_KGDB_CHAN 369 int "KGDB FDC channel" 370 depends on MIPS_EJTAG_FDC_KGDB 371 range 2 15 372 default 3 373 help 374 FDC channel number to use for KGDB. 375 376 config NULL_TTY 377 tristate "NULL TTY driver" 378 help 379 Say Y here if you want a NULL TTY which simply discards messages. 380 381 This is useful to allow userspace applications which expect a console 382 device to work without modifications even when no console is 383 available or desired. 384 385 In order to use this driver, you should redirect the console to this 386 TTY, or boot the kernel with console=ttynull. 387 388 If unsure, say N. 389 390 config VCC 391 tristate "Sun Virtual Console Concentrator" 392 depends on SUN_LDOMS 393 help 394 Support for Sun logical domain consoles. 395 396 source "drivers/tty/hvc/Kconfig" 397 398 config RPMSG_TTY 399 tristate "RPMSG tty driver" 400 depends on RPMSG 401 help 402 Say y here to export rpmsg endpoints as tty devices, usually found 403 in /dev/ttyRPMSGx. 404 This makes it possible for user-space programs to send and receive 405 rpmsg messages as a standard tty protocol. 406 407 To compile this driver as a module, choose M here: the module will be 408 called rpmsg_tty. 409 410 endif # TTY 411 412 source "drivers/tty/serdev/Kconfig" 413