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 depends on BROKEN 243 help 244 Support for SyncLink GT and SyncLink AC families of 245 synchronous and asynchronous serial adapters 246 manufactured by Microgate Systems, Ltd. (www.microgate.com) 247 248config N_HDLC 249 tristate "HDLC line discipline support" 250 depends on SERIAL_NONSTANDARD 251 help 252 Allows synchronous HDLC communications with tty device drivers that 253 support synchronous HDLC such as the Microgate SyncLink adapter. 254 255 This driver can be built as a module ( = code which can be 256 inserted in and removed from the running kernel whenever you want). 257 The module will be called n_hdlc. If you want to do that, say M 258 here. 259 260config PPC_EPAPR_HV_BYTECHAN 261 bool "ePAPR hypervisor byte channel driver" 262 depends on PPC 263 select EPAPR_PARAVIRT 264 help 265 This driver creates /dev entries for each ePAPR hypervisor byte 266 channel, thereby allowing applications to communicate with byte 267 channels as if they were serial ports. 268 269config PPC_EARLY_DEBUG_EHV_BC 270 bool "Early console (udbg) support for ePAPR hypervisors" 271 depends on PPC_EPAPR_HV_BYTECHAN=y 272 help 273 Select this option to enable early console (a.k.a. "udbg") support 274 via an ePAPR byte channel. You also need to choose the byte channel 275 handle below. 276 277config PPC_EARLY_DEBUG_EHV_BC_HANDLE 278 int "Byte channel handle for early console (udbg)" 279 depends on PPC_EARLY_DEBUG_EHV_BC 280 default 0 281 help 282 If you want early console (udbg) output through a byte channel, 283 specify the handle of the byte channel to use. 284 285 For this to work, the byte channel driver must be compiled 286 in-kernel, not as a module. 287 288 Note that only one early console driver can be enabled, so don't 289 enable any others if you enable this one. 290 291 If the number you specify is not a valid byte channel handle, then 292 there simply will be no early console output. This is true also 293 if you don't boot under a hypervisor at all. 294 295config GOLDFISH_TTY 296 tristate "Goldfish TTY Driver" 297 depends on GOLDFISH 298 select SERIAL_CORE 299 select SERIAL_CORE_CONSOLE 300 help 301 Console and system TTY driver for the Goldfish virtual platform. 302 303config GOLDFISH_TTY_EARLY_CONSOLE 304 bool 305 default y if GOLDFISH_TTY=y 306 select SERIAL_EARLYCON 307 308config IPWIRELESS 309 tristate "IPWireless 3G UMTS PCMCIA card support" 310 depends on PCMCIA && NETDEVICES 311 select PPP 312 help 313 This is a driver for 3G UMTS PCMCIA card from IPWireless company. In 314 some countries (for example Czech Republic, T-Mobile ISP) this card 315 is shipped for service called UMTS 4G. 316 317config N_GSM 318 tristate "GSM MUX line discipline support (EXPERIMENTAL)" 319 depends on NET 320 help 321 This line discipline provides support for the GSM MUX protocol and 322 presents the mux as a set of 61 individual tty devices. 323 324config NOZOMI 325 tristate "HSDPA Broadband Wireless Data Card - Globe Trotter" 326 depends on PCI 327 help 328 If you have a HSDPA driver Broadband Wireless Data Card - 329 Globe Trotter PCMCIA card, say Y here. 330 331 To compile this driver as a module, choose M here, the module 332 will be called nozomi. 333 334config MIPS_EJTAG_FDC_TTY 335 bool "MIPS EJTAG Fast Debug Channel TTY" 336 depends on MIPS_CDMM 337 help 338 This enables a TTY and console on the MIPS EJTAG Fast Debug Channels, 339 if they are present. This can be useful when working with an EJTAG 340 probe which supports it, to get console output and a login prompt via 341 EJTAG without needing to connect a serial cable. 342 343 TTY devices are named e.g. ttyFDC3c2 (for FDC channel 2 of the FDC on 344 CPU3). 345 346 The console can be enabled with console=fdc1 (for FDC channel 1 on all 347 CPUs). Do not use the console unless there is a debug probe attached 348 to drain the FDC TX FIFO. 349 350 If unsure, say N. 351 352config MIPS_EJTAG_FDC_EARLYCON 353 bool "Early FDC console" 354 depends on MIPS_EJTAG_FDC_TTY 355 help 356 This registers a console on FDC channel 1 very early during boot (from 357 MIPS arch code). This is useful for bring-up and debugging early boot 358 issues. 359 360 Do not enable unless there is a debug probe attached to drain the FDC 361 TX FIFO. 362 363 If unsure, say N. 364 365config MIPS_EJTAG_FDC_KGDB 366 bool "Use KGDB over an FDC channel" 367 depends on MIPS_EJTAG_FDC_TTY && KGDB 368 default y 369 help 370 This enables the use of KGDB over an FDC channel, allowing KGDB to be 371 used remotely or when a serial port isn't available. 372 373config MIPS_EJTAG_FDC_KGDB_CHAN 374 int "KGDB FDC channel" 375 depends on MIPS_EJTAG_FDC_KGDB 376 range 2 15 377 default 3 378 help 379 FDC channel number to use for KGDB. 380 381config NULL_TTY 382 tristate "NULL TTY driver" 383 help 384 Say Y here if you want a NULL TTY which simply discards messages. 385 386 This is useful to allow userspace applications which expect a console 387 device to work without modifications even when no console is 388 available or desired. 389 390 In order to use this driver, you should redirect the console to this 391 TTY, or boot the kernel with console=ttynull. 392 393 If unsure, say N. 394 395config VCC 396 tristate "Sun Virtual Console Concentrator" 397 depends on SUN_LDOMS 398 help 399 Support for Sun logical domain consoles. 400 401source "drivers/tty/hvc/Kconfig" 402 403config RPMSG_TTY 404 tristate "RPMSG tty driver" 405 depends on RPMSG 406 help 407 Say y here to export rpmsg endpoints as tty devices, usually found 408 in /dev/ttyRPMSGx. 409 This makes it possible for user-space programs to send and receive 410 rpmsg messages as a standard tty protocol. 411 412 To compile this driver as a module, choose M here: the module will be 413 called rpmsg_tty. 414 415endif # TTY 416 417source "drivers/tty/serdev/Kconfig" 418