xref: /openbmc/linux/drivers/tty/Kconfig (revision e7f127b2)
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 LDISC_AUTOLOAD
153	bool "Automatically load TTY Line Disciplines"
154	default y
155	help
156	  Historically the kernel has always automatically loaded any
157	  line discipline that is in a kernel module when a user asks
158	  for it to be loaded with the TIOCSETD ioctl, or through other
159	  means.  This is not always the best thing to do on systems
160	  where you know you will not be using some of the more
161	  "ancient" line disciplines, so prevent the kernel from doing
162	  this unless the request is coming from a process with the
163	  CAP_SYS_MODULE permissions.
164
165	  Say 'Y' here if you trust your userspace users to do the right
166	  thing, or if you have only provided the line disciplines that
167	  you know you will be using, or if you wish to continue to use
168	  the traditional method of on-demand loading of these modules
169	  by any user.
170
171	  This functionality can be changed at runtime with the
172	  dev.tty.ldisc_autoload sysctl, this configuration option will
173	  only set the default value of this functionality.
174
175source "drivers/tty/serial/Kconfig"
176
177config SERIAL_NONSTANDARD
178	bool "Non-standard serial port support"
179	depends on HAS_IOMEM
180	help
181	  Say Y here if you have any non-standard serial boards -- boards
182	  which aren't supported using the standard "dumb" serial driver.
183	  This includes intelligent serial boards such as
184	  Digiboards, etc. These are usually used for systems that need many
185	  serial ports because they serve many terminals or dial-in
186	  connections.
187
188	  Note that the answer to this question won't directly affect the
189	  kernel: saying N will just cause the configurator to skip all
190	  the questions about non-standard serial boards.
191
192	  Most people can say N here.
193
194config MOXA_INTELLIO
195	tristate "Moxa Intellio support"
196	depends on SERIAL_NONSTANDARD && (ISA || EISA || PCI)
197	select FW_LOADER
198	help
199	  Say Y here if you have a Moxa Intellio multiport serial card.
200
201	  To compile this driver as a module, choose M here: the
202	  module will be called moxa.
203
204config MOXA_SMARTIO
205	tristate "Moxa SmartIO support v. 2.0"
206	depends on SERIAL_NONSTANDARD && PCI
207	help
208	  Say Y here if you have a Moxa SmartIO multiport serial card and/or
209	  want to help develop a new version of this driver.
210
211	  This is upgraded (1.9.1) driver from original Moxa drivers with
212	  changes finally resulting in PCI probing.
213
214	  This driver can also be built as a module. The module will be called
215	  mxser. If you want to do that, say M here.
216
217config SYNCLINK_GT
218	tristate "SyncLink GT/AC support"
219	depends on SERIAL_NONSTANDARD && PCI
220	help
221	  Support for SyncLink GT and SyncLink AC families of
222	  synchronous and asynchronous serial adapters
223	  manufactured by Microgate Systems, Ltd. (www.microgate.com)
224
225config N_HDLC
226	tristate "HDLC line discipline support"
227	depends on SERIAL_NONSTANDARD
228	help
229	  Allows synchronous HDLC communications with tty device drivers that
230	  support synchronous HDLC such as the Microgate SyncLink adapter.
231
232	  This driver can be built as a module ( = code which can be
233	  inserted in and removed from the running kernel whenever you want).
234	  The module will be called n_hdlc. If you want to do that, say M
235	  here.
236
237config PPC_EPAPR_HV_BYTECHAN
238	bool "ePAPR hypervisor byte channel driver"
239	depends on PPC
240	select EPAPR_PARAVIRT
241	help
242	  This driver creates /dev entries for each ePAPR hypervisor byte
243	  channel, thereby allowing applications to communicate with byte
244	  channels as if they were serial ports.
245
246config PPC_EARLY_DEBUG_EHV_BC
247	bool "Early console (udbg) support for ePAPR hypervisors"
248	depends on PPC_EPAPR_HV_BYTECHAN=y
249	help
250	  Select this option to enable early console (a.k.a. "udbg") support
251	  via an ePAPR byte channel.  You also need to choose the byte channel
252	  handle below.
253
254config PPC_EARLY_DEBUG_EHV_BC_HANDLE
255	int "Byte channel handle for early console (udbg)"
256	depends on PPC_EARLY_DEBUG_EHV_BC
257	default 0
258	help
259	  If you want early console (udbg) output through a byte channel,
260	  specify the handle of the byte channel to use.
261
262	  For this to work, the byte channel driver must be compiled
263	  in-kernel, not as a module.
264
265	  Note that only one early console driver can be enabled, so don't
266	  enable any others if you enable this one.
267
268	  If the number you specify is not a valid byte channel handle, then
269	  there simply will be no early console output.  This is true also
270	  if you don't boot under a hypervisor at all.
271
272config GOLDFISH_TTY
273	tristate "Goldfish TTY Driver"
274	depends on GOLDFISH
275	select SERIAL_CORE
276	select SERIAL_CORE_CONSOLE
277	help
278	  Console and system TTY driver for the Goldfish virtual platform.
279
280config GOLDFISH_TTY_EARLY_CONSOLE
281	bool
282	default y if GOLDFISH_TTY=y
283	select SERIAL_EARLYCON
284
285config N_GSM
286	tristate "GSM MUX line discipline support (EXPERIMENTAL)"
287	depends on NET
288	help
289	  This line discipline provides support for the GSM MUX protocol and
290	  presents the mux as a set of 61 individual tty devices.
291
292config NOZOMI
293	tristate "HSDPA Broadband Wireless Data Card - Globe Trotter"
294	depends on PCI
295	help
296	  If you have a HSDPA driver Broadband Wireless Data Card -
297	  Globe Trotter PCMCIA card, say Y here.
298
299	  To compile this driver as a module, choose M here, the module
300	  will be called nozomi.
301
302config MIPS_EJTAG_FDC_TTY
303	bool "MIPS EJTAG Fast Debug Channel TTY"
304	depends on MIPS_CDMM
305	help
306	  This enables a TTY and console on the MIPS EJTAG Fast Debug Channels,
307	  if they are present. This can be useful when working with an EJTAG
308	  probe which supports it, to get console output and a login prompt via
309	  EJTAG without needing to connect a serial cable.
310
311	  TTY devices are named e.g. ttyFDC3c2 (for FDC channel 2 of the FDC on
312	  CPU3).
313
314	  The console can be enabled with console=fdc1 (for FDC channel 1 on all
315	  CPUs). Do not use the console unless there is a debug probe attached
316	  to drain the FDC TX FIFO.
317
318	  If unsure, say N.
319
320config MIPS_EJTAG_FDC_EARLYCON
321	bool "Early FDC console"
322	depends on MIPS_EJTAG_FDC_TTY
323	help
324	  This registers a console on FDC channel 1 very early during boot (from
325	  MIPS arch code). This is useful for bring-up and debugging early boot
326	  issues.
327
328	  Do not enable unless there is a debug probe attached to drain the FDC
329	  TX FIFO.
330
331	  If unsure, say N.
332
333config MIPS_EJTAG_FDC_KGDB
334	bool "Use KGDB over an FDC channel"
335	depends on MIPS_EJTAG_FDC_TTY && KGDB
336	default y
337	help
338	  This enables the use of KGDB over an FDC channel, allowing KGDB to be
339	  used remotely or when a serial port isn't available.
340
341config MIPS_EJTAG_FDC_KGDB_CHAN
342	int "KGDB FDC channel"
343	depends on MIPS_EJTAG_FDC_KGDB
344	range 2 15
345	default 3
346	help
347	  FDC channel number to use for KGDB.
348
349config NULL_TTY
350	tristate "NULL TTY driver"
351	help
352	  Say Y here if you want a NULL TTY which simply discards messages.
353
354	  This is useful to allow userspace applications which expect a console
355	  device to work without modifications even when no console is
356	  available or desired.
357
358	  In order to use this driver, you should redirect the console to this
359	  TTY, or boot the kernel with console=ttynull.
360
361	  If unsure, say N.
362
363config VCC
364	tristate "Sun Virtual Console Concentrator"
365	depends on SUN_LDOMS
366	help
367	  Support for Sun logical domain consoles.
368
369source "drivers/tty/hvc/Kconfig"
370
371config RPMSG_TTY
372	tristate "RPMSG tty driver"
373	depends on RPMSG
374	help
375	  Say y here to export rpmsg endpoints as tty devices, usually found
376	  in /dev/ttyRPMSGx.
377	  This makes it possible for user-space programs to send and receive
378	  rpmsg messages as a standard tty protocol.
379
380	  To compile this driver as a module, choose M here: the module will be
381	  called rpmsg_tty.
382
383endif # TTY
384
385source "drivers/tty/serdev/Kconfig"
386