1/* 2 * linux/include/linux/console.h 3 * 4 * Copyright (C) 1993 Hamish Macdonald 5 * 6 * This file is subject to the terms and conditions of the GNU General Public 7 * License. See the file COPYING in the main directory of this archive 8 * for more details. 9 * 10 * Changed: 11 * 10-Mar-94: Arno Griffioen: Conversion for vt100 emulator port from PC LINUX 12 */ 13 14#ifndef _LINUX_CONSOLE_H_ 15#define _LINUX_CONSOLE_H_ 1 16 17#include <linux/atomic.h> 18#include <linux/bits.h> 19#include <linux/rculist.h> 20#include <linux/types.h> 21#include <linux/vesa.h> 22 23struct vc_data; 24struct console_font_op; 25struct console_font; 26struct module; 27struct tty_struct; 28struct notifier_block; 29 30enum con_scroll { 31 SM_UP, 32 SM_DOWN, 33}; 34 35enum vc_intensity; 36 37/** 38 * struct consw - callbacks for consoles 39 * 40 * @owner: the module to get references of when this console is used 41 * @con_startup: set up the console and return its name (like VGA, EGA, ...) 42 * @con_init: initialize the console on @vc. @init is true for the very first 43 * call on this @vc. 44 * @con_deinit: deinitialize the console from @vc. 45 * @con_clear: erase @count characters at [@x, @y] on @vc. @count >= 1. 46 * @con_putc: emit one character with attributes @ca to [@x, @y] on @vc. 47 * (optional -- @con_putcs would be called instead) 48 * @con_putcs: emit @count characters with attributes @s to [@x, @y] on @vc. 49 * @con_cursor: enable/disable cursor depending on @enable 50 * @con_scroll: move lines from @top to @bottom in direction @dir by @lines. 51 * Return true if no generic handling should be done. 52 * Invoked by csi_M and printing to the console. 53 * @con_switch: notifier about the console switch; it is supposed to return 54 * true if a redraw is needed. 55 * @con_blank: blank/unblank the console. The target mode is passed in @blank. 56 * @mode_switch is set if changing from/to text/graphics. The hook 57 * is supposed to return true if a redraw is needed. 58 * @con_font_set: set console @vc font to @font with height @vpitch. @flags can 59 * be %KD_FONT_FLAG_DONT_RECALC. (optional) 60 * @con_font_get: fetch the current font on @vc of height @vpitch into @font. 61 * (optional) 62 * @con_font_default: set default font on @vc. @name can be %NULL or font name 63 * to search for. @font can be filled back. (optional) 64 * @con_resize: resize the @vc console to @width x @height. @from_user is true 65 * when this change comes from the user space. 66 * @con_set_palette: sets the palette of the console @vc to @table (optional) 67 * @con_scrolldelta: the contents of the console should be scrolled by @lines. 68 * Invoked by user. (optional) 69 * @con_set_origin: set origin (see &vc_data::vc_origin) of the @vc. If not 70 * provided or returns false, the origin is set to 71 * @vc->vc_screenbuf. (optional) 72 * @con_save_screen: save screen content into @vc->vc_screenbuf. Called e.g. 73 * upon entering graphics. (optional) 74 * @con_build_attr: build attributes based on @color, @intensity and other 75 * parameters. The result is used for both normal and erase 76 * characters. (optional) 77 * @con_invert_region: invert a region of length @count on @vc starting at @p. 78 * (optional) 79 * @con_debug_enter: prepare the console for the debugger. This includes, but 80 * is not limited to, unblanking the console, loading an 81 * appropriate palette, and allowing debugger generated output. 82 * (optional) 83 * @con_debug_leave: restore the console to its pre-debug state as closely as 84 * possible. (optional) 85 */ 86struct consw { 87 struct module *owner; 88 const char *(*con_startup)(void); 89 void (*con_init)(struct vc_data *vc, bool init); 90 void (*con_deinit)(struct vc_data *vc); 91 void (*con_clear)(struct vc_data *vc, unsigned int y, 92 unsigned int x, unsigned int count); 93 void (*con_putc)(struct vc_data *vc, u16 ca, unsigned int y, 94 unsigned int x); 95 void (*con_putcs)(struct vc_data *vc, const u16 *s, 96 unsigned int count, unsigned int ypos, 97 unsigned int xpos); 98 void (*con_cursor)(struct vc_data *vc, bool enable); 99 bool (*con_scroll)(struct vc_data *vc, unsigned int top, 100 unsigned int bottom, enum con_scroll dir, 101 unsigned int lines); 102 bool (*con_switch)(struct vc_data *vc); 103 bool (*con_blank)(struct vc_data *vc, enum vesa_blank_mode blank, 104 bool mode_switch); 105 int (*con_font_set)(struct vc_data *vc, 106 const struct console_font *font, 107 unsigned int vpitch, unsigned int flags); 108 int (*con_font_get)(struct vc_data *vc, struct console_font *font, 109 unsigned int vpitch); 110 int (*con_font_default)(struct vc_data *vc, 111 struct console_font *font, const char *name); 112 int (*con_resize)(struct vc_data *vc, unsigned int width, 113 unsigned int height, bool from_user); 114 void (*con_set_palette)(struct vc_data *vc, 115 const unsigned char *table); 116 void (*con_scrolldelta)(struct vc_data *vc, int lines); 117 bool (*con_set_origin)(struct vc_data *vc); 118 void (*con_save_screen)(struct vc_data *vc); 119 u8 (*con_build_attr)(struct vc_data *vc, u8 color, 120 enum vc_intensity intensity, 121 bool blink, bool underline, bool reverse, bool italic); 122 void (*con_invert_region)(struct vc_data *vc, u16 *p, int count); 123 void (*con_debug_enter)(struct vc_data *vc); 124 void (*con_debug_leave)(struct vc_data *vc); 125}; 126 127extern const struct consw *conswitchp; 128 129extern const struct consw dummy_con; /* dummy console buffer */ 130extern const struct consw vga_con; /* VGA text console */ 131extern const struct consw newport_con; /* SGI Newport console */ 132 133struct screen_info; 134#ifdef CONFIG_VGA_CONSOLE 135void vgacon_register_screen(struct screen_info *si); 136#else 137static inline void vgacon_register_screen(struct screen_info *si) { } 138#endif 139 140int con_is_bound(const struct consw *csw); 141int do_unregister_con_driver(const struct consw *csw); 142int do_take_over_console(const struct consw *sw, int first, int last, int deflt); 143void give_up_console(const struct consw *sw); 144#ifdef CONFIG_VT 145void con_debug_enter(struct vc_data *vc); 146void con_debug_leave(void); 147#else 148static inline void con_debug_enter(struct vc_data *vc) { } 149static inline void con_debug_leave(void) { } 150#endif 151 152/* 153 * The interface for a console, or any other device that wants to capture 154 * console messages (printer driver?) 155 */ 156 157/** 158 * enum cons_flags - General console flags 159 * @CON_PRINTBUFFER: Used by newly registered consoles to avoid duplicate 160 * output of messages that were already shown by boot 161 * consoles or read by userspace via syslog() syscall. 162 * @CON_CONSDEV: Indicates that the console driver is backing 163 * /dev/console. 164 * @CON_ENABLED: Indicates if a console is allowed to print records. If 165 * false, the console also will not advance to later 166 * records. 167 * @CON_BOOT: Marks the console driver as early console driver which 168 * is used during boot before the real driver becomes 169 * available. It will be automatically unregistered 170 * when the real console driver is registered unless 171 * "keep_bootcon" parameter is used. 172 * @CON_ANYTIME: A misnomed historical flag which tells the core code 173 * that the legacy @console::write callback can be invoked 174 * on a CPU which is marked OFFLINE. That is misleading as 175 * it suggests that there is no contextual limit for 176 * invoking the callback. The original motivation was 177 * readiness of the per-CPU areas. 178 * @CON_BRL: Indicates a braille device which is exempt from 179 * receiving the printk spam for obvious reasons. 180 * @CON_EXTENDED: The console supports the extended output format of 181 * /dev/kmesg which requires a larger output buffer. 182 * @CON_SUSPENDED: Indicates if a console is suspended. If true, the 183 * printing callbacks must not be called. 184 * @CON_NBCON: Console can operate outside of the legacy style console_lock 185 * constraints. 186 */ 187enum cons_flags { 188 CON_PRINTBUFFER = BIT(0), 189 CON_CONSDEV = BIT(1), 190 CON_ENABLED = BIT(2), 191 CON_BOOT = BIT(3), 192 CON_ANYTIME = BIT(4), 193 CON_BRL = BIT(5), 194 CON_EXTENDED = BIT(6), 195 CON_SUSPENDED = BIT(7), 196 CON_NBCON = BIT(8), 197}; 198 199/** 200 * struct nbcon_state - console state for nbcon consoles 201 * @atom: Compound of the state fields for atomic operations 202 * 203 * @req_prio: The priority of a handover request 204 * @prio: The priority of the current owner 205 * @unsafe: Console is busy in a non takeover region 206 * @unsafe_takeover: A hostile takeover in an unsafe state happened in the 207 * past. The console cannot be safe until re-initialized. 208 * @cpu: The CPU on which the owner runs 209 * 210 * To be used for reading and preparing of the value stored in the nbcon 211 * state variable @console::nbcon_state. 212 * 213 * The @prio and @req_prio fields are particularly important to allow 214 * spin-waiting to timeout and give up without the risk of a waiter being 215 * assigned the lock after giving up. 216 */ 217struct nbcon_state { 218 union { 219 unsigned int atom; 220 struct { 221 unsigned int prio : 2; 222 unsigned int req_prio : 2; 223 unsigned int unsafe : 1; 224 unsigned int unsafe_takeover : 1; 225 unsigned int cpu : 24; 226 }; 227 }; 228}; 229 230/* 231 * The nbcon_state struct is used to easily create and interpret values that 232 * are stored in the @console::nbcon_state variable. Ensure this struct stays 233 * within the size boundaries of the atomic variable's underlying type in 234 * order to avoid any accidental truncation. 235 */ 236static_assert(sizeof(struct nbcon_state) <= sizeof(int)); 237 238/** 239 * enum nbcon_prio - console owner priority for nbcon consoles 240 * @NBCON_PRIO_NONE: Unused 241 * @NBCON_PRIO_NORMAL: Normal (non-emergency) usage 242 * @NBCON_PRIO_EMERGENCY: Emergency output (WARN/OOPS...) 243 * @NBCON_PRIO_PANIC: Panic output 244 * @NBCON_PRIO_MAX: The number of priority levels 245 * 246 * A higher priority context can takeover the console when it is 247 * in the safe state. The final attempt to flush consoles in panic() 248 * can be allowed to do so even in an unsafe state (Hope and pray). 249 */ 250enum nbcon_prio { 251 NBCON_PRIO_NONE = 0, 252 NBCON_PRIO_NORMAL, 253 NBCON_PRIO_EMERGENCY, 254 NBCON_PRIO_PANIC, 255 NBCON_PRIO_MAX, 256}; 257 258struct console; 259struct printk_buffers; 260 261/** 262 * struct nbcon_context - Context for console acquire/release 263 * @console: The associated console 264 * @spinwait_max_us: Limit for spin-wait acquire 265 * @prio: Priority of the context 266 * @allow_unsafe_takeover: Allow performing takeover even if unsafe. Can 267 * be used only with NBCON_PRIO_PANIC @prio. It 268 * might cause a system freeze when the console 269 * is used later. 270 * @backlog: Ringbuffer has pending records 271 * @pbufs: Pointer to the text buffer for this context 272 * @seq: The sequence number to print for this context 273 */ 274struct nbcon_context { 275 /* members set by caller */ 276 struct console *console; 277 unsigned int spinwait_max_us; 278 enum nbcon_prio prio; 279 unsigned int allow_unsafe_takeover : 1; 280 281 /* members set by emit */ 282 unsigned int backlog : 1; 283 284 /* members set by acquire */ 285 struct printk_buffers *pbufs; 286 u64 seq; 287}; 288 289/** 290 * struct nbcon_write_context - Context handed to the nbcon write callbacks 291 * @ctxt: The core console context 292 * @outbuf: Pointer to the text buffer for output 293 * @len: Length to write 294 * @unsafe_takeover: If a hostile takeover in an unsafe state has occurred 295 */ 296struct nbcon_write_context { 297 struct nbcon_context __private ctxt; 298 char *outbuf; 299 unsigned int len; 300 bool unsafe_takeover; 301}; 302 303/** 304 * struct console - The console descriptor structure 305 * @name: The name of the console driver 306 * @write: Write callback to output messages (Optional) 307 * @read: Read callback for console input (Optional) 308 * @device: The underlying TTY device driver (Optional) 309 * @unblank: Callback to unblank the console (Optional) 310 * @setup: Callback for initializing the console (Optional) 311 * @exit: Callback for teardown of the console (Optional) 312 * @match: Callback for matching a console (Optional) 313 * @flags: Console flags. See enum cons_flags 314 * @index: Console index, e.g. port number 315 * @cflag: TTY control mode flags 316 * @ispeed: TTY input speed 317 * @ospeed: TTY output speed 318 * @seq: Sequence number of the next ringbuffer record to print 319 * @dropped: Number of unreported dropped ringbuffer records 320 * @data: Driver private data 321 * @node: hlist node for the console list 322 * 323 * @write_atomic: Write callback for atomic context 324 * @nbcon_state: State for nbcon consoles 325 * @nbcon_seq: Sequence number of the next record for nbcon to print 326 * @pbufs: Pointer to nbcon private buffer 327 */ 328struct console { 329 char name[16]; 330 void (*write)(struct console *co, const char *s, unsigned int count); 331 int (*read)(struct console *co, char *s, unsigned int count); 332 struct tty_driver *(*device)(struct console *co, int *index); 333 void (*unblank)(void); 334 int (*setup)(struct console *co, char *options); 335 int (*exit)(struct console *co); 336 int (*match)(struct console *co, char *name, int idx, char *options); 337 short flags; 338 short index; 339 int cflag; 340 uint ispeed; 341 uint ospeed; 342 u64 seq; 343 unsigned long dropped; 344 void *data; 345 struct hlist_node node; 346 347 /* nbcon console specific members */ 348 bool (*write_atomic)(struct console *con, 349 struct nbcon_write_context *wctxt); 350 atomic_t __private nbcon_state; 351 atomic_long_t __private nbcon_seq; 352 struct printk_buffers *pbufs; 353}; 354 355#ifdef CONFIG_LOCKDEP 356extern void lockdep_assert_console_list_lock_held(void); 357#else 358static inline void lockdep_assert_console_list_lock_held(void) 359{ 360} 361#endif 362 363#ifdef CONFIG_DEBUG_LOCK_ALLOC 364extern bool console_srcu_read_lock_is_held(void); 365#else 366static inline bool console_srcu_read_lock_is_held(void) 367{ 368 return 1; 369} 370#endif 371 372extern int console_srcu_read_lock(void); 373extern void console_srcu_read_unlock(int cookie); 374 375extern void console_list_lock(void) __acquires(console_mutex); 376extern void console_list_unlock(void) __releases(console_mutex); 377 378extern struct hlist_head console_list; 379 380/** 381 * console_srcu_read_flags - Locklessly read the console flags 382 * @con: struct console pointer of console to read flags from 383 * 384 * This function provides the necessary READ_ONCE() and data_race() 385 * notation for locklessly reading the console flags. The READ_ONCE() 386 * in this function matches the WRITE_ONCE() when @flags are modified 387 * for registered consoles with console_srcu_write_flags(). 388 * 389 * Only use this function to read console flags when locklessly 390 * iterating the console list via srcu. 391 * 392 * Context: Any context. 393 */ 394static inline short console_srcu_read_flags(const struct console *con) 395{ 396 WARN_ON_ONCE(!console_srcu_read_lock_is_held()); 397 398 /* 399 * Locklessly reading console->flags provides a consistent 400 * read value because there is at most one CPU modifying 401 * console->flags and that CPU is using only read-modify-write 402 * operations to do so. 403 */ 404 return data_race(READ_ONCE(con->flags)); 405} 406 407/** 408 * console_srcu_write_flags - Write flags for a registered console 409 * @con: struct console pointer of console to write flags to 410 * @flags: new flags value to write 411 * 412 * Only use this function to write flags for registered consoles. It 413 * requires holding the console_list_lock. 414 * 415 * Context: Any context. 416 */ 417static inline void console_srcu_write_flags(struct console *con, short flags) 418{ 419 lockdep_assert_console_list_lock_held(); 420 421 /* This matches the READ_ONCE() in console_srcu_read_flags(). */ 422 WRITE_ONCE(con->flags, flags); 423} 424 425/* Variant of console_is_registered() when the console_list_lock is held. */ 426static inline bool console_is_registered_locked(const struct console *con) 427{ 428 lockdep_assert_console_list_lock_held(); 429 return !hlist_unhashed(&con->node); 430} 431 432/* 433 * console_is_registered - Check if the console is registered 434 * @con: struct console pointer of console to check 435 * 436 * Context: Process context. May sleep while acquiring console list lock. 437 * Return: true if the console is in the console list, otherwise false. 438 * 439 * If false is returned for a console that was previously registered, it 440 * can be assumed that the console's unregistration is fully completed, 441 * including the exit() callback after console list removal. 442 */ 443static inline bool console_is_registered(const struct console *con) 444{ 445 bool ret; 446 447 console_list_lock(); 448 ret = console_is_registered_locked(con); 449 console_list_unlock(); 450 return ret; 451} 452 453/** 454 * for_each_console_srcu() - Iterator over registered consoles 455 * @con: struct console pointer used as loop cursor 456 * 457 * Although SRCU guarantees the console list will be consistent, the 458 * struct console fields may be updated by other CPUs while iterating. 459 * 460 * Requires console_srcu_read_lock to be held. Can be invoked from 461 * any context. 462 */ 463#define for_each_console_srcu(con) \ 464 hlist_for_each_entry_srcu(con, &console_list, node, \ 465 console_srcu_read_lock_is_held()) 466 467/** 468 * for_each_console() - Iterator over registered consoles 469 * @con: struct console pointer used as loop cursor 470 * 471 * The console list and the &console.flags are immutable while iterating. 472 * 473 * Requires console_list_lock to be held. 474 */ 475#define for_each_console(con) \ 476 lockdep_assert_console_list_lock_held(); \ 477 hlist_for_each_entry(con, &console_list, node) 478 479#ifdef CONFIG_PRINTK 480extern bool nbcon_can_proceed(struct nbcon_write_context *wctxt); 481extern bool nbcon_enter_unsafe(struct nbcon_write_context *wctxt); 482extern bool nbcon_exit_unsafe(struct nbcon_write_context *wctxt); 483#else 484static inline bool nbcon_can_proceed(struct nbcon_write_context *wctxt) { return false; } 485static inline bool nbcon_enter_unsafe(struct nbcon_write_context *wctxt) { return false; } 486static inline bool nbcon_exit_unsafe(struct nbcon_write_context *wctxt) { return false; } 487#endif 488 489extern int console_set_on_cmdline; 490extern struct console *early_console; 491 492enum con_flush_mode { 493 CONSOLE_FLUSH_PENDING, 494 CONSOLE_REPLAY_ALL, 495}; 496 497extern int add_preferred_console(const char *name, const short idx, char *options); 498extern void console_force_preferred_locked(struct console *con); 499extern void register_console(struct console *); 500extern int unregister_console(struct console *); 501extern void console_lock(void); 502extern int console_trylock(void); 503extern void console_unlock(void); 504extern void console_conditional_schedule(void); 505extern void console_unblank(void); 506extern void console_flush_on_panic(enum con_flush_mode mode); 507extern struct tty_driver *console_device(int *); 508extern void console_stop(struct console *); 509extern void console_start(struct console *); 510extern int is_console_locked(void); 511extern int braille_register_console(struct console *, int index, 512 char *console_options, char *braille_options); 513extern int braille_unregister_console(struct console *); 514#ifdef CONFIG_TTY 515extern void console_sysfs_notify(void); 516#else 517static inline void console_sysfs_notify(void) 518{ } 519#endif 520extern bool console_suspend_enabled; 521 522/* Suspend and resume console messages over PM events */ 523extern void suspend_console(void); 524extern void resume_console(void); 525 526int mda_console_init(void); 527 528void vcs_make_sysfs(int index); 529void vcs_remove_sysfs(int index); 530 531/* Some debug stub to catch some of the obvious races in the VT code */ 532#define WARN_CONSOLE_UNLOCKED() \ 533 WARN_ON(!atomic_read(&ignore_console_lock_warning) && \ 534 !is_console_locked() && !oops_in_progress) 535/* 536 * Increment ignore_console_lock_warning if you need to quiet 537 * WARN_CONSOLE_UNLOCKED() for debugging purposes. 538 */ 539extern atomic_t ignore_console_lock_warning; 540 541extern void console_init(void); 542 543/* For deferred console takeover */ 544void dummycon_register_output_notifier(struct notifier_block *nb); 545void dummycon_unregister_output_notifier(struct notifier_block *nb); 546 547#endif /* _LINUX_CONSOLE_H */ 548