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