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