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/irq_work.h>
20 #include <linux/rculist.h>
21 #include <linux/rcuwait.h>
22 #include <linux/types.h>
23 #include <linux/vesa.h>
24
25 struct vc_data;
26 struct console_font_op;
27 struct console_font;
28 struct module;
29 struct tty_struct;
30 struct notifier_block;
31
32 enum con_scroll {
33 SM_UP,
34 SM_DOWN,
35 };
36
37 enum vc_intensity;
38
39 /**
40 * struct consw - callbacks for consoles
41 *
42 * @owner: the module to get references of when this console is used
43 * @con_startup: set up the console and return its name (like VGA, EGA, ...)
44 * @con_init: initialize the console on @vc. @init is true for the very first
45 * call on this @vc.
46 * @con_deinit: deinitialize the console from @vc.
47 * @con_clear: erase @count characters at [@x, @y] on @vc. @count >= 1.
48 * @con_putc: emit one character with attributes @ca to [@x, @y] on @vc.
49 * (optional -- @con_putcs would be called instead)
50 * @con_putcs: emit @count characters with attributes @s to [@x, @y] on @vc.
51 * @con_cursor: enable/disable cursor depending on @enable
52 * @con_scroll: move lines from @top to @bottom in direction @dir by @lines.
53 * Return true if no generic handling should be done.
54 * Invoked by csi_M and printing to the console.
55 * @con_switch: notifier about the console switch; it is supposed to return
56 * true if a redraw is needed.
57 * @con_blank: blank/unblank the console. The target mode is passed in @blank.
58 * @mode_switch is set if changing from/to text/graphics. The hook
59 * is supposed to return true if a redraw is needed.
60 * @con_font_set: set console @vc font to @font with height @vpitch. @flags can
61 * be %KD_FONT_FLAG_DONT_RECALC. (optional)
62 * @con_font_get: fetch the current font on @vc of height @vpitch into @font.
63 * (optional)
64 * @con_font_default: set default font on @vc. @name can be %NULL or font name
65 * to search for. @font can be filled back. (optional)
66 * @con_resize: resize the @vc console to @width x @height. @from_user is true
67 * when this change comes from the user space.
68 * @con_set_palette: sets the palette of the console @vc to @table (optional)
69 * @con_scrolldelta: the contents of the console should be scrolled by @lines.
70 * Invoked by user. (optional)
71 * @con_set_origin: set origin (see &vc_data::vc_origin) of the @vc. If not
72 * provided or returns false, the origin is set to
73 * @vc->vc_screenbuf. (optional)
74 * @con_save_screen: save screen content into @vc->vc_screenbuf. Called e.g.
75 * upon entering graphics. (optional)
76 * @con_build_attr: build attributes based on @color, @intensity and other
77 * parameters. The result is used for both normal and erase
78 * characters. (optional)
79 * @con_invert_region: invert a region of length @count on @vc starting at @p.
80 * (optional)
81 * @con_debug_enter: prepare the console for the debugger. This includes, but
82 * is not limited to, unblanking the console, loading an
83 * appropriate palette, and allowing debugger generated output.
84 * (optional)
85 * @con_debug_leave: restore the console to its pre-debug state as closely as
86 * possible. (optional)
87 */
88 struct consw {
89 struct module *owner;
90 const char *(*con_startup)(void);
91 void (*con_init)(struct vc_data *vc, bool init);
92 void (*con_deinit)(struct vc_data *vc);
93 void (*con_clear)(struct vc_data *vc, unsigned int y,
94 unsigned int x, unsigned int count);
95 void (*con_putc)(struct vc_data *vc, u16 ca, unsigned int y,
96 unsigned int x);
97 void (*con_putcs)(struct vc_data *vc, const u16 *s,
98 unsigned int count, unsigned int ypos,
99 unsigned int xpos);
100 void (*con_cursor)(struct vc_data *vc, bool enable);
101 bool (*con_scroll)(struct vc_data *vc, unsigned int top,
102 unsigned int bottom, enum con_scroll dir,
103 unsigned int lines);
104 bool (*con_switch)(struct vc_data *vc);
105 bool (*con_blank)(struct vc_data *vc, enum vesa_blank_mode blank,
106 bool mode_switch);
107 int (*con_font_set)(struct vc_data *vc,
108 const struct console_font *font,
109 unsigned int vpitch, unsigned int flags);
110 int (*con_font_get)(struct vc_data *vc, struct console_font *font,
111 unsigned int vpitch);
112 int (*con_font_default)(struct vc_data *vc,
113 struct console_font *font, const char *name);
114 int (*con_resize)(struct vc_data *vc, unsigned int width,
115 unsigned int height, bool from_user);
116 void (*con_set_palette)(struct vc_data *vc,
117 const unsigned char *table);
118 void (*con_scrolldelta)(struct vc_data *vc, int lines);
119 bool (*con_set_origin)(struct vc_data *vc);
120 void (*con_save_screen)(struct vc_data *vc);
121 u8 (*con_build_attr)(struct vc_data *vc, u8 color,
122 enum vc_intensity intensity,
123 bool blink, bool underline, bool reverse, bool italic);
124 void (*con_invert_region)(struct vc_data *vc, u16 *p, int count);
125 void (*con_debug_enter)(struct vc_data *vc);
126 void (*con_debug_leave)(struct vc_data *vc);
127 };
128
129 extern const struct consw *conswitchp;
130
131 extern const struct consw dummy_con; /* dummy console buffer */
132 extern const struct consw vga_con; /* VGA text console */
133 extern const struct consw newport_con; /* SGI Newport console */
134
135 struct screen_info;
136 #ifdef CONFIG_VGA_CONSOLE
137 void vgacon_register_screen(struct screen_info *si);
138 #else
vgacon_register_screen(struct screen_info * si)139 static inline void vgacon_register_screen(struct screen_info *si) { }
140 #endif
141
142 int con_is_bound(const struct consw *csw);
143 int do_unregister_con_driver(const struct consw *csw);
144 int do_take_over_console(const struct consw *sw, int first, int last, int deflt);
145 void give_up_console(const struct consw *sw);
146 #ifdef CONFIG_VT
147 void con_debug_enter(struct vc_data *vc);
148 void con_debug_leave(void);
149 #else
con_debug_enter(struct vc_data * vc)150 static inline void con_debug_enter(struct vc_data *vc) { }
con_debug_leave(void)151 static inline void con_debug_leave(void) { }
152 #endif
153
154 /*
155 * The interface for a console, or any other device that wants to capture
156 * console messages (printer driver?)
157 */
158
159 /**
160 * enum cons_flags - General console flags
161 * @CON_PRINTBUFFER: Used by newly registered consoles to avoid duplicate
162 * output of messages that were already shown by boot
163 * consoles or read by userspace via syslog() syscall.
164 * @CON_CONSDEV: Indicates that the console driver is backing
165 * /dev/console.
166 * @CON_ENABLED: Indicates if a console is allowed to print records. If
167 * false, the console also will not advance to later
168 * records.
169 * @CON_BOOT: Marks the console driver as early console driver which
170 * is used during boot before the real driver becomes
171 * available. It will be automatically unregistered
172 * when the real console driver is registered unless
173 * "keep_bootcon" parameter is used.
174 * @CON_ANYTIME: A misnomed historical flag which tells the core code
175 * that the legacy @console::write callback can be invoked
176 * on a CPU which is marked OFFLINE. That is misleading as
177 * it suggests that there is no contextual limit for
178 * invoking the callback. The original motivation was
179 * readiness of the per-CPU areas.
180 * @CON_BRL: Indicates a braille device which is exempt from
181 * receiving the printk spam for obvious reasons.
182 * @CON_EXTENDED: The console supports the extended output format of
183 * /dev/kmesg which requires a larger output buffer.
184 * @CON_SUSPENDED: Indicates if a console is suspended. If true, the
185 * printing callbacks must not be called.
186 * @CON_NBCON: Console can operate outside of the legacy style console_lock
187 * constraints.
188 */
189 enum cons_flags {
190 CON_PRINTBUFFER = BIT(0),
191 CON_CONSDEV = BIT(1),
192 CON_ENABLED = BIT(2),
193 CON_BOOT = BIT(3),
194 CON_ANYTIME = BIT(4),
195 CON_BRL = BIT(5),
196 CON_EXTENDED = BIT(6),
197 CON_SUSPENDED = BIT(7),
198 CON_NBCON = BIT(8),
199 };
200
201 /**
202 * struct nbcon_state - console state for nbcon consoles
203 * @atom: Compound of the state fields for atomic operations
204 *
205 * @req_prio: The priority of a handover request
206 * @prio: The priority of the current owner
207 * @unsafe: Console is busy in a non takeover region
208 * @unsafe_takeover: A hostile takeover in an unsafe state happened in the
209 * past. The console cannot be safe until re-initialized.
210 * @cpu: The CPU on which the owner runs
211 *
212 * To be used for reading and preparing of the value stored in the nbcon
213 * state variable @console::nbcon_state.
214 *
215 * The @prio and @req_prio fields are particularly important to allow
216 * spin-waiting to timeout and give up without the risk of a waiter being
217 * assigned the lock after giving up.
218 */
219 struct nbcon_state {
220 union {
221 unsigned int atom;
222 struct {
223 unsigned int prio : 2;
224 unsigned int req_prio : 2;
225 unsigned int unsafe : 1;
226 unsigned int unsafe_takeover : 1;
227 unsigned int cpu : 24;
228 };
229 };
230 };
231
232 /*
233 * The nbcon_state struct is used to easily create and interpret values that
234 * are stored in the @console::nbcon_state variable. Ensure this struct stays
235 * within the size boundaries of the atomic variable's underlying type in
236 * order to avoid any accidental truncation.
237 */
238 static_assert(sizeof(struct nbcon_state) <= sizeof(int));
239
240 /**
241 * enum nbcon_prio - console owner priority for nbcon consoles
242 * @NBCON_PRIO_NONE: Unused
243 * @NBCON_PRIO_NORMAL: Normal (non-emergency) usage
244 * @NBCON_PRIO_EMERGENCY: Emergency output (WARN/OOPS...)
245 * @NBCON_PRIO_PANIC: Panic output
246 * @NBCON_PRIO_MAX: The number of priority levels
247 *
248 * A higher priority context can takeover the console when it is
249 * in the safe state. The final attempt to flush consoles in panic()
250 * can be allowed to do so even in an unsafe state (Hope and pray).
251 */
252 enum nbcon_prio {
253 NBCON_PRIO_NONE = 0,
254 NBCON_PRIO_NORMAL,
255 NBCON_PRIO_EMERGENCY,
256 NBCON_PRIO_PANIC,
257 NBCON_PRIO_MAX,
258 };
259
260 struct console;
261 struct printk_buffers;
262
263 /**
264 * struct nbcon_context - Context for console acquire/release
265 * @console: The associated console
266 * @spinwait_max_us: Limit for spin-wait acquire
267 * @prio: Priority of the context
268 * @allow_unsafe_takeover: Allow performing takeover even if unsafe. Can
269 * be used only with NBCON_PRIO_PANIC @prio. It
270 * might cause a system freeze when the console
271 * is used later.
272 * @backlog: Ringbuffer has pending records
273 * @pbufs: Pointer to the text buffer for this context
274 * @seq: The sequence number to print for this context
275 */
276 struct nbcon_context {
277 /* members set by caller */
278 struct console *console;
279 unsigned int spinwait_max_us;
280 enum nbcon_prio prio;
281 unsigned int allow_unsafe_takeover : 1;
282
283 /* members set by emit */
284 unsigned int backlog : 1;
285
286 /* members set by acquire */
287 struct printk_buffers *pbufs;
288 u64 seq;
289 };
290
291 /**
292 * struct nbcon_write_context - Context handed to the nbcon write callbacks
293 * @ctxt: The core console context
294 * @outbuf: Pointer to the text buffer for output
295 * @len: Length to write
296 * @unsafe_takeover: If a hostile takeover in an unsafe state has occurred
297 */
298 struct nbcon_write_context {
299 struct nbcon_context __private ctxt;
300 char *outbuf;
301 unsigned int len;
302 bool unsafe_takeover;
303 };
304
305 /**
306 * struct console - The console descriptor structure
307 * @name: The name of the console driver
308 * @write: Legacy write callback to output messages (Optional)
309 * @read: Read callback for console input (Optional)
310 * @device: The underlying TTY device driver (Optional)
311 * @unblank: Callback to unblank the console (Optional)
312 * @setup: Callback for initializing the console (Optional)
313 * @exit: Callback for teardown of the console (Optional)
314 * @match: Callback for matching a console (Optional)
315 * @flags: Console flags. See enum cons_flags
316 * @index: Console index, e.g. port number
317 * @cflag: TTY control mode flags
318 * @ispeed: TTY input speed
319 * @ospeed: TTY output speed
320 * @seq: Sequence number of the next ringbuffer record to print
321 * @dropped: Number of unreported dropped ringbuffer records
322 * @data: Driver private data
323 * @node: hlist node for the console list
324 *
325 * @nbcon_state: State for nbcon consoles
326 * @nbcon_seq: Sequence number of the next record for nbcon to print
327 * @nbcon_device_ctxt: Context available for non-printing operations
328 * @nbcon_prev_seq: Seq num the previous nbcon owner was assigned to print
329 * @pbufs: Pointer to nbcon private buffer
330 * @kthread: Printer kthread for this console
331 * @rcuwait: RCU-safe wait object for @kthread waking
332 * @irq_work: Defer @kthread waking to IRQ work context
333 */
334 struct console {
335 char name[16];
336 void (*write)(struct console *co, const char *s, unsigned int count);
337 int (*read)(struct console *co, char *s, unsigned int count);
338 struct tty_driver *(*device)(struct console *co, int *index);
339 void (*unblank)(void);
340 int (*setup)(struct console *co, char *options);
341 int (*exit)(struct console *co);
342 int (*match)(struct console *co, char *name, int idx, char *options);
343 short flags;
344 short index;
345 int cflag;
346 uint ispeed;
347 uint ospeed;
348 u64 seq;
349 unsigned long dropped;
350 void *data;
351 struct hlist_node node;
352
353 /* nbcon console specific members */
354
355 /**
356 * @write_atomic:
357 *
358 * NBCON callback to write out text in any context. (Optional)
359 *
360 * This callback is called with the console already acquired. However,
361 * a higher priority context is allowed to take it over by default.
362 *
363 * The callback must call nbcon_enter_unsafe() and nbcon_exit_unsafe()
364 * around any code where the takeover is not safe, for example, when
365 * manipulating the serial port registers.
366 *
367 * nbcon_enter_unsafe() will fail if the context has lost the console
368 * ownership in the meantime. In this case, the callback is no longer
369 * allowed to go forward. It must back out immediately and carefully.
370 * The buffer content is also no longer trusted since it no longer
371 * belongs to the context.
372 *
373 * The callback should allow the takeover whenever it is safe. It
374 * increases the chance to see messages when the system is in trouble.
375 * If the driver must reacquire ownership in order to finalize or
376 * revert hardware changes, nbcon_reacquire_nobuf() can be used.
377 * However, on reacquire the buffer content is no longer available. A
378 * reacquire cannot be used to resume printing.
379 *
380 * The callback can be called from any context (including NMI).
381 * Therefore it must avoid usage of any locking and instead rely
382 * on the console ownership for synchronization.
383 */
384 void (*write_atomic)(struct console *con, struct nbcon_write_context *wctxt);
385
386 /**
387 * @write_thread:
388 *
389 * NBCON callback to write out text in task context.
390 *
391 * This callback must be called only in task context with both
392 * device_lock() and the nbcon console acquired with
393 * NBCON_PRIO_NORMAL.
394 *
395 * The same rules for console ownership verification and unsafe
396 * sections handling applies as with write_atomic().
397 *
398 * The console ownership handling is necessary for synchronization
399 * against write_atomic() which is synchronized only via the context.
400 *
401 * The device_lock() provides the primary serialization for operations
402 * on the device. It might be as relaxed (mutex)[*] or as tight
403 * (disabled preemption and interrupts) as needed. It allows
404 * the kthread to operate in the least restrictive mode[**].
405 *
406 * [*] Standalone nbcon_context_try_acquire() is not safe with
407 * the preemption enabled, see nbcon_owner_matches(). But it
408 * can be safe when always called in the preemptive context
409 * under the device_lock().
410 *
411 * [**] The device_lock() makes sure that nbcon_context_try_acquire()
412 * would never need to spin which is important especially with
413 * PREEMPT_RT.
414 */
415 void (*write_thread)(struct console *con, struct nbcon_write_context *wctxt);
416
417 /**
418 * @device_lock:
419 *
420 * NBCON callback to begin synchronization with driver code.
421 *
422 * Console drivers typically must deal with access to the hardware
423 * via user input/output (such as an interactive login shell) and
424 * output of kernel messages via printk() calls. This callback is
425 * called by the printk-subsystem whenever it needs to synchronize
426 * with hardware access by the driver. It should be implemented to
427 * use whatever synchronization mechanism the driver is using for
428 * itself (for example, the port lock for uart serial consoles).
429 *
430 * The callback is always called from task context. It may use any
431 * synchronization method required by the driver.
432 *
433 * IMPORTANT: The callback MUST disable migration. The console driver
434 * may be using a synchronization mechanism that already takes
435 * care of this (such as spinlocks). Otherwise this function must
436 * explicitly call migrate_disable().
437 *
438 * The flags argument is provided as a convenience to the driver. It
439 * will be passed again to device_unlock(). It can be ignored if the
440 * driver does not need it.
441 */
442 void (*device_lock)(struct console *con, unsigned long *flags);
443
444 /**
445 * @device_unlock:
446 *
447 * NBCON callback to finish synchronization with driver code.
448 *
449 * It is the counterpart to device_lock().
450 *
451 * This callback is always called from task context. It must
452 * appropriately re-enable migration (depending on how device_lock()
453 * disabled migration).
454 *
455 * The flags argument is the value of the same variable that was
456 * passed to device_lock().
457 */
458 void (*device_unlock)(struct console *con, unsigned long flags);
459
460 atomic_t __private nbcon_state;
461 atomic_long_t __private nbcon_seq;
462 struct nbcon_context __private nbcon_device_ctxt;
463 atomic_long_t __private nbcon_prev_seq;
464
465 struct printk_buffers *pbufs;
466 struct task_struct *kthread;
467 struct rcuwait rcuwait;
468 struct irq_work irq_work;
469 };
470
471 #ifdef CONFIG_LOCKDEP
472 extern void lockdep_assert_console_list_lock_held(void);
473 #else
lockdep_assert_console_list_lock_held(void)474 static inline void lockdep_assert_console_list_lock_held(void)
475 {
476 }
477 #endif
478
479 #ifdef CONFIG_DEBUG_LOCK_ALLOC
480 extern bool console_srcu_read_lock_is_held(void);
481 #else
console_srcu_read_lock_is_held(void)482 static inline bool console_srcu_read_lock_is_held(void)
483 {
484 return 1;
485 }
486 #endif
487
488 extern int console_srcu_read_lock(void);
489 extern void console_srcu_read_unlock(int cookie);
490
491 extern void console_list_lock(void) __acquires(console_mutex);
492 extern void console_list_unlock(void) __releases(console_mutex);
493
494 extern struct hlist_head console_list;
495
496 /**
497 * console_srcu_read_flags - Locklessly read flags of a possibly registered
498 * console
499 * @con: struct console pointer of console to read flags from
500 *
501 * Locklessly reading @con->flags provides a consistent read value because
502 * there is at most one CPU modifying @con->flags and that CPU is using only
503 * read-modify-write operations to do so.
504 *
505 * Requires console_srcu_read_lock to be held, which implies that @con might
506 * be a registered console. The purpose of holding console_srcu_read_lock is
507 * to guarantee that the console state is valid (CON_SUSPENDED/CON_ENABLED)
508 * and that no exit/cleanup routines will run if the console is currently
509 * undergoing unregistration.
510 *
511 * If the caller is holding the console_list_lock or it is _certain_ that
512 * @con is not and will not become registered, the caller may read
513 * @con->flags directly instead.
514 *
515 * Context: Any context.
516 * Return: The current value of the @con->flags field.
517 */
console_srcu_read_flags(const struct console * con)518 static inline short console_srcu_read_flags(const struct console *con)
519 {
520 WARN_ON_ONCE(!console_srcu_read_lock_is_held());
521
522 /*
523 * The READ_ONCE() matches the WRITE_ONCE() when @flags are modified
524 * for registered consoles with console_srcu_write_flags().
525 */
526 return data_race(READ_ONCE(con->flags));
527 }
528
529 /**
530 * console_srcu_write_flags - Write flags for a registered console
531 * @con: struct console pointer of console to write flags to
532 * @flags: new flags value to write
533 *
534 * Only use this function to write flags for registered consoles. It
535 * requires holding the console_list_lock.
536 *
537 * Context: Any context.
538 */
console_srcu_write_flags(struct console * con,short flags)539 static inline void console_srcu_write_flags(struct console *con, short flags)
540 {
541 lockdep_assert_console_list_lock_held();
542
543 /* This matches the READ_ONCE() in console_srcu_read_flags(). */
544 WRITE_ONCE(con->flags, flags);
545 }
546
547 /* Variant of console_is_registered() when the console_list_lock is held. */
console_is_registered_locked(const struct console * con)548 static inline bool console_is_registered_locked(const struct console *con)
549 {
550 lockdep_assert_console_list_lock_held();
551 return !hlist_unhashed(&con->node);
552 }
553
554 /*
555 * console_is_registered - Check if the console is registered
556 * @con: struct console pointer of console to check
557 *
558 * Context: Process context. May sleep while acquiring console list lock.
559 * Return: true if the console is in the console list, otherwise false.
560 *
561 * If false is returned for a console that was previously registered, it
562 * can be assumed that the console's unregistration is fully completed,
563 * including the exit() callback after console list removal.
564 */
console_is_registered(const struct console * con)565 static inline bool console_is_registered(const struct console *con)
566 {
567 bool ret;
568
569 console_list_lock();
570 ret = console_is_registered_locked(con);
571 console_list_unlock();
572 return ret;
573 }
574
575 /**
576 * for_each_console_srcu() - Iterator over registered consoles
577 * @con: struct console pointer used as loop cursor
578 *
579 * Although SRCU guarantees the console list will be consistent, the
580 * struct console fields may be updated by other CPUs while iterating.
581 *
582 * Requires console_srcu_read_lock to be held. Can be invoked from
583 * any context.
584 */
585 #define for_each_console_srcu(con) \
586 hlist_for_each_entry_srcu(con, &console_list, node, \
587 console_srcu_read_lock_is_held())
588
589 /**
590 * for_each_console() - Iterator over registered consoles
591 * @con: struct console pointer used as loop cursor
592 *
593 * The console list and the &console.flags are immutable while iterating.
594 *
595 * Requires console_list_lock to be held.
596 */
597 #define for_each_console(con) \
598 lockdep_assert_console_list_lock_held(); \
599 hlist_for_each_entry(con, &console_list, node)
600
601 #ifdef CONFIG_PRINTK
602 extern void nbcon_cpu_emergency_enter(void);
603 extern void nbcon_cpu_emergency_exit(void);
604 extern bool nbcon_can_proceed(struct nbcon_write_context *wctxt);
605 extern bool nbcon_enter_unsafe(struct nbcon_write_context *wctxt);
606 extern bool nbcon_exit_unsafe(struct nbcon_write_context *wctxt);
607 extern void nbcon_reacquire_nobuf(struct nbcon_write_context *wctxt);
608 #else
nbcon_cpu_emergency_enter(void)609 static inline void nbcon_cpu_emergency_enter(void) { }
nbcon_cpu_emergency_exit(void)610 static inline void nbcon_cpu_emergency_exit(void) { }
nbcon_can_proceed(struct nbcon_write_context * wctxt)611 static inline bool nbcon_can_proceed(struct nbcon_write_context *wctxt) { return false; }
nbcon_enter_unsafe(struct nbcon_write_context * wctxt)612 static inline bool nbcon_enter_unsafe(struct nbcon_write_context *wctxt) { return false; }
nbcon_exit_unsafe(struct nbcon_write_context * wctxt)613 static inline bool nbcon_exit_unsafe(struct nbcon_write_context *wctxt) { return false; }
nbcon_reacquire_nobuf(struct nbcon_write_context * wctxt)614 static inline void nbcon_reacquire_nobuf(struct nbcon_write_context *wctxt) { }
615 #endif
616
617 extern int console_set_on_cmdline;
618 extern struct console *early_console;
619
620 enum con_flush_mode {
621 CONSOLE_FLUSH_PENDING,
622 CONSOLE_REPLAY_ALL,
623 };
624
625 extern int add_preferred_console(const char *name, const short idx, char *options);
626 extern void console_force_preferred_locked(struct console *con);
627 extern void register_console(struct console *);
628 extern int unregister_console(struct console *);
629 extern void console_lock(void);
630 extern int console_trylock(void);
631 extern void console_unlock(void);
632 extern void console_conditional_schedule(void);
633 extern void console_unblank(void);
634 extern void console_flush_on_panic(enum con_flush_mode mode);
635 extern struct tty_driver *console_device(int *);
636 extern void console_stop(struct console *);
637 extern void console_start(struct console *);
638 extern int is_console_locked(void);
639 extern int braille_register_console(struct console *, int index,
640 char *console_options, char *braille_options);
641 extern int braille_unregister_console(struct console *);
642 #ifdef CONFIG_TTY
643 extern void console_sysfs_notify(void);
644 #else
console_sysfs_notify(void)645 static inline void console_sysfs_notify(void)
646 { }
647 #endif
648 extern bool console_suspend_enabled;
649
650 /* Suspend and resume console messages over PM events */
651 extern void suspend_console(void);
652 extern void resume_console(void);
653
654 int mda_console_init(void);
655
656 void vcs_make_sysfs(int index);
657 void vcs_remove_sysfs(int index);
658
659 /* Some debug stub to catch some of the obvious races in the VT code */
660 #define WARN_CONSOLE_UNLOCKED() \
661 WARN_ON(!atomic_read(&ignore_console_lock_warning) && \
662 !is_console_locked() && !oops_in_progress)
663 /*
664 * Increment ignore_console_lock_warning if you need to quiet
665 * WARN_CONSOLE_UNLOCKED() for debugging purposes.
666 */
667 extern atomic_t ignore_console_lock_warning;
668
669 extern void console_init(void);
670
671 /* For deferred console takeover */
672 void dummycon_register_output_notifier(struct notifier_block *nb);
673 void dummycon_unregister_output_notifier(struct notifier_block *nb);
674
675 #endif /* _LINUX_CONSOLE_H */
676