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 * @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 */
86 struct 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
127 extern const struct consw *conswitchp;
128
129 extern const struct consw dummy_con; /* dummy console buffer */
130 extern const struct consw vga_con; /* VGA text console */
131 extern const struct consw newport_con; /* SGI Newport console */
132
133 struct screen_info;
134 #ifdef CONFIG_VGA_CONSOLE
135 void vgacon_register_screen(struct screen_info *si);
136 #else
137 static inline void vgacon_register_screen(struct screen_info *si) { }
138 #endif
139
140 int con_is_bound(const struct consw *csw);
141 int do_unregister_con_driver(const struct consw *csw);
142 int do_take_over_console(const struct consw *sw, int first, int last, int deflt);
143 void give_up_console(const struct consw *sw);
144 #ifdef CONFIG_VT
145 void con_debug_enter(struct vc_data *vc);
146 void con_debug_leave(void);
147 #else
148 static inline void con_debug_enter(struct vc_data *vc) { }
149 static 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 */
187 enum 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 */
217 struct 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 */
236 static_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 */
250 enum 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
258 struct console;
259 struct 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 */
274 struct 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 */
296 struct 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 */
328 struct 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
356 extern void lockdep_assert_console_list_lock_held(void);
357 #else
358 static inline void lockdep_assert_console_list_lock_held(void)
359 {
360 }
361 #endif
362
363 #ifdef CONFIG_DEBUG_LOCK_ALLOC
364 extern bool console_srcu_read_lock_is_held(void);
365 #else
366 static inline bool console_srcu_read_lock_is_held(void)
367 {
368 return 1;
369 }
370 #endif
371
372 extern int console_srcu_read_lock(void);
373 extern void console_srcu_read_unlock(int cookie);
374
375 extern void console_list_lock(void) __acquires(console_mutex);
376 extern void console_list_unlock(void) __releases(console_mutex);
377
378 extern 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 */
394 static 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 */
417 static 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. */
426 static 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 */
443 static 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
480 extern bool nbcon_can_proceed(struct nbcon_write_context *wctxt);
481 extern bool nbcon_enter_unsafe(struct nbcon_write_context *wctxt);
482 extern bool nbcon_exit_unsafe(struct nbcon_write_context *wctxt);
483 #else
484 static inline bool nbcon_can_proceed(struct nbcon_write_context *wctxt) { return false; }
485 static inline bool nbcon_enter_unsafe(struct nbcon_write_context *wctxt) { return false; }
486 static inline bool nbcon_exit_unsafe(struct nbcon_write_context *wctxt) { return false; }
487 #endif
488
489 extern int console_set_on_cmdline;
490 extern struct console *early_console;
491
492 enum con_flush_mode {
493 CONSOLE_FLUSH_PENDING,
494 CONSOLE_REPLAY_ALL,
495 };
496
497 extern int add_preferred_console(const char *name, const short idx, char *options);
498 extern void console_force_preferred_locked(struct console *con);
499 extern void register_console(struct console *);
500 extern int unregister_console(struct console *);
501 extern void console_lock(void);
502 extern int console_trylock(void);
503 extern void console_unlock(void);
504 extern void console_conditional_schedule(void);
505 extern void console_unblank(void);
506 extern void console_flush_on_panic(enum con_flush_mode mode);
507 extern struct tty_driver *console_device(int *);
508 extern void console_stop(struct console *);
509 extern void console_start(struct console *);
510 extern int is_console_locked(void);
511 extern int braille_register_console(struct console *, int index,
512 char *console_options, char *braille_options);
513 extern int braille_unregister_console(struct console *);
514 #ifdef CONFIG_TTY
515 extern void console_sysfs_notify(void);
516 #else
517 static inline void console_sysfs_notify(void)
518 { }
519 #endif
520 extern bool console_suspend_enabled;
521
522 /* Suspend and resume console messages over PM events */
523 extern void suspend_console(void);
524 extern void resume_console(void);
525
526 int mda_console_init(void);
527
528 void vcs_make_sysfs(int index);
529 void 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 */
539 extern atomic_t ignore_console_lock_warning;
540
541 extern void console_init(void);
542
543 /* For deferred console takeover */
544 void dummycon_register_output_notifier(struct notifier_block *nb);
545 void dummycon_unregister_output_notifier(struct notifier_block *nb);
546
547 #endif /* _LINUX_CONSOLE_H */
548
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