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