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 int con_is_bound(const struct consw *csw);
105 int do_unregister_con_driver(const struct consw *csw);
106 int do_take_over_console(const struct consw *sw, int first, int last, int deflt);
107 void give_up_console(const struct consw *sw);
108 #ifdef CONFIG_HW_CONSOLE
109 int con_debug_enter(struct vc_data *vc);
110 int con_debug_leave(void);
111 #else
con_debug_enter(struct vc_data * vc)112 static inline int con_debug_enter(struct vc_data *vc)
113 {
114 	return 0;
115 }
con_debug_leave(void)116 static inline int con_debug_leave(void)
117 {
118 	return 0;
119 }
120 #endif
121 
122 /* cursor */
123 #define CM_DRAW     (1)
124 #define CM_ERASE    (2)
125 #define CM_MOVE     (3)
126 
127 /*
128  * The interface for a console, or any other device that wants to capture
129  * console messages (printer driver?)
130  */
131 
132 /**
133  * cons_flags - General console flags
134  * @CON_PRINTBUFFER:	Used by newly registered consoles to avoid duplicate
135  *			output of messages that were already shown by boot
136  *			consoles or read by userspace via syslog() syscall.
137  * @CON_CONSDEV:	Indicates that the console driver is backing
138  *			/dev/console.
139  * @CON_ENABLED:	Indicates if a console is allowed to print records. If
140  *			false, the console also will not advance to later
141  *			records.
142  * @CON_BOOT:		Marks the console driver as early console driver which
143  *			is used during boot before the real driver becomes
144  *			available. It will be automatically unregistered
145  *			when the real console driver is registered unless
146  *			"keep_bootcon" parameter is used.
147  * @CON_ANYTIME:	A misnomed historical flag which tells the core code
148  *			that the legacy @console::write callback can be invoked
149  *			on a CPU which is marked OFFLINE. That is misleading as
150  *			it suggests that there is no contextual limit for
151  *			invoking the callback. The original motivation was
152  *			readiness of the per-CPU areas.
153  * @CON_BRL:		Indicates a braille device which is exempt from
154  *			receiving the printk spam for obvious reasons.
155  * @CON_EXTENDED:	The console supports the extended output format of
156  *			/dev/kmesg which requires a larger output buffer.
157  * @CON_SUSPENDED:	Indicates if a console is suspended. If true, the
158  *			printing callbacks must not be called.
159  */
160 enum cons_flags {
161 	CON_PRINTBUFFER		= BIT(0),
162 	CON_CONSDEV		= BIT(1),
163 	CON_ENABLED		= BIT(2),
164 	CON_BOOT		= BIT(3),
165 	CON_ANYTIME		= BIT(4),
166 	CON_BRL			= BIT(5),
167 	CON_EXTENDED		= BIT(6),
168 	CON_SUSPENDED		= BIT(7),
169 };
170 
171 /**
172  * struct console - The console descriptor structure
173  * @name:		The name of the console driver
174  * @write:		Write callback to output messages (Optional)
175  * @read:		Read callback for console input (Optional)
176  * @device:		The underlying TTY device driver (Optional)
177  * @unblank:		Callback to unblank the console (Optional)
178  * @setup:		Callback for initializing the console (Optional)
179  * @exit:		Callback for teardown of the console (Optional)
180  * @match:		Callback for matching a console (Optional)
181  * @flags:		Console flags. See enum cons_flags
182  * @index:		Console index, e.g. port number
183  * @cflag:		TTY control mode flags
184  * @ispeed:		TTY input speed
185  * @ospeed:		TTY output speed
186  * @seq:		Sequence number of the next ringbuffer record to print
187  * @dropped:		Number of unreported dropped ringbuffer records
188  * @data:		Driver private data
189  * @node:		hlist node for the console list
190  */
191 struct console {
192 	char			name[16];
193 	void			(*write)(struct console *co, const char *s, unsigned int count);
194 	int			(*read)(struct console *co, char *s, unsigned int count);
195 	struct tty_driver	*(*device)(struct console *co, int *index);
196 	void			(*unblank)(void);
197 	int			(*setup)(struct console *co, char *options);
198 	int			(*exit)(struct console *co);
199 	int			(*match)(struct console *co, char *name, int idx, char *options);
200 	short			flags;
201 	short			index;
202 	int			cflag;
203 	uint			ispeed;
204 	uint			ospeed;
205 	u64			seq;
206 	unsigned long		dropped;
207 	void			*data;
208 	struct hlist_node	node;
209 };
210 
211 #ifdef CONFIG_LOCKDEP
212 extern void lockdep_assert_console_list_lock_held(void);
213 #else
lockdep_assert_console_list_lock_held(void)214 static inline void lockdep_assert_console_list_lock_held(void)
215 {
216 }
217 #endif
218 
219 #ifdef CONFIG_DEBUG_LOCK_ALLOC
220 extern bool console_srcu_read_lock_is_held(void);
221 #else
console_srcu_read_lock_is_held(void)222 static inline bool console_srcu_read_lock_is_held(void)
223 {
224 	return 1;
225 }
226 #endif
227 
228 extern int console_srcu_read_lock(void);
229 extern void console_srcu_read_unlock(int cookie);
230 
231 extern void console_list_lock(void) __acquires(console_mutex);
232 extern void console_list_unlock(void) __releases(console_mutex);
233 
234 extern struct hlist_head console_list;
235 
236 /**
237  * console_srcu_read_flags - Locklessly read the console flags
238  * @con:	struct console pointer of console to read flags from
239  *
240  * This function provides the necessary READ_ONCE() and data_race()
241  * notation for locklessly reading the console flags. The READ_ONCE()
242  * in this function matches the WRITE_ONCE() when @flags are modified
243  * for registered consoles with console_srcu_write_flags().
244  *
245  * Only use this function to read console flags when locklessly
246  * iterating the console list via srcu.
247  *
248  * Context: Any context.
249  */
console_srcu_read_flags(const struct console * con)250 static inline short console_srcu_read_flags(const struct console *con)
251 {
252 	WARN_ON_ONCE(!console_srcu_read_lock_is_held());
253 
254 	/*
255 	 * Locklessly reading console->flags provides a consistent
256 	 * read value because there is at most one CPU modifying
257 	 * console->flags and that CPU is using only read-modify-write
258 	 * operations to do so.
259 	 */
260 	return data_race(READ_ONCE(con->flags));
261 }
262 
263 /**
264  * console_srcu_write_flags - Write flags for a registered console
265  * @con:	struct console pointer of console to write flags to
266  * @flags:	new flags value to write
267  *
268  * Only use this function to write flags for registered consoles. It
269  * requires holding the console_list_lock.
270  *
271  * Context: Any context.
272  */
console_srcu_write_flags(struct console * con,short flags)273 static inline void console_srcu_write_flags(struct console *con, short flags)
274 {
275 	lockdep_assert_console_list_lock_held();
276 
277 	/* This matches the READ_ONCE() in console_srcu_read_flags(). */
278 	WRITE_ONCE(con->flags, flags);
279 }
280 
281 /* Variant of console_is_registered() when the console_list_lock is held. */
console_is_registered_locked(const struct console * con)282 static inline bool console_is_registered_locked(const struct console *con)
283 {
284 	lockdep_assert_console_list_lock_held();
285 	return !hlist_unhashed(&con->node);
286 }
287 
288 /*
289  * console_is_registered - Check if the console is registered
290  * @con:	struct console pointer of console to check
291  *
292  * Context: Process context. May sleep while acquiring console list lock.
293  * Return: true if the console is in the console list, otherwise false.
294  *
295  * If false is returned for a console that was previously registered, it
296  * can be assumed that the console's unregistration is fully completed,
297  * including the exit() callback after console list removal.
298  */
console_is_registered(const struct console * con)299 static inline bool console_is_registered(const struct console *con)
300 {
301 	bool ret;
302 
303 	console_list_lock();
304 	ret = console_is_registered_locked(con);
305 	console_list_unlock();
306 	return ret;
307 }
308 
309 /**
310  * for_each_console_srcu() - Iterator over registered consoles
311  * @con:	struct console pointer used as loop cursor
312  *
313  * Although SRCU guarantees the console list will be consistent, the
314  * struct console fields may be updated by other CPUs while iterating.
315  *
316  * Requires console_srcu_read_lock to be held. Can be invoked from
317  * any context.
318  */
319 #define for_each_console_srcu(con)					\
320 	hlist_for_each_entry_srcu(con, &console_list, node,		\
321 				  console_srcu_read_lock_is_held())
322 
323 /**
324  * for_each_console() - Iterator over registered consoles
325  * @con:	struct console pointer used as loop cursor
326  *
327  * The console list and the console->flags are immutable while iterating.
328  *
329  * Requires console_list_lock to be held.
330  */
331 #define for_each_console(con)						\
332 	lockdep_assert_console_list_lock_held();			\
333 	hlist_for_each_entry(con, &console_list, node)
334 
335 extern int console_set_on_cmdline;
336 extern struct console *early_console;
337 
338 enum con_flush_mode {
339 	CONSOLE_FLUSH_PENDING,
340 	CONSOLE_REPLAY_ALL,
341 };
342 
343 extern int add_preferred_console(char *name, int idx, char *options);
344 extern void console_force_preferred_locked(struct console *con);
345 extern void register_console(struct console *);
346 extern int unregister_console(struct console *);
347 extern void console_lock(void);
348 extern int console_trylock(void);
349 extern void console_unlock(void);
350 extern void console_conditional_schedule(void);
351 extern void console_unblank(void);
352 extern void console_flush_on_panic(enum con_flush_mode mode);
353 extern struct tty_driver *console_device(int *);
354 extern void console_stop(struct console *);
355 extern void console_start(struct console *);
356 extern int is_console_locked(void);
357 extern int braille_register_console(struct console *, int index,
358 		char *console_options, char *braille_options);
359 extern int braille_unregister_console(struct console *);
360 #ifdef CONFIG_TTY
361 extern void console_sysfs_notify(void);
362 #else
console_sysfs_notify(void)363 static inline void console_sysfs_notify(void)
364 { }
365 #endif
366 extern bool console_suspend_enabled;
367 
368 /* Suspend and resume console messages over PM events */
369 extern void suspend_console(void);
370 extern void resume_console(void);
371 
372 int mda_console_init(void);
373 
374 void vcs_make_sysfs(int index);
375 void vcs_remove_sysfs(int index);
376 
377 /* Some debug stub to catch some of the obvious races in the VT code */
378 #define WARN_CONSOLE_UNLOCKED()						\
379 	WARN_ON(!atomic_read(&ignore_console_lock_warning) &&		\
380 		!is_console_locked() && !oops_in_progress)
381 /*
382  * Increment ignore_console_lock_warning if you need to quiet
383  * WARN_CONSOLE_UNLOCKED() for debugging purposes.
384  */
385 extern atomic_t ignore_console_lock_warning;
386 
387 /* VESA Blanking Levels */
388 #define VESA_NO_BLANKING        0
389 #define VESA_VSYNC_SUSPEND      1
390 #define VESA_HSYNC_SUSPEND      2
391 #define VESA_POWERDOWN          3
392 
393 extern void console_init(void);
394 
395 /* For deferred console takeover */
396 void dummycon_register_output_notifier(struct notifier_block *nb);
397 void dummycon_unregister_output_notifier(struct notifier_block *nb);
398 
399 #endif /* _LINUX_CONSOLE_H */
400