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  */
158 enum cons_flags {
159 	CON_PRINTBUFFER		= BIT(0),
160 	CON_CONSDEV		= BIT(1),
161 	CON_ENABLED		= BIT(2),
162 	CON_BOOT		= BIT(3),
163 	CON_ANYTIME		= BIT(4),
164 	CON_BRL			= BIT(5),
165 	CON_EXTENDED		= BIT(6),
166 };
167 
168 /**
169  * struct console - The console descriptor structure
170  * @name:		The name of the console driver
171  * @write:		Write callback to output messages (Optional)
172  * @read:		Read callback for console input (Optional)
173  * @device:		The underlying TTY device driver (Optional)
174  * @unblank:		Callback to unblank the console (Optional)
175  * @setup:		Callback for initializing the console (Optional)
176  * @exit:		Callback for teardown of the console (Optional)
177  * @match:		Callback for matching a console (Optional)
178  * @flags:		Console flags. See enum cons_flags
179  * @index:		Console index, e.g. port number
180  * @cflag:		TTY control mode flags
181  * @ispeed:		TTY input speed
182  * @ospeed:		TTY output speed
183  * @seq:		Sequence number of the next ringbuffer record to print
184  * @dropped:		Number of unreported dropped ringbuffer records
185  * @data:		Driver private data
186  * @node:		hlist node for the console list
187  */
188 struct console {
189 	char			name[16];
190 	void			(*write)(struct console *co, const char *s, unsigned int count);
191 	int			(*read)(struct console *co, char *s, unsigned int count);
192 	struct tty_driver	*(*device)(struct console *co, int *index);
193 	void			(*unblank)(void);
194 	int			(*setup)(struct console *co, char *options);
195 	int			(*exit)(struct console *co);
196 	int			(*match)(struct console *co, char *name, int idx, char *options);
197 	short			flags;
198 	short			index;
199 	int			cflag;
200 	uint			ispeed;
201 	uint			ospeed;
202 	u64			seq;
203 	unsigned long		dropped;
204 	void			*data;
205 	struct hlist_node	node;
206 };
207 
208 #ifdef CONFIG_LOCKDEP
209 extern void lockdep_assert_console_list_lock_held(void);
210 #else
lockdep_assert_console_list_lock_held(void)211 static inline void lockdep_assert_console_list_lock_held(void)
212 {
213 }
214 #endif
215 
216 #ifdef CONFIG_DEBUG_LOCK_ALLOC
217 extern bool console_srcu_read_lock_is_held(void);
218 #else
console_srcu_read_lock_is_held(void)219 static inline bool console_srcu_read_lock_is_held(void)
220 {
221 	return 1;
222 }
223 #endif
224 
225 extern int console_srcu_read_lock(void);
226 extern void console_srcu_read_unlock(int cookie);
227 
228 extern void console_list_lock(void) __acquires(console_mutex);
229 extern void console_list_unlock(void) __releases(console_mutex);
230 
231 extern struct hlist_head console_list;
232 
233 /**
234  * console_srcu_read_flags - Locklessly read the console flags
235  * @con:	struct console pointer of console to read flags from
236  *
237  * This function provides the necessary READ_ONCE() and data_race()
238  * notation for locklessly reading the console flags. The READ_ONCE()
239  * in this function matches the WRITE_ONCE() when @flags are modified
240  * for registered consoles with console_srcu_write_flags().
241  *
242  * Only use this function to read console flags when locklessly
243  * iterating the console list via srcu.
244  *
245  * Context: Any context.
246  */
console_srcu_read_flags(const struct console * con)247 static inline short console_srcu_read_flags(const struct console *con)
248 {
249 	WARN_ON_ONCE(!console_srcu_read_lock_is_held());
250 
251 	/*
252 	 * Locklessly reading console->flags provides a consistent
253 	 * read value because there is at most one CPU modifying
254 	 * console->flags and that CPU is using only read-modify-write
255 	 * operations to do so.
256 	 */
257 	return data_race(READ_ONCE(con->flags));
258 }
259 
260 /**
261  * console_srcu_write_flags - Write flags for a registered console
262  * @con:	struct console pointer of console to write flags to
263  * @flags:	new flags value to write
264  *
265  * Only use this function to write flags for registered consoles. It
266  * requires holding the console_list_lock.
267  *
268  * Context: Any context.
269  */
console_srcu_write_flags(struct console * con,short flags)270 static inline void console_srcu_write_flags(struct console *con, short flags)
271 {
272 	lockdep_assert_console_list_lock_held();
273 
274 	/* This matches the READ_ONCE() in console_srcu_read_flags(). */
275 	WRITE_ONCE(con->flags, flags);
276 }
277 
278 /* Variant of console_is_registered() when the console_list_lock is held. */
console_is_registered_locked(const struct console * con)279 static inline bool console_is_registered_locked(const struct console *con)
280 {
281 	lockdep_assert_console_list_lock_held();
282 	return !hlist_unhashed(&con->node);
283 }
284 
285 /*
286  * console_is_registered - Check if the console is registered
287  * @con:	struct console pointer of console to check
288  *
289  * Context: Process context. May sleep while acquiring console list lock.
290  * Return: true if the console is in the console list, otherwise false.
291  *
292  * If false is returned for a console that was previously registered, it
293  * can be assumed that the console's unregistration is fully completed,
294  * including the exit() callback after console list removal.
295  */
console_is_registered(const struct console * con)296 static inline bool console_is_registered(const struct console *con)
297 {
298 	bool ret;
299 
300 	console_list_lock();
301 	ret = console_is_registered_locked(con);
302 	console_list_unlock();
303 	return ret;
304 }
305 
306 /**
307  * for_each_console_srcu() - Iterator over registered consoles
308  * @con:	struct console pointer used as loop cursor
309  *
310  * Although SRCU guarantees the console list will be consistent, the
311  * struct console fields may be updated by other CPUs while iterating.
312  *
313  * Requires console_srcu_read_lock to be held. Can be invoked from
314  * any context.
315  */
316 #define for_each_console_srcu(con)					\
317 	hlist_for_each_entry_srcu(con, &console_list, node,		\
318 				  console_srcu_read_lock_is_held())
319 
320 /**
321  * for_each_console() - Iterator over registered consoles
322  * @con:	struct console pointer used as loop cursor
323  *
324  * The console list and the console->flags are immutable while iterating.
325  *
326  * Requires console_list_lock to be held.
327  */
328 #define for_each_console(con)						\
329 	lockdep_assert_console_list_lock_held();			\
330 	hlist_for_each_entry(con, &console_list, node)
331 
332 extern int console_set_on_cmdline;
333 extern struct console *early_console;
334 
335 enum con_flush_mode {
336 	CONSOLE_FLUSH_PENDING,
337 	CONSOLE_REPLAY_ALL,
338 };
339 
340 extern int add_preferred_console(char *name, int idx, char *options);
341 extern void console_force_preferred_locked(struct console *con);
342 extern void register_console(struct console *);
343 extern int unregister_console(struct console *);
344 extern void console_lock(void);
345 extern int console_trylock(void);
346 extern void console_unlock(void);
347 extern void console_conditional_schedule(void);
348 extern void console_unblank(void);
349 extern void console_flush_on_panic(enum con_flush_mode mode);
350 extern struct tty_driver *console_device(int *);
351 extern void console_stop(struct console *);
352 extern void console_start(struct console *);
353 extern int is_console_locked(void);
354 extern int braille_register_console(struct console *, int index,
355 		char *console_options, char *braille_options);
356 extern int braille_unregister_console(struct console *);
357 #ifdef CONFIG_TTY
358 extern void console_sysfs_notify(void);
359 #else
console_sysfs_notify(void)360 static inline void console_sysfs_notify(void)
361 { }
362 #endif
363 extern bool console_suspend_enabled;
364 
365 /* Suspend and resume console messages over PM events */
366 extern void suspend_console(void);
367 extern void resume_console(void);
368 
369 int mda_console_init(void);
370 
371 void vcs_make_sysfs(int index);
372 void vcs_remove_sysfs(int index);
373 
374 /* Some debug stub to catch some of the obvious races in the VT code */
375 #define WARN_CONSOLE_UNLOCKED()						\
376 	WARN_ON(!atomic_read(&ignore_console_lock_warning) &&		\
377 		!is_console_locked() && !oops_in_progress)
378 /*
379  * Increment ignore_console_lock_warning if you need to quiet
380  * WARN_CONSOLE_UNLOCKED() for debugging purposes.
381  */
382 extern atomic_t ignore_console_lock_warning;
383 
384 /* VESA Blanking Levels */
385 #define VESA_NO_BLANKING        0
386 #define VESA_VSYNC_SUSPEND      1
387 #define VESA_HSYNC_SUSPEND      2
388 #define VESA_POWERDOWN          3
389 
390 extern void console_init(void);
391 
392 /* For deferred console takeover */
393 void dummycon_register_output_notifier(struct notifier_block *nb);
394 void dummycon_unregister_output_notifier(struct notifier_block *nb);
395 
396 #endif /* _LINUX_CONSOLE_H */
397