2  *  linux/include/linux/console.h
11  * 10-Mar-94: Arno Griffioen: Conversion for vt100 emulator port from PC LINUX
37  * struct consw - callbacks for consoles
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.
83 	 * Flush the video console driver's scrollback buffer
87 	 * Prepare the console for the debugger.  This includes, but is not
88 	 * limited to, unblanking the console, loading an appropriate
93 	 * Restore the console to its pre-debug state as closely as possible.
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  */
128  * The interface for a console, or any other device that wants to capture
129  * console messages (printer driver?)
133  * cons_flags - General console flags
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
142  * @CON_BOOT:		Marks the console driver as early console driver which
145  *			when the real console driver is registered unless
148  *			that the legacy @console::write callback can be invoked
152  *			readiness of the per-CPU areas.
155  * @CON_EXTENDED:	The console supports the extended output format of
157  * @CON_SUSPENDED:	Indicates if a console is suspended. If true, the
172  * struct console - The console descriptor structure
173  * @name:		The name of the console driver
175  * @read:		Read callback for console input (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
189  * @node:		hlist node for the console list
191 struct console {  struct
193 	void			(*write)(struct console *co, const char *s, unsigned int count);  argument
194 	int			(*read)(struct console *co, char *s, unsigned int count);  argument
195 	struct tty_driver	*(*device)(struct console *co, int *index);  argument
197 	int			(*setup)(struct console *co, char *options);  argument
198 	int			(*exit)(struct console *co);  argument
199 	int			(*match)(struct console *co, char *name, int idx, char *options);  argument
237  * console_srcu_read_flags - Locklessly read the console flags
238  * @con:	struct console pointer of console to read flags from
241  * notation for locklessly reading the console flags. The READ_ONCE()
245  * Only use this function to read console flags when locklessly
246  * iterating the console list via srcu.
250 static inline short console_srcu_read_flags(const struct console *con)  in console_srcu_read_flags()
255 	 * Locklessly reading console->flags provides a consistent  in console_srcu_read_flags()
257 	 * console->flags and that CPU is using only read-modify-write  in console_srcu_read_flags()
260 	return data_race(READ_ONCE(con->flags));  in console_srcu_read_flags()
264  * console_srcu_write_flags - Write flags for a registered console
265  * @con:	struct console pointer of console to write flags to
273 static inline void console_srcu_write_flags(struct console *con, short flags)  in console_srcu_write_flags()
278 	WRITE_ONCE(con->flags, flags);  in console_srcu_write_flags()
282 static inline bool console_is_registered_locked(const struct console *con)  in console_is_registered_locked()
285 	return !hlist_unhashed(&con->node);  in console_is_registered_locked()
289  * console_is_registered - Check if the console is registered
290  * @con:	struct console pointer of console to check
292  * Context: Process context. May sleep while acquiring console list lock.
293  * Return: true if the console is in the console list, otherwise false.
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.
299 static inline bool console_is_registered(const struct console *con)  in console_is_registered()
310  * for_each_console_srcu() - Iterator over registered consoles
311  * @con:	struct console pointer used as loop cursor
313  * Although SRCU guarantees the console list will be consistent, the
314  * struct console fields may be updated by other CPUs while iterating.
324  * for_each_console() - Iterator over registered consoles
325  * @con:	struct console pointer used as loop cursor
327  * The console list and the console->flags are immutable while iterating.
336 extern struct console *early_console;
344 extern void console_force_preferred_locked(struct console *con);
345 extern void register_console(struct console *);
346 extern int unregister_console(struct console *);
354 extern void console_stop(struct console *);
355 extern void console_start(struct console *);
357 extern int braille_register_console(struct console *, int index,
359 extern int braille_unregister_console(struct console *);
368 /* Suspend and resume console messages over PM events */
395 /* For deferred console takeover */