xref: /linux-6.15/include/linux/serial_core.h (revision f9008285)
1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 /*
3  *  linux/drivers/char/serial_core.h
4  *
5  *  Copyright (C) 2000 Deep Blue Solutions Ltd.
6  */
7 #ifndef LINUX_SERIAL_CORE_H
8 #define LINUX_SERIAL_CORE_H
9 
10 #include <linux/bitops.h>
11 #include <linux/compiler.h>
12 #include <linux/console.h>
13 #include <linux/interrupt.h>
14 #include <linux/circ_buf.h>
15 #include <linux/spinlock.h>
16 #include <linux/sched.h>
17 #include <linux/tty.h>
18 #include <linux/mutex.h>
19 #include <linux/sysrq.h>
20 #include <uapi/linux/serial_core.h>
21 
22 #ifdef CONFIG_SERIAL_CORE_CONSOLE
23 #define uart_console(port) \
24 	((port)->cons && (port)->cons->index == (port)->line)
25 #else
26 #define uart_console(port)      ({ (void)port; 0; })
27 #endif
28 
29 struct uart_port;
30 struct serial_struct;
31 struct device;
32 struct gpio_desc;
33 
34 /*
35  * This structure describes all the operations that can be done on the
36  * physical hardware.  See Documentation/driver-api/serial/driver.rst for details.
37  */
38 struct uart_ops {
39 	unsigned int	(*tx_empty)(struct uart_port *);
40 	void		(*set_mctrl)(struct uart_port *, unsigned int mctrl);
41 	unsigned int	(*get_mctrl)(struct uart_port *);
42 	void		(*stop_tx)(struct uart_port *);
43 	void		(*start_tx)(struct uart_port *);
44 	void		(*throttle)(struct uart_port *);
45 	void		(*unthrottle)(struct uart_port *);
46 	void		(*send_xchar)(struct uart_port *, char ch);
47 	void		(*stop_rx)(struct uart_port *);
48 	void		(*start_rx)(struct uart_port *);
49 	void		(*enable_ms)(struct uart_port *);
50 	void		(*break_ctl)(struct uart_port *, int ctl);
51 	int		(*startup)(struct uart_port *);
52 	void		(*shutdown)(struct uart_port *);
53 	void		(*flush_buffer)(struct uart_port *);
54 	void		(*set_termios)(struct uart_port *, struct ktermios *new,
55 				       struct ktermios *old);
56 	void		(*set_ldisc)(struct uart_port *, struct ktermios *);
57 	void		(*pm)(struct uart_port *, unsigned int state,
58 			      unsigned int oldstate);
59 
60 	/*
61 	 * Return a string describing the type of the port
62 	 */
63 	const char	*(*type)(struct uart_port *);
64 
65 	/*
66 	 * Release IO and memory resources used by the port.
67 	 * This includes iounmap if necessary.
68 	 */
69 	void		(*release_port)(struct uart_port *);
70 
71 	/*
72 	 * Request IO and memory resources used by the port.
73 	 * This includes iomapping the port if necessary.
74 	 */
75 	int		(*request_port)(struct uart_port *);
76 	void		(*config_port)(struct uart_port *, int);
77 	int		(*verify_port)(struct uart_port *, struct serial_struct *);
78 	int		(*ioctl)(struct uart_port *, unsigned int, unsigned long);
79 #ifdef CONFIG_CONSOLE_POLL
80 	int		(*poll_init)(struct uart_port *);
81 	void		(*poll_put_char)(struct uart_port *, unsigned char);
82 	int		(*poll_get_char)(struct uart_port *);
83 #endif
84 };
85 
86 #define NO_POLL_CHAR		0x00ff0000
87 #define UART_CONFIG_TYPE	(1 << 0)
88 #define UART_CONFIG_IRQ		(1 << 1)
89 
90 struct uart_icount {
91 	__u32	cts;
92 	__u32	dsr;
93 	__u32	rng;
94 	__u32	dcd;
95 	__u32	rx;
96 	__u32	tx;
97 	__u32	frame;
98 	__u32	overrun;
99 	__u32	parity;
100 	__u32	brk;
101 	__u32	buf_overrun;
102 };
103 
104 typedef unsigned int __bitwise upf_t;
105 typedef unsigned int __bitwise upstat_t;
106 
107 struct uart_port {
108 	spinlock_t		lock;			/* port lock */
109 	unsigned long		iobase;			/* in/out[bwl] */
110 	unsigned char __iomem	*membase;		/* read/write[bwl] */
111 	unsigned int		(*serial_in)(struct uart_port *, int);
112 	void			(*serial_out)(struct uart_port *, int, int);
113 	void			(*set_termios)(struct uart_port *,
114 				               struct ktermios *new,
115 				               struct ktermios *old);
116 	void			(*set_ldisc)(struct uart_port *,
117 					     struct ktermios *);
118 	unsigned int		(*get_mctrl)(struct uart_port *);
119 	void			(*set_mctrl)(struct uart_port *, unsigned int);
120 	unsigned int		(*get_divisor)(struct uart_port *,
121 					       unsigned int baud,
122 					       unsigned int *frac);
123 	void			(*set_divisor)(struct uart_port *,
124 					       unsigned int baud,
125 					       unsigned int quot,
126 					       unsigned int quot_frac);
127 	int			(*startup)(struct uart_port *port);
128 	void			(*shutdown)(struct uart_port *port);
129 	void			(*throttle)(struct uart_port *port);
130 	void			(*unthrottle)(struct uart_port *port);
131 	int			(*handle_irq)(struct uart_port *);
132 	void			(*pm)(struct uart_port *, unsigned int state,
133 				      unsigned int old);
134 	void			(*handle_break)(struct uart_port *);
135 	int			(*rs485_config)(struct uart_port *,
136 						struct serial_rs485 *rs485);
137 	int			(*iso7816_config)(struct uart_port *,
138 						  struct serial_iso7816 *iso7816);
139 	unsigned int		irq;			/* irq number */
140 	unsigned long		irqflags;		/* irq flags  */
141 	unsigned int		uartclk;		/* base uart clock */
142 	unsigned int		fifosize;		/* tx fifo size */
143 	unsigned char		x_char;			/* xon/xoff char */
144 	unsigned char		regshift;		/* reg offset shift */
145 	unsigned char		iotype;			/* io access style */
146 	unsigned char		quirks;			/* internal quirks */
147 
148 #define UPIO_PORT		(SERIAL_IO_PORT)	/* 8b I/O port access */
149 #define UPIO_HUB6		(SERIAL_IO_HUB6)	/* Hub6 ISA card */
150 #define UPIO_MEM		(SERIAL_IO_MEM)		/* driver-specific */
151 #define UPIO_MEM32		(SERIAL_IO_MEM32)	/* 32b little endian */
152 #define UPIO_AU			(SERIAL_IO_AU)		/* Au1x00 and RT288x type IO */
153 #define UPIO_TSI		(SERIAL_IO_TSI)		/* Tsi108/109 type IO */
154 #define UPIO_MEM32BE		(SERIAL_IO_MEM32BE)	/* 32b big endian */
155 #define UPIO_MEM16		(SERIAL_IO_MEM16)	/* 16b little endian */
156 
157 	/* quirks must be updated while holding port mutex */
158 #define UPQ_NO_TXEN_TEST	BIT(0)
159 
160 	unsigned int		read_status_mask;	/* driver specific */
161 	unsigned int		ignore_status_mask;	/* driver specific */
162 	struct uart_state	*state;			/* pointer to parent state */
163 	struct uart_icount	icount;			/* statistics */
164 
165 	struct console		*cons;			/* struct console, if any */
166 	/* flags must be updated while holding port mutex */
167 	upf_t			flags;
168 
169 	/*
170 	 * These flags must be equivalent to the flags defined in
171 	 * include/uapi/linux/tty_flags.h which are the userspace definitions
172 	 * assigned from the serial_struct flags in uart_set_info()
173 	 * [for bit definitions in the UPF_CHANGE_MASK]
174 	 *
175 	 * Bits [0..ASYNCB_LAST_USER] are userspace defined/visible/changeable
176 	 * The remaining bits are serial-core specific and not modifiable by
177 	 * userspace.
178 	 */
179 #define UPF_FOURPORT		((__force upf_t) ASYNC_FOURPORT       /* 1  */ )
180 #define UPF_SAK			((__force upf_t) ASYNC_SAK            /* 2  */ )
181 #define UPF_SPD_HI		((__force upf_t) ASYNC_SPD_HI         /* 4  */ )
182 #define UPF_SPD_VHI		((__force upf_t) ASYNC_SPD_VHI        /* 5  */ )
183 #define UPF_SPD_CUST		((__force upf_t) ASYNC_SPD_CUST   /* 0x0030 */ )
184 #define UPF_SPD_WARP		((__force upf_t) ASYNC_SPD_WARP   /* 0x1010 */ )
185 #define UPF_SPD_MASK		((__force upf_t) ASYNC_SPD_MASK   /* 0x1030 */ )
186 #define UPF_SKIP_TEST		((__force upf_t) ASYNC_SKIP_TEST      /* 6  */ )
187 #define UPF_AUTO_IRQ		((__force upf_t) ASYNC_AUTO_IRQ       /* 7  */ )
188 #define UPF_HARDPPS_CD		((__force upf_t) ASYNC_HARDPPS_CD     /* 11 */ )
189 #define UPF_SPD_SHI		((__force upf_t) ASYNC_SPD_SHI        /* 12 */ )
190 #define UPF_LOW_LATENCY		((__force upf_t) ASYNC_LOW_LATENCY    /* 13 */ )
191 #define UPF_BUGGY_UART		((__force upf_t) ASYNC_BUGGY_UART     /* 14 */ )
192 #define UPF_MAGIC_MULTIPLIER	((__force upf_t) ASYNC_MAGIC_MULTIPLIER /* 16 */ )
193 
194 #define UPF_NO_THRE_TEST	((__force upf_t) (1 << 19))
195 /* Port has hardware-assisted h/w flow control */
196 #define UPF_AUTO_CTS		((__force upf_t) (1 << 20))
197 #define UPF_AUTO_RTS		((__force upf_t) (1 << 21))
198 #define UPF_HARD_FLOW		((__force upf_t) (UPF_AUTO_CTS | UPF_AUTO_RTS))
199 /* Port has hardware-assisted s/w flow control */
200 #define UPF_SOFT_FLOW		((__force upf_t) (1 << 22))
201 #define UPF_CONS_FLOW		((__force upf_t) (1 << 23))
202 #define UPF_SHARE_IRQ		((__force upf_t) (1 << 24))
203 #define UPF_EXAR_EFR		((__force upf_t) (1 << 25))
204 #define UPF_BUG_THRE		((__force upf_t) (1 << 26))
205 /* The exact UART type is known and should not be probed.  */
206 #define UPF_FIXED_TYPE		((__force upf_t) (1 << 27))
207 #define UPF_BOOT_AUTOCONF	((__force upf_t) (1 << 28))
208 #define UPF_FIXED_PORT		((__force upf_t) (1 << 29))
209 #define UPF_DEAD		((__force upf_t) (1 << 30))
210 #define UPF_IOREMAP		((__force upf_t) (1 << 31))
211 
212 #define __UPF_CHANGE_MASK	0x17fff
213 #define UPF_CHANGE_MASK		((__force upf_t) __UPF_CHANGE_MASK)
214 #define UPF_USR_MASK		((__force upf_t) (UPF_SPD_MASK|UPF_LOW_LATENCY))
215 
216 #if __UPF_CHANGE_MASK > ASYNC_FLAGS
217 #error Change mask not equivalent to userspace-visible bit defines
218 #endif
219 
220 	/*
221 	 * Must hold termios_rwsem, port mutex and port lock to change;
222 	 * can hold any one lock to read.
223 	 */
224 	upstat_t		status;
225 
226 #define UPSTAT_CTS_ENABLE	((__force upstat_t) (1 << 0))
227 #define UPSTAT_DCD_ENABLE	((__force upstat_t) (1 << 1))
228 #define UPSTAT_AUTORTS		((__force upstat_t) (1 << 2))
229 #define UPSTAT_AUTOCTS		((__force upstat_t) (1 << 3))
230 #define UPSTAT_AUTOXOFF		((__force upstat_t) (1 << 4))
231 #define UPSTAT_SYNC_FIFO	((__force upstat_t) (1 << 5))
232 
233 	int			hw_stopped;		/* sw-assisted CTS flow state */
234 	unsigned int		mctrl;			/* current modem ctrl settings */
235 	unsigned int		frame_time;		/* frame timing in ns */
236 	unsigned int		type;			/* port type */
237 	const struct uart_ops	*ops;
238 	unsigned int		custom_divisor;
239 	unsigned int		line;			/* port index */
240 	unsigned int		minor;
241 	resource_size_t		mapbase;		/* for ioremap */
242 	resource_size_t		mapsize;
243 	struct device		*dev;			/* parent device */
244 
245 	unsigned long		sysrq;			/* sysrq timeout */
246 	unsigned int		sysrq_ch;		/* char for sysrq */
247 	unsigned char		has_sysrq;
248 	unsigned char		sysrq_seq;		/* index in sysrq_toggle_seq */
249 
250 	unsigned char		hub6;			/* this should be in the 8250 driver */
251 	unsigned char		suspended;
252 	unsigned char		console_reinit;
253 	const char		*name;			/* port name */
254 	struct attribute_group	*attr_group;		/* port specific attributes */
255 	const struct attribute_group **tty_groups;	/* all attributes (serial core use only) */
256 	struct serial_rs485     rs485;
257 	const struct serial_rs485	*rs485_supported;	/* Supported mask for serial_rs485 */
258 	struct gpio_desc	*rs485_term_gpio;	/* enable RS485 bus termination */
259 	struct serial_iso7816   iso7816;
260 	void			*private_data;		/* generic platform data pointer */
261 };
262 
263 static inline int serial_port_in(struct uart_port *up, int offset)
264 {
265 	return up->serial_in(up, offset);
266 }
267 
268 static inline void serial_port_out(struct uart_port *up, int offset, int value)
269 {
270 	up->serial_out(up, offset, value);
271 }
272 
273 /**
274  * enum uart_pm_state - power states for UARTs
275  * @UART_PM_STATE_ON: UART is powered, up and operational
276  * @UART_PM_STATE_OFF: UART is powered off
277  * @UART_PM_STATE_UNDEFINED: sentinel
278  */
279 enum uart_pm_state {
280 	UART_PM_STATE_ON = 0,
281 	UART_PM_STATE_OFF = 3, /* number taken from ACPI */
282 	UART_PM_STATE_UNDEFINED,
283 };
284 
285 /*
286  * This is the state information which is persistent across opens.
287  */
288 struct uart_state {
289 	struct tty_port		port;
290 
291 	enum uart_pm_state	pm_state;
292 	struct circ_buf		xmit;
293 
294 	atomic_t		refcount;
295 	wait_queue_head_t	remove_wait;
296 	struct uart_port	*uart_port;
297 };
298 
299 #define UART_XMIT_SIZE	PAGE_SIZE
300 
301 
302 /* number of characters left in xmit buffer before we ask for more */
303 #define WAKEUP_CHARS		256
304 
305 struct module;
306 struct tty_driver;
307 
308 struct uart_driver {
309 	struct module		*owner;
310 	const char		*driver_name;
311 	const char		*dev_name;
312 	int			 major;
313 	int			 minor;
314 	int			 nr;
315 	struct console		*cons;
316 
317 	/*
318 	 * these are private; the low level driver should not
319 	 * touch these; they should be initialised to NULL
320 	 */
321 	struct uart_state	*state;
322 	struct tty_driver	*tty_driver;
323 };
324 
325 void uart_write_wakeup(struct uart_port *port);
326 
327 /*
328  * Baud rate helpers.
329  */
330 void uart_update_timeout(struct uart_port *port, unsigned int cflag,
331 			 unsigned int baud);
332 unsigned int uart_get_baud_rate(struct uart_port *port, struct ktermios *termios,
333 				struct ktermios *old, unsigned int min,
334 				unsigned int max);
335 unsigned int uart_get_divisor(struct uart_port *port, unsigned int baud);
336 
337 /*
338  * Calculates FIFO drain time.
339  */
340 static inline unsigned long uart_fifo_timeout(struct uart_port *port)
341 {
342 	u64 fifo_timeout = (u64)READ_ONCE(port->frame_time) * port->fifosize;
343 
344 	/* Add .02 seconds of slop */
345 	fifo_timeout += 20 * NSEC_PER_MSEC;
346 
347 	return max(nsecs_to_jiffies(fifo_timeout), 1UL);
348 }
349 
350 /* Base timer interval for polling */
351 static inline int uart_poll_timeout(struct uart_port *port)
352 {
353 	int timeout = uart_fifo_timeout(port);
354 
355 	return timeout > 6 ? (timeout / 2 - 2) : 1;
356 }
357 
358 /*
359  * Console helpers.
360  */
361 struct earlycon_device {
362 	struct console *con;
363 	struct uart_port port;
364 	char options[16];		/* e.g., 115200n8 */
365 	unsigned int baud;
366 };
367 
368 struct earlycon_id {
369 	char	name[15];
370 	char	name_term;	/* In case compiler didn't '\0' term name */
371 	char	compatible[128];
372 	int	(*setup)(struct earlycon_device *, const char *options);
373 };
374 
375 extern const struct earlycon_id __earlycon_table[];
376 extern const struct earlycon_id __earlycon_table_end[];
377 
378 #if defined(CONFIG_SERIAL_EARLYCON) && !defined(MODULE)
379 #define EARLYCON_USED_OR_UNUSED	__used
380 #else
381 #define EARLYCON_USED_OR_UNUSED	__maybe_unused
382 #endif
383 
384 #define OF_EARLYCON_DECLARE(_name, compat, fn)				\
385 	static const struct earlycon_id __UNIQUE_ID(__earlycon_##_name) \
386 		EARLYCON_USED_OR_UNUSED  __section("__earlycon_table")  \
387 		__aligned(__alignof__(struct earlycon_id))		\
388 		= { .name = __stringify(_name),				\
389 		    .compatible = compat,				\
390 		    .setup = fn }
391 
392 #define EARLYCON_DECLARE(_name, fn)	OF_EARLYCON_DECLARE(_name, "", fn)
393 
394 extern int of_setup_earlycon(const struct earlycon_id *match,
395 			     unsigned long node,
396 			     const char *options);
397 
398 #ifdef CONFIG_SERIAL_EARLYCON
399 extern bool earlycon_acpi_spcr_enable __initdata;
400 int setup_earlycon(char *buf);
401 #else
402 static const bool earlycon_acpi_spcr_enable EARLYCON_USED_OR_UNUSED;
403 static inline int setup_earlycon(char *buf) { return 0; }
404 #endif
405 
406 struct uart_port *uart_get_console(struct uart_port *ports, int nr,
407 				   struct console *c);
408 int uart_parse_earlycon(char *p, unsigned char *iotype, resource_size_t *addr,
409 			char **options);
410 void uart_parse_options(const char *options, int *baud, int *parity, int *bits,
411 			int *flow);
412 int uart_set_options(struct uart_port *port, struct console *co, int baud,
413 		     int parity, int bits, int flow);
414 struct tty_driver *uart_console_device(struct console *co, int *index);
415 void uart_console_write(struct uart_port *port, const char *s,
416 			unsigned int count,
417 			void (*putchar)(struct uart_port *, unsigned char));
418 
419 /*
420  * Port/driver registration/removal
421  */
422 int uart_register_driver(struct uart_driver *uart);
423 void uart_unregister_driver(struct uart_driver *uart);
424 int uart_add_one_port(struct uart_driver *reg, struct uart_port *port);
425 int uart_remove_one_port(struct uart_driver *reg, struct uart_port *port);
426 bool uart_match_port(const struct uart_port *port1,
427 		const struct uart_port *port2);
428 
429 /*
430  * Power Management
431  */
432 int uart_suspend_port(struct uart_driver *reg, struct uart_port *port);
433 int uart_resume_port(struct uart_driver *reg, struct uart_port *port);
434 
435 #define uart_circ_empty(circ)		((circ)->head == (circ)->tail)
436 #define uart_circ_clear(circ)		((circ)->head = (circ)->tail = 0)
437 
438 #define uart_circ_chars_pending(circ)	\
439 	(CIRC_CNT((circ)->head, (circ)->tail, UART_XMIT_SIZE))
440 
441 #define uart_circ_chars_free(circ)	\
442 	(CIRC_SPACE((circ)->head, (circ)->tail, UART_XMIT_SIZE))
443 
444 static inline int uart_tx_stopped(struct uart_port *port)
445 {
446 	struct tty_struct *tty = port->state->port.tty;
447 	if ((tty && tty->flow.stopped) || port->hw_stopped)
448 		return 1;
449 	return 0;
450 }
451 
452 static inline bool uart_cts_enabled(struct uart_port *uport)
453 {
454 	return !!(uport->status & UPSTAT_CTS_ENABLE);
455 }
456 
457 static inline bool uart_softcts_mode(struct uart_port *uport)
458 {
459 	upstat_t mask = UPSTAT_CTS_ENABLE | UPSTAT_AUTOCTS;
460 
461 	return ((uport->status & mask) == UPSTAT_CTS_ENABLE);
462 }
463 
464 /*
465  * The following are helper functions for the low level drivers.
466  */
467 
468 extern void uart_handle_dcd_change(struct uart_port *uport,
469 		unsigned int status);
470 extern void uart_handle_cts_change(struct uart_port *uport,
471 		unsigned int status);
472 
473 extern void uart_insert_char(struct uart_port *port, unsigned int status,
474 		 unsigned int overrun, unsigned int ch, unsigned int flag);
475 
476 void uart_xchar_out(struct uart_port *uport, int offset);
477 
478 #ifdef CONFIG_MAGIC_SYSRQ_SERIAL
479 #define SYSRQ_TIMEOUT	(HZ * 5)
480 
481 bool uart_try_toggle_sysrq(struct uart_port *port, unsigned int ch);
482 
483 static inline int uart_handle_sysrq_char(struct uart_port *port, unsigned int ch)
484 {
485 	if (!port->sysrq)
486 		return 0;
487 
488 	if (ch && time_before(jiffies, port->sysrq)) {
489 		if (sysrq_mask()) {
490 			handle_sysrq(ch);
491 			port->sysrq = 0;
492 			return 1;
493 		}
494 		if (uart_try_toggle_sysrq(port, ch))
495 			return 1;
496 	}
497 	port->sysrq = 0;
498 
499 	return 0;
500 }
501 
502 static inline int uart_prepare_sysrq_char(struct uart_port *port, unsigned int ch)
503 {
504 	if (!port->sysrq)
505 		return 0;
506 
507 	if (ch && time_before(jiffies, port->sysrq)) {
508 		if (sysrq_mask()) {
509 			port->sysrq_ch = ch;
510 			port->sysrq = 0;
511 			return 1;
512 		}
513 		if (uart_try_toggle_sysrq(port, ch))
514 			return 1;
515 	}
516 	port->sysrq = 0;
517 
518 	return 0;
519 }
520 
521 static inline void uart_unlock_and_check_sysrq(struct uart_port *port)
522 {
523 	int sysrq_ch;
524 
525 	if (!port->has_sysrq) {
526 		spin_unlock(&port->lock);
527 		return;
528 	}
529 
530 	sysrq_ch = port->sysrq_ch;
531 	port->sysrq_ch = 0;
532 
533 	spin_unlock(&port->lock);
534 
535 	if (sysrq_ch)
536 		handle_sysrq(sysrq_ch);
537 }
538 
539 static inline void uart_unlock_and_check_sysrq_irqrestore(struct uart_port *port,
540 		unsigned long flags)
541 {
542 	int sysrq_ch;
543 
544 	if (!port->has_sysrq) {
545 		spin_unlock_irqrestore(&port->lock, flags);
546 		return;
547 	}
548 
549 	sysrq_ch = port->sysrq_ch;
550 	port->sysrq_ch = 0;
551 
552 	spin_unlock_irqrestore(&port->lock, flags);
553 
554 	if (sysrq_ch)
555 		handle_sysrq(sysrq_ch);
556 }
557 #else	/* CONFIG_MAGIC_SYSRQ_SERIAL */
558 static inline int uart_handle_sysrq_char(struct uart_port *port, unsigned int ch)
559 {
560 	return 0;
561 }
562 static inline int uart_prepare_sysrq_char(struct uart_port *port, unsigned int ch)
563 {
564 	return 0;
565 }
566 static inline void uart_unlock_and_check_sysrq(struct uart_port *port)
567 {
568 	spin_unlock(&port->lock);
569 }
570 static inline void uart_unlock_and_check_sysrq_irqrestore(struct uart_port *port,
571 		unsigned long flags)
572 {
573 	spin_unlock_irqrestore(&port->lock, flags);
574 }
575 #endif	/* CONFIG_MAGIC_SYSRQ_SERIAL */
576 
577 /*
578  * We do the SysRQ and SAK checking like this...
579  */
580 static inline int uart_handle_break(struct uart_port *port)
581 {
582 	struct uart_state *state = port->state;
583 
584 	if (port->handle_break)
585 		port->handle_break(port);
586 
587 #ifdef CONFIG_MAGIC_SYSRQ_SERIAL
588 	if (port->has_sysrq && uart_console(port)) {
589 		if (!port->sysrq) {
590 			port->sysrq = jiffies + SYSRQ_TIMEOUT;
591 			return 1;
592 		}
593 		port->sysrq = 0;
594 	}
595 #endif
596 	if (port->flags & UPF_SAK)
597 		do_SAK(state->port.tty);
598 	return 0;
599 }
600 
601 /*
602  *	UART_ENABLE_MS - determine if port should enable modem status irqs
603  */
604 #define UART_ENABLE_MS(port,cflag)	((port)->flags & UPF_HARDPPS_CD || \
605 					 (cflag) & CRTSCTS || \
606 					 !((cflag) & CLOCAL))
607 
608 int uart_get_rs485_mode(struct uart_port *port);
609 int uart_rs485_config(struct uart_port *port);
610 #endif /* LINUX_SERIAL_CORE_H */
611