1// SPDX-License-Identifier: GPL-2.0
2/*
3 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
4 */
5
6#include <linux/types.h>
7#include <linux/kernel.h>
8#include <linux/termios.h>
9#include <linux/tty.h>
10#include <linux/export.h>
11#include "tty.h"
12
13
14/*
15 * Routine which returns the baud rate of the tty
16 *
17 * Note that the baud_table needs to be kept in sync with the
18 * include/asm/termbits.h file.
19 */
20static const speed_t baud_table[] = {
21	0, 50, 75, 110, 134, 150, 200, 300, 600, 1200, 1800, 2400,
22	4800, 9600, 19200, 38400, 57600, 115200, 230400, 460800,
23#ifdef __sparc__
24	76800, 153600, 307200, 614400, 921600, 500000, 576000,
25	1000000, 1152000, 1500000, 2000000
26#else
27	500000, 576000, 921600, 1000000, 1152000, 1500000, 2000000,
28	2500000, 3000000, 3500000, 4000000
29#endif
30};
31
32static const tcflag_t baud_bits[] = {
33	B0, B50, B75, B110, B134, B150, B200, B300, B600, B1200, B1800, B2400,
34	B4800, B9600, B19200, B38400, B57600, B115200, B230400, B460800,
35#ifdef __sparc__
36	B76800, B153600, B307200, B614400, B921600, B500000, B576000,
37	B1000000, B1152000, B1500000, B2000000
38#else
39	B500000, B576000, B921600, B1000000, B1152000, B1500000, B2000000,
40	B2500000, B3000000, B3500000, B4000000
41#endif
42};
43
44static int n_baud_table = ARRAY_SIZE(baud_table);
45
46/**
47 *	tty_termios_baud_rate
48 *	@termios: termios structure
49 *
50 *	Convert termios baud rate data into a speed. This should be called
51 *	with the termios lock held if this termios is a terminal termios
52 *	structure. May change the termios data. Device drivers can call this
53 *	function but should use ->c_[io]speed directly as they are updated.
54 *
55 *	Locking: none
56 */
57
58speed_t tty_termios_baud_rate(struct ktermios *termios)
59{
60	unsigned int cbaud;
61
62	cbaud = termios->c_cflag & CBAUD;
63
64#ifdef BOTHER
65	/* Magic token for arbitrary speed via c_ispeed/c_ospeed */
66	if (cbaud == BOTHER)
67		return termios->c_ospeed;
68#endif
69	if (cbaud & CBAUDEX) {
70		cbaud &= ~CBAUDEX;
71
72		if (cbaud < 1 || cbaud + 15 > n_baud_table)
73			termios->c_cflag &= ~CBAUDEX;
74		else
75			cbaud += 15;
76	}
77	return cbaud >= n_baud_table ? 0 : baud_table[cbaud];
78}
79EXPORT_SYMBOL(tty_termios_baud_rate);
80
81/**
82 *	tty_termios_input_baud_rate
83 *	@termios: termios structure
84 *
85 *	Convert termios baud rate data into a speed. This should be called
86 *	with the termios lock held if this termios is a terminal termios
87 *	structure. May change the termios data. Device drivers can call this
88 *	function but should use ->c_[io]speed directly as they are updated.
89 *
90 *	Locking: none
91 */
92
93speed_t tty_termios_input_baud_rate(struct ktermios *termios)
94{
95#ifdef IBSHIFT
96	unsigned int cbaud = (termios->c_cflag >> IBSHIFT) & CBAUD;
97
98	if (cbaud == B0)
99		return tty_termios_baud_rate(termios);
100#ifdef BOTHER
101	/* Magic token for arbitrary speed via c_ispeed*/
102	if (cbaud == BOTHER)
103		return termios->c_ispeed;
104#endif
105	if (cbaud & CBAUDEX) {
106		cbaud &= ~CBAUDEX;
107
108		if (cbaud < 1 || cbaud + 15 > n_baud_table)
109			termios->c_cflag &= ~(CBAUDEX << IBSHIFT);
110		else
111			cbaud += 15;
112	}
113	return cbaud >= n_baud_table ? 0 : baud_table[cbaud];
114#else	/* IBSHIFT */
115	return tty_termios_baud_rate(termios);
116#endif	/* IBSHIFT */
117}
118EXPORT_SYMBOL(tty_termios_input_baud_rate);
119
120/**
121 *	tty_termios_encode_baud_rate
122 *	@termios: ktermios structure holding user requested state
123 *	@ibaud: input speed
124 *	@obaud: output speed
125 *
126 *	Encode the speeds set into the passed termios structure. This is
127 *	used as a library helper for drivers so that they can report back
128 *	the actual speed selected when it differs from the speed requested
129 *
130 *	For maximal back compatibility with legacy SYS5/POSIX *nix behaviour
131 *	we need to carefully set the bits when the user does not get the
132 *	desired speed. We allow small margins and preserve as much of possible
133 *	of the input intent to keep compatibility.
134 *
135 *	Locking: Caller should hold termios lock. This is already held
136 *	when calling this function from the driver termios handler.
137 *
138 *	The ifdefs deal with platforms whose owners have yet to update them
139 *	and will all go away once this is done.
140 */
141
142void tty_termios_encode_baud_rate(struct ktermios *termios,
143				  speed_t ibaud, speed_t obaud)
144{
145	int i = 0;
146	int ifound = -1, ofound = -1;
147	int iclose = ibaud/50, oclose = obaud/50;
148	int ibinput = 0;
149
150	if (obaud == 0)			/* CD dropped 		  */
151		ibaud = 0;		/* Clear ibaud to be sure */
152
153	termios->c_ispeed = ibaud;
154	termios->c_ospeed = obaud;
155
156#ifdef IBSHIFT
157	if ((termios->c_cflag >> IBSHIFT) & CBAUD)
158		ibinput = 1;	/* An input speed was specified */
159#endif
160#ifdef BOTHER
161	/* If the user asked for a precise weird speed give a precise weird
162	   answer. If they asked for a Bfoo speed they may have problems
163	   digesting non-exact replies so fuzz a bit */
164
165	if ((termios->c_cflag & CBAUD) == BOTHER) {
166		oclose = 0;
167		if (!ibinput)
168			iclose = 0;
169	}
170	if (((termios->c_cflag >> IBSHIFT) & CBAUD) == BOTHER)
171		iclose = 0;
172#endif
173	termios->c_cflag &= ~CBAUD;
174#ifdef IBSHIFT
175	termios->c_cflag &= ~(CBAUD << IBSHIFT);
176#endif
177
178	/*
179	 *	Our goal is to find a close match to the standard baud rate
180	 *	returned. Walk the baud rate table and if we get a very close
181	 *	match then report back the speed as a POSIX Bxxxx value by
182	 *	preference
183	 */
184
185	do {
186		if (obaud - oclose <= baud_table[i] &&
187		    obaud + oclose >= baud_table[i]) {
188			termios->c_cflag |= baud_bits[i];
189			ofound = i;
190		}
191		if (ibaud - iclose <= baud_table[i] &&
192		    ibaud + iclose >= baud_table[i]) {
193			/* For the case input == output don't set IBAUD bits
194			   if the user didn't do so */
195			if (ofound == i && !ibinput)
196				ifound  = i;
197#ifdef IBSHIFT
198			else {
199				ifound = i;
200				termios->c_cflag |= (baud_bits[i] << IBSHIFT);
201			}
202#endif
203		}
204	} while (++i < n_baud_table);
205
206	/*
207	 *	If we found no match then use BOTHER if provided or warn
208	 *	the user their platform maintainer needs to wake up if not.
209	 */
210#ifdef BOTHER
211	if (ofound == -1)
212		termios->c_cflag |= BOTHER;
213	/* Set exact input bits only if the input and output differ or the
214	   user already did */
215	if (ifound == -1 && (ibaud != obaud || ibinput))
216		termios->c_cflag |= (BOTHER << IBSHIFT);
217#else
218	if (ifound == -1 || ofound == -1)
219		pr_warn_once("tty: Unable to return correct speed data as your architecture needs updating.\n");
220#endif
221}
222EXPORT_SYMBOL_GPL(tty_termios_encode_baud_rate);
223
224/**
225 *	tty_encode_baud_rate		-	set baud rate of the tty
226 *	@ibaud: input baud rate
227 *	@obaud: output baud rate
228 *
229 *	Update the current termios data for the tty with the new speed
230 *	settings. The caller must hold the termios_rwsem for the tty in
231 *	question.
232 */
233
234void tty_encode_baud_rate(struct tty_struct *tty, speed_t ibaud, speed_t obaud)
235{
236	tty_termios_encode_baud_rate(&tty->termios, ibaud, obaud);
237}
238EXPORT_SYMBOL_GPL(tty_encode_baud_rate);
239