aboutsummaryrefslogtreecommitdiff
path: root/sys/dev/nmdm/nmdm.c
blob: 74b5c1203596b94f0dd45be01ccb6620e132f0d1 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1982, 1986, 1989, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

/*
 * Pseudo-nulmodem driver
 * Mighty handy for use with serial console in Vmware
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/tty.h>
#include <sys/conf.h>
#include <sys/fcntl.h>
#include <sys/poll.h>
#include <sys/kernel.h>
#include <sys/limits.h>
#include <sys/module.h>
#include <sys/serial.h>
#include <sys/signalvar.h>
#include <sys/malloc.h>
#include <sys/taskqueue.h>

static MALLOC_DEFINE(M_NMDM, "nullmodem", "nullmodem data structures");

static tsw_inwakeup_t	nmdm_outwakeup;
static tsw_outwakeup_t	nmdm_inwakeup;
static tsw_param_t	nmdm_param;
static tsw_modem_t	nmdm_modem;
static tsw_close_t	nmdm_close;
static tsw_free_t	nmdm_free;

static struct ttydevsw nmdm_class = {
	.tsw_flags	= TF_NOPREFIX,
	.tsw_inwakeup	= nmdm_inwakeup,
	.tsw_outwakeup	= nmdm_outwakeup,
	.tsw_param	= nmdm_param,
	.tsw_modem	= nmdm_modem,
	.tsw_close	= nmdm_close,
	.tsw_free	= nmdm_free,
};

static void nmdm_task_tty(void *, int);

struct nmdmsoftc;

struct nmdmpart {
	struct tty		*np_tty;
	int			 np_dcd;
	struct task		 np_task;
	struct nmdmpart		*np_other;
	struct nmdmsoftc	*np_pair;
	struct callout		 np_callout;
	u_long			 np_quota;
	u_long			 np_accumulator;
	int			 np_rate;
	int			 np_credits;

#define QS 8	/* Quota shift */
};

struct nmdmsoftc {
	struct nmdmpart	ns_part1;
	struct nmdmpart	ns_part2;
	struct mtx	ns_mtx;
};

static int nmdm_count = 0;

static void
nmdm_close(struct tty *tp)
{
	struct nmdmpart *np;
	struct nmdmpart *onp;
	struct tty *otp;

	np = tty_softc(tp);
	onp = np->np_other;
	otp = onp->np_tty;

	/* If second part is opened, do not destroy ourselves. */
	if (tty_opened(otp))
		return;

	/* Shut down self. */
	tty_rel_gone(tp);

	/* Shut down second part. */
	tty_lock(tp);
	onp = np->np_other;
	if (onp == NULL)
		return;
	otp = onp->np_tty;
	tty_rel_gone(otp);
	tty_lock(tp);
}

static void
nmdm_free(void *softc)
{
	struct nmdmpart *np = (struct nmdmpart *)softc;
	struct nmdmsoftc *ns = np->np_pair;

	callout_drain(&np->np_callout);
	taskqueue_drain(taskqueue_swi, &np->np_task);

	/*
	 * The function is called on both parts simultaneously.  We serialize
	 * with help of ns_mtx.  The first invocation should return and
	 * delegate freeing of resources to the second.
	 */
	mtx_lock(&ns->ns_mtx);
	if (np->np_other != NULL) {
		np->np_other->np_other = NULL;
		mtx_unlock(&ns->ns_mtx);
		return;
	}
	mtx_destroy(&ns->ns_mtx);
	free(ns, M_NMDM);
	atomic_subtract_int(&nmdm_count, 1);
}

static void
nmdm_clone(void *arg, struct ucred *cred, char *name, int nameen,
    struct cdev **dev)
{
	struct nmdmsoftc *ns;
	struct tty *tp;
	char *end;
	int error;
	char endc;

	if (*dev != NULL)
		return;
	if (strncmp(name, "nmdm", 4) != 0)
		return;
	if (strlen(name) <= strlen("nmdmX"))
		return;

	/* Device name must be "nmdm%s%c", where %c is 'A' or 'B'. */
	end = name + strlen(name) - 1;
	endc = *end;
	if (endc != 'A' && endc != 'B')
		return;

	ns = malloc(sizeof(*ns), M_NMDM, M_WAITOK | M_ZERO);
	mtx_init(&ns->ns_mtx, "nmdm", NULL, MTX_DEF);

	/* Hook the pairs together. */
	ns->ns_part1.np_pair = ns;
	ns->ns_part1.np_other = &ns->ns_part2;
	TASK_INIT(&ns->ns_part1.np_task, 0, nmdm_task_tty, &ns->ns_part1);
	callout_init_mtx(&ns->ns_part1.np_callout, &ns->ns_mtx, 0);

	ns->ns_part2.np_pair = ns;
	ns->ns_part2.np_other = &ns->ns_part1;
	TASK_INIT(&ns->ns_part2.np_task, 0, nmdm_task_tty, &ns->ns_part2);
	callout_init_mtx(&ns->ns_part2.np_callout, &ns->ns_mtx, 0);

	/* Create device nodes. */
	tp = ns->ns_part1.np_tty = tty_alloc_mutex(&nmdm_class, &ns->ns_part1,
	    &ns->ns_mtx);
	*end = 'A';
	error = tty_makedevf(tp, NULL, endc == 'A' ? TTYMK_CLONING : 0,
	    "%s", name);
	if (error) {
		*end = endc;
		mtx_destroy(&ns->ns_mtx);
		free(ns, M_NMDM);
		return;
	}

	tp = ns->ns_part2.np_tty = tty_alloc_mutex(&nmdm_class, &ns->ns_part2,
	    &ns->ns_mtx);
	*end = 'B';
	error = tty_makedevf(tp, NULL, endc == 'B' ? TTYMK_CLONING : 0,
	    "%s", name);
	if (error) {
		*end = endc;
		mtx_lock(&ns->ns_mtx);
		/* see nmdm_free() */
		ns->ns_part1.np_other = NULL;
		atomic_add_int(&nmdm_count, 1);
		tty_rel_gone(ns->ns_part1.np_tty);
		return;
	}

	if (endc == 'A')
		*dev = ns->ns_part1.np_tty->t_dev;
	else
		*dev = ns->ns_part2.np_tty->t_dev;

	*end = endc;
	atomic_add_int(&nmdm_count, 1);
}

static void
nmdm_timeout(void *arg)
{
	struct nmdmpart *np = arg;

	if (np->np_rate == 0)
		return;

	/*
	 * Do a simple Floyd-Steinberg dither here to avoid FP math.
	 * Wipe out unused quota from last tick.
	 */
	np->np_accumulator += np->np_credits;
	np->np_quota = np->np_accumulator >> QS;
	np->np_accumulator &= ((1 << QS) - 1);

	taskqueue_enqueue(taskqueue_swi, &np->np_task);
	callout_reset(&np->np_callout, np->np_rate, nmdm_timeout, np);
}

static void
nmdm_task_tty(void *arg, int pending __unused)
{
	struct tty *tp, *otp;
	struct nmdmpart *np = arg;
	char c;

	tp = np->np_tty;
	tty_lock(tp);
	if (tty_gone(tp)) {
		tty_unlock(tp);
		return;
	}

	otp = np->np_other->np_tty;
	KASSERT(otp != NULL, ("NULL otp in nmdmstart"));
	KASSERT(otp != tp, ("NULL otp == tp nmdmstart"));
	if (np->np_other->np_dcd) {
		if (!tty_opened(tp)) {
			np->np_other->np_dcd = 0;
			ttydisc_modem(otp, 0);
		}
	} else {
		if (tty_opened(tp)) {
			np->np_other->np_dcd = 1;
			ttydisc_modem(otp, 1);
		}
	}

	/* This may happen when we are in detach process. */
	if (tty_gone(otp)) {
		tty_unlock(otp);
		return;
	}

	while (ttydisc_rint_poll(otp) > 0) {
		if (np->np_rate && !np->np_quota)
			break;
		if (ttydisc_getc(tp, &c, 1) != 1)
			break;
		np->np_quota--;
		ttydisc_rint(otp, c, 0);
	}

	ttydisc_rint_done(otp);

	tty_unlock(tp);
}

static int
bits_per_char(struct termios *t)
{
	int bits;

	bits = 1;		/* start bit */
	switch (t->c_cflag & CSIZE) {
	case CS5:	bits += 5;	break;
	case CS6:	bits += 6;	break;
	case CS7:	bits += 7;	break;
	case CS8:	bits += 8;	break;
	}
	bits++;			/* stop bit */
	if (t->c_cflag & PARENB)
		bits++;
	if (t->c_cflag & CSTOPB)
		bits++;
	return (bits);
}

static int
nmdm_param(struct tty *tp, struct termios *t)
{
	struct nmdmpart *np = tty_softc(tp);
	struct tty *tp2;
	int bpc, rate, speed, i;

	tp2 = np->np_other->np_tty;

	if (!((t->c_cflag | tp2->t_termios.c_cflag) & CDSR_OFLOW)) {
		np->np_rate = 0;
		np->np_other->np_rate = 0;
		return (0);
	}

	/*
	 * DSRFLOW one either side enables rate-simulation for both
	 * directions.
	 * NB: the two directions may run at different rates.
	 */

	/* Find the larger of the number of bits transmitted */
	bpc = imax(bits_per_char(t), bits_per_char(&tp2->t_termios));

	for (i = 0; i < 2; i++) {
		/* Use the slower of our receive and their transmit rate */
		speed = imin(tp2->t_termios.c_ospeed, t->c_ispeed);
		if (speed == 0) {
			np->np_rate = 0;
			np->np_other->np_rate = 0;
			return (0);
		}

		speed <<= QS;			/* [bit/sec, scaled] */
		speed /= bpc;			/* [char/sec, scaled] */
		rate = (hz << QS) / speed;	/* [hz per callout] */
		if (rate == 0)
			rate = 1;

		speed *= rate;
		speed /= hz;			/* [(char/sec)/tick, scaled */

		np->np_credits = speed;
		np->np_rate = rate;
		callout_reset(&np->np_callout, rate, nmdm_timeout, np);

		/*
		 * swap pointers for second pass so the other end gets
		 * updated as well.
		 */
		np = np->np_other;
		t = &tp2->t_termios;
		tp2 = tp;
	}

	return (0);
}

static int
nmdm_modem(struct tty *tp, int sigon, int sigoff)
{
	struct nmdmpart *np = tty_softc(tp);
	int i = 0;

	if (sigon || sigoff) {
		if (sigon & SER_DTR)
			np->np_other->np_dcd = 1;
		if (sigoff & SER_DTR)
			np->np_other->np_dcd = 0;

		ttydisc_modem(np->np_other->np_tty, np->np_other->np_dcd);

		return (0);
	} else {
		if (np->np_dcd)
			i |= SER_DCD;
		if (np->np_other->np_dcd)
			i |= SER_DTR;

		return (i);
	}
}

static void
nmdm_inwakeup(struct tty *tp)
{
	struct nmdmpart *np = tty_softc(tp);

	/* We can receive again, so wake up the other side. */
	taskqueue_enqueue(taskqueue_swi, &np->np_other->np_task);
}

static void
nmdm_outwakeup(struct tty *tp)
{
	struct nmdmpart *np = tty_softc(tp);

	/* We can transmit again, so wake up our side. */
	taskqueue_enqueue(taskqueue_swi, &np->np_task);
}

/*
 * Module handling
 */
static int
nmdm_modevent(module_t mod, int type, void *data)
{
	static eventhandler_tag tag;

        switch(type) {
        case MOD_LOAD: 
		tag = EVENTHANDLER_REGISTER(dev_clone, nmdm_clone, 0, 1000);
		if (tag == NULL)
			return (ENOMEM);
		break;

	case MOD_SHUTDOWN:
		break;

	case MOD_UNLOAD:
		if (nmdm_count != 0)
			return (EBUSY);
		EVENTHANDLER_DEREGISTER(dev_clone, tag);
		break;

	default:
		return (EOPNOTSUPP);
	}

	return (0);
}

DEV_MODULE(nmdm, nmdm_modevent, NULL);