sys/dev/nmdm/nmdm.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-3-Clause
   3  *
   4  * Copyright (c) 1982, 1986, 1989, 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. Neither the name of the University nor the names of its contributors
  16  *    may be used to endorse or promote products derived from this software
  17  *    without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  *
  31  */
  32
  33 #include <sys/cdefs.h>
  34 __FBSDID("$FreeBSD$");
  35
  36 /*
  37  * Pseudo-nulmodem driver
  38  * Mighty handy for use with serial console in Vmware
  39  */
  40
  41 #include <sys/param.h>
  42 #include <sys/systm.h>
  43 #include <sys/priv.h>
  44 #include <sys/proc.h>
  45 #include <sys/tty.h>
  46 #include <sys/conf.h>
  47 #include <sys/fcntl.h>
  48 #include <sys/poll.h>
  49 #include <sys/kernel.h>
  50 #include <sys/limits.h>
  51 #include <sys/module.h>
  52 #include <sys/serial.h>
  53 #include <sys/signalvar.h>
  54 #include <sys/malloc.h>
  55 #include <sys/taskqueue.h>
  56
  57 static MALLOC_DEFINE(M_NMDM, "nullmodem", "nullmodem data structures");
  58
  59 static tsw_inwakeup_t   nmdm_outwakeup;
  60 static tsw_outwakeup_t  nmdm_inwakeup;
  61 static tsw_param_t      nmdm_param;
  62 static tsw_modem_t      nmdm_modem;
  63 static tsw_close_t      nmdm_close;
  64 static tsw_free_t       nmdm_free;
  65
  66 static struct ttydevsw nmdm_class = {
  67         .tsw_flags      = TF_NOPREFIX,
  68         .tsw_inwakeup   = nmdm_inwakeup,
  69         .tsw_outwakeup  = nmdm_outwakeup,
  70         .tsw_param      = nmdm_param,
  71         .tsw_modem      = nmdm_modem,
  72         .tsw_close      = nmdm_close,
  73         .tsw_free       = nmdm_free,
  74 };
  75
  76 static void nmdm_task_tty(void *, int);
  77
  78 struct nmdmsoftc;
  79
  80 struct nmdmpart {
  81         struct tty              *np_tty;
  82         int                      np_dcd;
  83         struct task              np_task;
  84         struct nmdmpart         *np_other;
  85         struct nmdmsoftc        *np_pair;
  86         struct callout           np_callout;
  87         u_long                   np_quota;
  88         u_long                   np_accumulator;
  89         int                      np_rate;
  90         int                      np_credits;
  91
  92 #define QS 8    /* Quota shift */
  93 };
  94
  95 struct nmdmsoftc {
  96         struct nmdmpart ns_part1;
  97         struct nmdmpart ns_part2;
  98         struct mtx      ns_mtx;
  99 };
 100
 101 static int nmdm_count = 0;
 102
 103 static void
 104 nmdm_close(struct tty *tp)
 105 {
 106         struct nmdmpart *np;
 107         struct nmdmpart *onp;
 108         struct tty *otp;
 109
 110         np = tty_softc(tp);
 111         onp = np->np_other;
 112         otp = onp->np_tty;
 113
 114         /* If second part is opened, do not destroy ourselves. */
 115         if (tty_opened(otp))
 116                 return;
 117
 118         /* Shut down self. */
 119         tty_rel_gone(tp);
 120
 121         /* Shut down second part. */
 122         tty_lock(tp);
 123         onp = np->np_other;
 124         if (onp == NULL)
 125                 return;
 126         otp = onp->np_tty;
 127         tty_rel_gone(otp);
 128         tty_lock(tp);
 129 }
 130
 131 static void
 132 nmdm_free(void *softc)
 133 {
 134         struct nmdmpart *np = (struct nmdmpart *)softc;
 135         struct nmdmsoftc *ns = np->np_pair;
 136
 137         callout_drain(&np->np_callout);
 138         taskqueue_drain(taskqueue_swi, &np->np_task);
 139
 140         /*
 141          * The function is called on both parts simultaneously.  We serialize
 142          * with help of ns_mtx.  The first invocation should return and
 143          * delegate freeing of resources to the second.
 144          */
 145         mtx_lock(&ns->ns_mtx);
 146         if (np->np_other != NULL) {
 147                 np->np_other->np_other = NULL;
 148                 mtx_unlock(&ns->ns_mtx);
 149                 return;
 150         }
 151         mtx_destroy(&ns->ns_mtx);
 152         free(ns, M_NMDM);
 153         atomic_subtract_int(&nmdm_count, 1);
 154 }
 155
 156 static void
 157 nmdm_clone(void *arg, struct ucred *cred, char *name, int nameen,
 158     struct cdev **dev)
 159 {
 160         struct nmdmsoftc *ns;
 161         struct tty *tp;
 162         char *end;
 163         int error;
 164         char endc;
 165
 166         if (*dev != NULL)
 167                 return;
 168         if (strncmp(name, "nmdm", 4) != 0)
 169                 return;
 170         if (strlen(name) <= strlen("nmdmX"))
 171                 return;
 172
 173         /* Device name must be "nmdm%s%c", where %c is 'A' or 'B'. */
 174         end = name + strlen(name) - 1;
 175         endc = *end;
 176         if (endc != 'A' && endc != 'B')
 177                 return;
 178
 179         ns = malloc(sizeof(*ns), M_NMDM, M_WAITOK | M_ZERO);
 180         mtx_init(&ns->ns_mtx, "nmdm", NULL, MTX_DEF);
 181
 182         /* Hook the pairs together. */
 183         ns->ns_part1.np_pair = ns;
 184         ns->ns_part1.np_other = &ns->ns_part2;
 185         TASK_INIT(&ns->ns_part1.np_task, 0, nmdm_task_tty, &ns->ns_part1);
 186         callout_init_mtx(&ns->ns_part1.np_callout, &ns->ns_mtx, 0);
 187
 188         ns->ns_part2.np_pair = ns;
 189         ns->ns_part2.np_other = &ns->ns_part1;
 190         TASK_INIT(&ns->ns_part2.np_task, 0, nmdm_task_tty, &ns->ns_part2);
 191         callout_init_mtx(&ns->ns_part2.np_callout, &ns->ns_mtx, 0);
 192
 193         /* Create device nodes. */
 194         tp = ns->ns_part1.np_tty = tty_alloc_mutex(&nmdm_class, &ns->ns_part1,
 195             &ns->ns_mtx);
 196         *end = 'A';
 197         error = tty_makedevf(tp, NULL, endc == 'A' ? TTYMK_CLONING : 0,
 198             "%s", name);
 199         if (error) {
 200                 *end = endc;
 201                 mtx_destroy(&ns->ns_mtx);
 202                 free(ns, M_NMDM);
 203                 return;
 204         }
 205
 206         tp = ns->ns_part2.np_tty = tty_alloc_mutex(&nmdm_class, &ns->ns_part2,
 207             &ns->ns_mtx);
 208         *end = 'B';
 209         error = tty_makedevf(tp, NULL, endc == 'B' ? TTYMK_CLONING : 0,
 210             "%s", name);
 211         if (error) {
 212                 *end = endc;
 213                 mtx_lock(&ns->ns_mtx);
 214                 /* see nmdm_free() */
 215                 ns->ns_part1.np_other = NULL;
 216                 atomic_add_int(&nmdm_count, 1);
 217                 tty_rel_gone(ns->ns_part1.np_tty);
 218                 return;
 219         }
 220
 221         if (endc == 'A')
 222                 *dev = ns->ns_part1.np_tty->t_dev;
 223         else
 224                 *dev = ns->ns_part2.np_tty->t_dev;
 225
 226         *end = endc;
 227         atomic_add_int(&nmdm_count, 1);
 228 }
 229
 230 static void
 231 nmdm_timeout(void *arg)
 232 {
 233         struct nmdmpart *np = arg;
 234
 235         if (np->np_rate == 0)
 236                 return;
 237
 238         /*
 239          * Do a simple Floyd-Steinberg dither here to avoid FP math.
 240          * Wipe out unused quota from last tick.
 241          */
 242         np->np_accumulator += np->np_credits;
 243         np->np_quota = np->np_accumulator >> QS;
 244         np->np_accumulator &= ((1 << QS) - 1);
 245
 246         taskqueue_enqueue(taskqueue_swi, &np->np_task);
 247         callout_reset(&np->np_callout, np->np_rate, nmdm_timeout, np);
 248 }
 249
 250 static void
 251 nmdm_task_tty(void *arg, int pending __unused)
 252 {
 253         struct tty *tp, *otp;
 254         struct nmdmpart *np = arg;
 255         char c;
 256
 257         tp = np->np_tty;
 258         tty_lock(tp);
 259         if (tty_gone(tp)) {
 260                 tty_unlock(tp);
 261                 return;
 262         }
 263
 264         otp = np->np_other->np_tty;
 265         KASSERT(otp != NULL, ("NULL otp in nmdmstart"));
 266         KASSERT(otp != tp, ("NULL otp == tp nmdmstart"));
 267         if (np->np_other->np_dcd) {
 268                 if (!tty_opened(tp)) {
 269                         np->np_other->np_dcd = 0;
 270                         ttydisc_modem(otp, 0);
 271                 }
 272         } else {
 273                 if (tty_opened(tp)) {
 274                         np->np_other->np_dcd = 1;
 275                         ttydisc_modem(otp, 1);
 276                 }
 277         }
 278
 279         /* This may happen when we are in detach process. */
 280         if (tty_gone(otp)) {
 281                 tty_unlock(otp);
 282                 return;
 283         }
 284
 285         while (ttydisc_rint_poll(otp) > 0) {
 286                 if (np->np_rate && !np->np_quota)
 287                         break;
 288                 if (ttydisc_getc(tp, &c, 1) != 1)
 289                         break;
 290                 np->np_quota--;
 291                 ttydisc_rint(otp, c, 0);
 292         }
 293
 294         ttydisc_rint_done(otp);
 295
 296         tty_unlock(tp);
 297 }
 298
 299 static int
 300 bits_per_char(struct termios *t)
 301 {
 302         int bits;
 303
 304         bits = 1;               /* start bit */
 305         switch (t->c_cflag & CSIZE) {
 306         case CS5:       bits += 5;      break;
 307         case CS6:       bits += 6;      break;
 308         case CS7:       bits += 7;      break;
 309         case CS8:       bits += 8;      break;
 310         }
 311         bits++;                 /* stop bit */
 312         if (t->c_cflag & PARENB)
 313                 bits++;
 314         if (t->c_cflag & CSTOPB)
 315                 bits++;
 316         return (bits);
 317 }
 318
 319 static int
 320 nmdm_param(struct tty *tp, struct termios *t)
 321 {
 322         struct nmdmpart *np = tty_softc(tp);
 323         struct tty *tp2;
 324         int bpc, rate, speed, i;
 325
 326         tp2 = np->np_other->np_tty;
 327
 328         if (!((t->c_cflag | tp2->t_termios.c_cflag) & CDSR_OFLOW)) {
 329                 np->np_rate = 0;
 330                 np->np_other->np_rate = 0;
 331                 return (0);
 332         }
 333
 334         /*
 335          * DSRFLOW one either side enables rate-simulation for both
 336          * directions.
 337          * NB: the two directions may run at different rates.
 338          */
 339
 340         /* Find the larger of the number of bits transmitted */
 341         bpc = imax(bits_per_char(t), bits_per_char(&tp2->t_termios));
 342
 343         for (i = 0; i < 2; i++) {
 344                 /* Use the slower of our receive and their transmit rate */
 345                 speed = imin(tp2->t_termios.c_ospeed, t->c_ispeed);
 346                 if (speed == 0) {
 347                         np->np_rate = 0;
 348                         np->np_other->np_rate = 0;
 349                         return (0);
 350                 }
 351
 352                 speed <<= QS;                   /* [bit/sec, scaled] */
 353                 speed /= bpc;                   /* [char/sec, scaled] */
 354                 rate = (hz << QS) / speed;      /* [hz per callout] */
 355                 if (rate == 0)
 356                         rate = 1;
 357
 358                 speed *= rate;
 359                 speed /= hz;                    /* [(char/sec)/tick, scaled */
 360
 361                 np->np_credits = speed;
 362                 np->np_rate = rate;
 363                 callout_reset(&np->np_callout, rate, nmdm_timeout, np);
 364
 365                 /*
 366                  * swap pointers for second pass so the other end gets
 367                  * updated as well.
 368                  */
 369                 np = np->np_other;
 370                 t = &tp2->t_termios;
 371                 tp2 = tp;
 372         }
 373
 374         return (0);
 375 }
 376
 377 static int
 378 nmdm_modem(struct tty *tp, int sigon, int sigoff)
 379 {
 380         struct nmdmpart *np = tty_softc(tp);
 381         int i = 0;
 382
 383         if (sigon || sigoff) {
 384                 if (sigon & SER_DTR)
 385                         np->np_other->np_dcd = 1;
 386                 if (sigoff & SER_DTR)
 387                         np->np_other->np_dcd = 0;
 388
 389                 ttydisc_modem(np->np_other->np_tty, np->np_other->np_dcd);
 390
 391                 return (0);
 392         } else {
 393                 if (np->np_dcd)
 394                         i |= SER_DCD;
 395                 if (np->np_other->np_dcd)
 396                         i |= SER_DTR;
 397
 398                 return (i);
 399         }
 400 }
 401
 402 static void
 403 nmdm_inwakeup(struct tty *tp)
 404 {
 405         struct nmdmpart *np = tty_softc(tp);
 406
 407         /* We can receive again, so wake up the other side. */
 408         taskqueue_enqueue(taskqueue_swi, &np->np_other->np_task);
 409 }
 410
 411 static void
 412 nmdm_outwakeup(struct tty *tp)
 413 {
 414         struct nmdmpart *np = tty_softc(tp);
 415
 416         /* We can transmit again, so wake up our side. */
 417         taskqueue_enqueue(taskqueue_swi, &np->np_task);
 418 }
 419
 420 /*
 421  * Module handling
 422  */
 423 static int
 424 nmdm_modevent(module_t mod, int type, void *data)
 425 {
 426         static eventhandler_tag tag;
 427
 428         switch(type) {
 429         case MOD_LOAD:
 430                 tag = EVENTHANDLER_REGISTER(dev_clone, nmdm_clone, 0, 1000);
 431                 if (tag == NULL)
 432                         return (ENOMEM);
 433                 break;
 434
 435         case MOD_SHUTDOWN:
 436                 break;
 437
 438         case MOD_UNLOAD:
 439                 if (nmdm_count != 0)
 440                         return (EBUSY);
 441                 EVENTHANDLER_DEREGISTER(dev_clone, tag);
 442                 break;
 443
 444         default:
 445                 return (EOPNOTSUPP);
 446         }
 447
 448         return (0);
 449 }
 450
 451 DEV_MODULE(nmdm, nmdm_modevent, NULL);