drivers/staging/speakup/spk_ttyio.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/types.h>
   3 #include <linux/tty.h>
   4 #include <linux/tty_flip.h>
   5 #include <linux/slab.h>
   6
   7 #include "speakup.h"
   8 #include "spk_types.h"
   9 #include "spk_priv.h"
  10
  11 struct spk_ldisc_data {
  12         char buf;
  13         struct semaphore sem;
  14         bool buf_free;
  15 };
  16
  17 static struct spk_synth *spk_ttyio_synth;
  18 static struct tty_struct *speakup_tty;
  19 /* mutex to protect against speakup_tty disappearing from underneath us while
  20  * we are using it. this can happen when the device physically unplugged,
  21  * while in use. it also serialises access to speakup_tty.
  22  */
  23 static DEFINE_MUTEX(speakup_tty_mutex);
  24
  25 static int ser_to_dev(int ser, dev_t *dev_no)
  26 {
  27         if (ser < 0 || ser > (255 - 64)) {
  28                 pr_err("speakup: Invalid ser param. Must be between 0 and 191 inclusive.\n");
  29                 return -EINVAL;
  30         }
  31
  32         *dev_no = MKDEV(4, (64 + ser));
  33         return 0;
  34 }
  35
  36 static int get_dev_to_use(struct spk_synth *synth, dev_t *dev_no)
  37 {
  38         /* use ser only when dev is not specified */
  39         if (strcmp(synth->dev_name, SYNTH_DEFAULT_DEV) ||
  40             synth->ser == SYNTH_DEFAULT_SER)
  41                 return tty_dev_name_to_number(synth->dev_name, dev_no);
  42
  43         return ser_to_dev(synth->ser, dev_no);
  44 }
  45
  46 static int spk_ttyio_ldisc_open(struct tty_struct *tty)
  47 {
  48         struct spk_ldisc_data *ldisc_data;
  49
  50         if (tty != speakup_tty)
  51                 /* Somebody tried to use this line discipline outside speakup */
  52                 return -ENODEV;
  53
  54         if (tty->ops->write == NULL)
  55                 return -EOPNOTSUPP;
  56
  57         ldisc_data = kmalloc(sizeof(struct spk_ldisc_data), GFP_KERNEL);
  58         if (!ldisc_data)
  59                 return -ENOMEM;
  60
  61         sema_init(&ldisc_data->sem, 0);
  62         ldisc_data->buf_free = true;
  63         tty->disc_data = ldisc_data;
  64
  65         return 0;
  66 }
  67
  68 static void spk_ttyio_ldisc_close(struct tty_struct *tty)
  69 {
  70         mutex_lock(&speakup_tty_mutex);
  71         kfree(speakup_tty->disc_data);
  72         speakup_tty = NULL;
  73         mutex_unlock(&speakup_tty_mutex);
  74 }
  75
  76 static int spk_ttyio_receive_buf2(struct tty_struct *tty,
  77                                   const unsigned char *cp, char *fp, int count)
  78 {
  79         struct spk_ldisc_data *ldisc_data = tty->disc_data;
  80
  81         if (spk_ttyio_synth->read_buff_add) {
  82                 int i;
  83
  84                 for (i = 0; i < count; i++)
  85                         spk_ttyio_synth->read_buff_add(cp[i]);
  86
  87                 return count;
  88         }
  89
  90         if (!ldisc_data->buf_free)
  91                 /* ttyio_in will tty_flip_buffer_push */
  92                 return 0;
  93
  94         /* Make sure the consumer has read buf before we have seen
  95          * buf_free == true and overwrite buf
  96          */
  97         mb();
  98
  99         ldisc_data->buf = cp[0];
 100         ldisc_data->buf_free = false;
 101         up(&ldisc_data->sem);
 102
 103         return 1;
 104 }
 105
 106 static struct tty_ldisc_ops spk_ttyio_ldisc_ops = {
 107         .owner          = THIS_MODULE,
 108         .magic          = TTY_LDISC_MAGIC,
 109         .name           = "speakup_ldisc",
 110         .open           = spk_ttyio_ldisc_open,
 111         .close          = spk_ttyio_ldisc_close,
 112         .receive_buf2   = spk_ttyio_receive_buf2,
 113 };
 114
 115 static int spk_ttyio_out(struct spk_synth *in_synth, const char ch);
 116 static int spk_ttyio_out_unicode(struct spk_synth *in_synth, u16 ch);
 117 static void spk_ttyio_send_xchar(char ch);
 118 static void spk_ttyio_tiocmset(unsigned int set, unsigned int clear);
 119 static unsigned char spk_ttyio_in(void);
 120 static unsigned char spk_ttyio_in_nowait(void);
 121 static void spk_ttyio_flush_buffer(void);
 122
 123 struct spk_io_ops spk_ttyio_ops = {
 124         .synth_out = spk_ttyio_out,
 125         .synth_out_unicode = spk_ttyio_out_unicode,
 126         .send_xchar = spk_ttyio_send_xchar,
 127         .tiocmset = spk_ttyio_tiocmset,
 128         .synth_in = spk_ttyio_in,
 129         .synth_in_nowait = spk_ttyio_in_nowait,
 130         .flush_buffer = spk_ttyio_flush_buffer,
 131 };
 132 EXPORT_SYMBOL_GPL(spk_ttyio_ops);
 133
 134 static inline void get_termios(struct tty_struct *tty, struct ktermios *out_termios)
 135 {
 136         down_read(&tty->termios_rwsem);
 137         *out_termios = tty->termios;
 138         up_read(&tty->termios_rwsem);
 139 }
 140
 141 static int spk_ttyio_initialise_ldisc(struct spk_synth *synth)
 142 {
 143         int ret = 0;
 144         struct tty_struct *tty;
 145         struct ktermios tmp_termios;
 146         dev_t dev;
 147
 148         ret = get_dev_to_use(synth, &dev);
 149         if (ret)
 150                 return ret;
 151
 152         tty = tty_kopen(dev);
 153         if (IS_ERR(tty))
 154                 return PTR_ERR(tty);
 155
 156         if (tty->ops->open)
 157                 ret = tty->ops->open(tty, NULL);
 158         else
 159                 ret = -ENODEV;
 160
 161         if (ret) {
 162                 tty_unlock(tty);
 163                 return ret;
 164         }
 165
 166         clear_bit(TTY_HUPPED, &tty->flags);
 167         /* ensure hardware flow control is enabled */
 168         get_termios(tty, &tmp_termios);
 169         if (!(tmp_termios.c_cflag & CRTSCTS)) {
 170                 tmp_termios.c_cflag |= CRTSCTS;
 171                 tty_set_termios(tty, &tmp_termios);
 172                 /*
 173                  * check c_cflag to see if it's updated as tty_set_termios may not return
 174                  * error even when no tty bits are changed by the request.
 175                  */
 176                 get_termios(tty, &tmp_termios);
 177                 if (!(tmp_termios.c_cflag & CRTSCTS))
 178                         pr_warn("speakup: Failed to set hardware flow control\n");
 179         }
 180
 181         tty_unlock(tty);
 182
 183         mutex_lock(&speakup_tty_mutex);
 184         speakup_tty = tty;
 185         ret = tty_set_ldisc(tty, N_SPEAKUP);
 186         if (ret)
 187                 speakup_tty = NULL;
 188         mutex_unlock(&speakup_tty_mutex);
 189
 190         if (!ret)
 191                 /* Success */
 192                 return 0;
 193
 194         pr_err("speakup: Failed to set N_SPEAKUP on tty\n");
 195
 196         tty_lock(tty);
 197         if (tty->ops->close)
 198                 tty->ops->close(tty, NULL);
 199         tty_unlock(tty);
 200
 201         tty_kclose(tty);
 202
 203         return ret;
 204 }
 205
 206 void spk_ttyio_register_ldisc(void)
 207 {
 208         if (tty_register_ldisc(N_SPEAKUP, &spk_ttyio_ldisc_ops))
 209                 pr_warn("speakup: Error registering line discipline. Most synths won't work.\n");
 210 }
 211
 212 void spk_ttyio_unregister_ldisc(void)
 213 {
 214         if (tty_unregister_ldisc(N_SPEAKUP))
 215                 pr_warn("speakup: Couldn't unregister ldisc\n");
 216 }
 217
 218 static int spk_ttyio_out(struct spk_synth *in_synth, const char ch)
 219 {
 220         mutex_lock(&speakup_tty_mutex);
 221         if (in_synth->alive && speakup_tty && speakup_tty->ops->write) {
 222                 int ret = speakup_tty->ops->write(speakup_tty, &ch, 1);
 223
 224                 mutex_unlock(&speakup_tty_mutex);
 225                 if (ret == 0)
 226                         /* No room */
 227                         return 0;
 228                 if (ret < 0) {
 229                         pr_warn("%s: I/O error, deactivating speakup\n", in_synth->long_name);
 230                         /* No synth any more, so nobody will restart TTYs, and we thus
 231                          * need to do it ourselves.  Now that there is no synth we can
 232                          * let application flood anyway
 233                          */
 234                         in_synth->alive = 0;
 235                         speakup_start_ttys();
 236                         return 0;
 237                 }
 238                 return 1;
 239         }
 240
 241         mutex_unlock(&speakup_tty_mutex);
 242         return 0;
 243 }
 244
 245 static int spk_ttyio_out_unicode(struct spk_synth *in_synth, u16 ch)
 246 {
 247         int ret;
 248
 249         if (ch < 0x80)
 250                 ret = spk_ttyio_out(in_synth, ch);
 251         else if (ch < 0x800) {
 252                 ret  = spk_ttyio_out(in_synth, 0xc0 | (ch >> 6));
 253                 ret &= spk_ttyio_out(in_synth, 0x80 | (ch & 0x3f));
 254         } else {
 255                 ret  = spk_ttyio_out(in_synth, 0xe0 | (ch >> 12));
 256                 ret &= spk_ttyio_out(in_synth, 0x80 | ((ch >> 6) & 0x3f));
 257                 ret &= spk_ttyio_out(in_synth, 0x80 | (ch & 0x3f));
 258         }
 259         return ret;
 260 }
 261
 262 static int check_tty(struct tty_struct *tty)
 263 {
 264         if (!tty) {
 265                 pr_warn("%s: I/O error, deactivating speakup\n",
 266                         spk_ttyio_synth->long_name);
 267                 /* No synth any more, so nobody will restart TTYs, and we thus
 268                  * need to do it ourselves.  Now that there is no synth we can
 269                  * let application flood anyway
 270                  */
 271                 spk_ttyio_synth->alive = 0;
 272                 speakup_start_ttys();
 273                 return 1;
 274         }
 275
 276         return 0;
 277 }
 278
 279 static void spk_ttyio_send_xchar(char ch)
 280 {
 281         mutex_lock(&speakup_tty_mutex);
 282         if (check_tty(speakup_tty)) {
 283                 mutex_unlock(&speakup_tty_mutex);
 284                 return;
 285         }
 286
 287         if (speakup_tty->ops->send_xchar)
 288                 speakup_tty->ops->send_xchar(speakup_tty, ch);
 289         mutex_unlock(&speakup_tty_mutex);
 290 }
 291
 292 static void spk_ttyio_tiocmset(unsigned int set, unsigned int clear)
 293 {
 294         mutex_lock(&speakup_tty_mutex);
 295         if (check_tty(speakup_tty)) {
 296                 mutex_unlock(&speakup_tty_mutex);
 297                 return;
 298         }
 299
 300         if (speakup_tty->ops->tiocmset)
 301                 speakup_tty->ops->tiocmset(speakup_tty, set, clear);
 302         mutex_unlock(&speakup_tty_mutex);
 303 }
 304
 305 static unsigned char ttyio_in(int timeout)
 306 {
 307         struct spk_ldisc_data *ldisc_data = speakup_tty->disc_data;
 308         char rv;
 309
 310         if (down_timeout(&ldisc_data->sem, usecs_to_jiffies(timeout)) == -ETIME) {
 311                 if (timeout)
 312                         pr_warn("spk_ttyio: timeout (%d)  while waiting for input\n",
 313                                 timeout);
 314                 return 0xff;
 315         }
 316
 317         rv = ldisc_data->buf;
 318         /* Make sure we have read buf before we set buf_free to let
 319          * the producer overwrite it
 320          */
 321         mb();
 322         ldisc_data->buf_free = true;
 323         /* Let TTY push more characters */
 324         tty_flip_buffer_push(speakup_tty->port);
 325
 326         return rv;
 327 }
 328
 329 static unsigned char spk_ttyio_in(void)
 330 {
 331         return ttyio_in(SPK_SYNTH_TIMEOUT);
 332 }
 333
 334 static unsigned char spk_ttyio_in_nowait(void)
 335 {
 336         u8 rv = ttyio_in(0);
 337
 338         return (rv == 0xff) ? 0 : rv;
 339 }
 340
 341 static void spk_ttyio_flush_buffer(void)
 342 {
 343         mutex_lock(&speakup_tty_mutex);
 344         if (check_tty(speakup_tty)) {
 345                 mutex_unlock(&speakup_tty_mutex);
 346                 return;
 347         }
 348
 349         if (speakup_tty->ops->flush_buffer)
 350                 speakup_tty->ops->flush_buffer(speakup_tty);
 351
 352         mutex_unlock(&speakup_tty_mutex);
 353 }
 354
 355 int spk_ttyio_synth_probe(struct spk_synth *synth)
 356 {
 357         int rv = spk_ttyio_initialise_ldisc(synth);
 358
 359         if (rv)
 360                 return rv;
 361
 362         synth->alive = 1;
 363         spk_ttyio_synth = synth;
 364
 365         return 0;
 366 }
 367 EXPORT_SYMBOL_GPL(spk_ttyio_synth_probe);
 368
 369 void spk_ttyio_release(void)
 370 {
 371         if (!speakup_tty)
 372                 return;
 373
 374         tty_lock(speakup_tty);
 375
 376         if (speakup_tty->ops->close)
 377                 speakup_tty->ops->close(speakup_tty, NULL);
 378
 379         tty_ldisc_flush(speakup_tty);
 380         tty_unlock(speakup_tty);
 381         tty_kclose(speakup_tty);
 382 }
 383 EXPORT_SYMBOL_GPL(spk_ttyio_release);
 384
 385 const char *spk_ttyio_synth_immediate(struct spk_synth *synth, const char *buff)
 386 {
 387         u_char ch;
 388
 389         while ((ch = *buff)) {
 390                 if (ch == '\n')
 391                         ch = synth->procspeech;
 392                 if (tty_write_room(speakup_tty) < 1 || !synth->io_ops->synth_out(synth, ch))
 393                         return buff;
 394                 buff++;
 395         }
 396         return NULL;
 397 }
 398 EXPORT_SYMBOL_GPL(spk_ttyio_synth_immediate);