drivers/accessibility/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 completion completion;
  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->ops->write)
  51                 return -EOPNOTSUPP;
  52         speakup_tty = tty;
  53
  54         ldisc_data = kmalloc(sizeof(*ldisc_data), GFP_KERNEL);
  55         if (!ldisc_data)
  56                 return -ENOMEM;
  57
  58         init_completion(&ldisc_data->completion);
  59         ldisc_data->buf_free = true;
  60         speakup_tty->disc_data = ldisc_data;
  61
  62         return 0;
  63 }
  64
  65 static void spk_ttyio_ldisc_close(struct tty_struct *tty)
  66 {
  67         mutex_lock(&speakup_tty_mutex);
  68         kfree(speakup_tty->disc_data);
  69         speakup_tty = NULL;
  70         mutex_unlock(&speakup_tty_mutex);
  71 }
  72
  73 static int spk_ttyio_receive_buf2(struct tty_struct *tty,
  74                                   const unsigned char *cp, char *fp, int count)
  75 {
  76         struct spk_ldisc_data *ldisc_data = tty->disc_data;
  77
  78         if (spk_ttyio_synth->read_buff_add) {
  79                 int i;
  80
  81                 for (i = 0; i < count; i++)
  82                         spk_ttyio_synth->read_buff_add(cp[i]);
  83
  84                 return count;
  85         }
  86
  87         if (!ldisc_data->buf_free)
  88                 /* ttyio_in will tty_schedule_flip */
  89                 return 0;
  90
  91         /* Make sure the consumer has read buf before we have seen
  92          * buf_free == true and overwrite buf
  93          */
  94         mb();
  95
  96         ldisc_data->buf = cp[0];
  97         ldisc_data->buf_free = false;
  98         complete(&ldisc_data->completion);
  99
 100         return 1;
 101 }
 102
 103 static struct tty_ldisc_ops spk_ttyio_ldisc_ops = {
 104         .owner          = THIS_MODULE,
 105         .magic          = TTY_LDISC_MAGIC,
 106         .name           = "speakup_ldisc",
 107         .open           = spk_ttyio_ldisc_open,
 108         .close          = spk_ttyio_ldisc_close,
 109         .receive_buf2   = spk_ttyio_receive_buf2,
 110 };
 111
 112 static int spk_ttyio_out(struct spk_synth *in_synth, const char ch);
 113 static int spk_ttyio_out_unicode(struct spk_synth *in_synth, u16 ch);
 114 static void spk_ttyio_send_xchar(char ch);
 115 static void spk_ttyio_tiocmset(unsigned int set, unsigned int clear);
 116 static unsigned char spk_ttyio_in(void);
 117 static unsigned char spk_ttyio_in_nowait(void);
 118 static void spk_ttyio_flush_buffer(void);
 119 static int spk_ttyio_wait_for_xmitr(struct spk_synth *in_synth);
 120
 121 struct spk_io_ops spk_ttyio_ops = {
 122         .synth_out = spk_ttyio_out,
 123         .synth_out_unicode = spk_ttyio_out_unicode,
 124         .send_xchar = spk_ttyio_send_xchar,
 125         .tiocmset = spk_ttyio_tiocmset,
 126         .synth_in = spk_ttyio_in,
 127         .synth_in_nowait = spk_ttyio_in_nowait,
 128         .flush_buffer = spk_ttyio_flush_buffer,
 129         .wait_for_xmitr = spk_ttyio_wait_for_xmitr,
 130 };
 131 EXPORT_SYMBOL_GPL(spk_ttyio_ops);
 132
 133 static inline void get_termios(struct tty_struct *tty,
 134                                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
 174                  * may not return error even when no tty bits are
 175                  * changed by the request.
 176                  */
 177                 get_termios(tty, &tmp_termios);
 178                 if (!(tmp_termios.c_cflag & CRTSCTS))
 179                         pr_warn("speakup: Failed to set hardware flow control\n");
 180         }
 181
 182         tty_unlock(tty);
 183
 184         ret = tty_set_ldisc(tty, N_SPEAKUP);
 185         if (ret)
 186                 pr_err("speakup: Failed to set N_SPEAKUP on tty\n");
 187
 188         return ret;
 189 }
 190
 191 void spk_ttyio_register_ldisc(void)
 192 {
 193         if (tty_register_ldisc(N_SPEAKUP, &spk_ttyio_ldisc_ops))
 194                 pr_warn("speakup: Error registering line discipline. Most synths won't work.\n");
 195 }
 196
 197 void spk_ttyio_unregister_ldisc(void)
 198 {
 199         if (tty_unregister_ldisc(N_SPEAKUP))
 200                 pr_warn("speakup: Couldn't unregister ldisc\n");
 201 }
 202
 203 static int spk_ttyio_out(struct spk_synth *in_synth, const char ch)
 204 {
 205         mutex_lock(&speakup_tty_mutex);
 206         if (in_synth->alive && speakup_tty && speakup_tty->ops->write) {
 207                 int ret = speakup_tty->ops->write(speakup_tty, &ch, 1);
 208
 209                 mutex_unlock(&speakup_tty_mutex);
 210                 if (ret == 0)
 211                         /* No room */
 212                         return 0;
 213                 if (ret < 0) {
 214                         pr_warn("%s: I/O error, deactivating speakup\n",
 215                                 in_synth->long_name);
 216                         /* No synth any more, so nobody will restart TTYs,
 217                          * and we thus need to do it ourselves.  Now that there
 218                          * is no synth we can let application flood anyway
 219                          */
 220                         in_synth->alive = 0;
 221                         speakup_start_ttys();
 222                         return 0;
 223                 }
 224                 return 1;
 225         }
 226
 227         mutex_unlock(&speakup_tty_mutex);
 228         return 0;
 229 }
 230
 231 static int spk_ttyio_out_unicode(struct spk_synth *in_synth, u16 ch)
 232 {
 233         int ret;
 234
 235         if (ch < 0x80) {
 236                 ret = spk_ttyio_out(in_synth, ch);
 237         } else if (ch < 0x800) {
 238                 ret  = spk_ttyio_out(in_synth, 0xc0 | (ch >> 6));
 239                 ret &= spk_ttyio_out(in_synth, 0x80 | (ch & 0x3f));
 240         } else {
 241                 ret  = spk_ttyio_out(in_synth, 0xe0 | (ch >> 12));
 242                 ret &= spk_ttyio_out(in_synth, 0x80 | ((ch >> 6) & 0x3f));
 243                 ret &= spk_ttyio_out(in_synth, 0x80 | (ch & 0x3f));
 244         }
 245         return ret;
 246 }
 247
 248 static int check_tty(struct tty_struct *tty)
 249 {
 250         if (!tty) {
 251                 pr_warn("%s: I/O error, deactivating speakup\n",
 252                         spk_ttyio_synth->long_name);
 253                 /* No synth any more, so nobody will restart TTYs, and we thus
 254                  * need to do it ourselves.  Now that there is no synth we can
 255                  * let application flood anyway
 256                  */
 257                 spk_ttyio_synth->alive = 0;
 258                 speakup_start_ttys();
 259                 return 1;
 260         }
 261
 262         return 0;
 263 }
 264
 265 static void spk_ttyio_send_xchar(char ch)
 266 {
 267         mutex_lock(&speakup_tty_mutex);
 268         if (check_tty(speakup_tty)) {
 269                 mutex_unlock(&speakup_tty_mutex);
 270                 return;
 271         }
 272
 273         if (speakup_tty->ops->send_xchar)
 274                 speakup_tty->ops->send_xchar(speakup_tty, ch);
 275         mutex_unlock(&speakup_tty_mutex);
 276 }
 277
 278 static void spk_ttyio_tiocmset(unsigned int set, unsigned int clear)
 279 {
 280         mutex_lock(&speakup_tty_mutex);
 281         if (check_tty(speakup_tty)) {
 282                 mutex_unlock(&speakup_tty_mutex);
 283                 return;
 284         }
 285
 286         if (speakup_tty->ops->tiocmset)
 287                 speakup_tty->ops->tiocmset(speakup_tty, set, clear);
 288         mutex_unlock(&speakup_tty_mutex);
 289 }
 290
 291 static int spk_ttyio_wait_for_xmitr(struct spk_synth *in_synth)
 292 {
 293         return 1;
 294 }
 295
 296 static unsigned char ttyio_in(int timeout)
 297 {
 298         struct spk_ldisc_data *ldisc_data = speakup_tty->disc_data;
 299         char rv;
 300
 301         if (wait_for_completion_timeout(&ldisc_data->completion,
 302                                         usecs_to_jiffies(timeout)) == 0) {
 303                 if (timeout)
 304                         pr_warn("spk_ttyio: timeout (%d)  while waiting for input\n",
 305                                 timeout);
 306                 return 0xff;
 307         }
 308
 309         rv = ldisc_data->buf;
 310         /* Make sure we have read buf before we set buf_free to let
 311          * the producer overwrite it
 312          */
 313         mb();
 314         ldisc_data->buf_free = true;
 315         /* Let TTY push more characters */
 316         tty_schedule_flip(speakup_tty->port);
 317
 318         return rv;
 319 }
 320
 321 static unsigned char spk_ttyio_in(void)
 322 {
 323         return ttyio_in(SPK_SYNTH_TIMEOUT);
 324 }
 325
 326 static unsigned char spk_ttyio_in_nowait(void)
 327 {
 328         u8 rv = ttyio_in(0);
 329
 330         return (rv == 0xff) ? 0 : rv;
 331 }
 332
 333 static void spk_ttyio_flush_buffer(void)
 334 {
 335         mutex_lock(&speakup_tty_mutex);
 336         if (check_tty(speakup_tty)) {
 337                 mutex_unlock(&speakup_tty_mutex);
 338                 return;
 339         }
 340
 341         if (speakup_tty->ops->flush_buffer)
 342                 speakup_tty->ops->flush_buffer(speakup_tty);
 343
 344         mutex_unlock(&speakup_tty_mutex);
 345 }
 346
 347 int spk_ttyio_synth_probe(struct spk_synth *synth)
 348 {
 349         int rv = spk_ttyio_initialise_ldisc(synth);
 350
 351         if (rv)
 352                 return rv;
 353
 354         synth->alive = 1;
 355         spk_ttyio_synth = synth;
 356
 357         return 0;
 358 }
 359 EXPORT_SYMBOL_GPL(spk_ttyio_synth_probe);
 360
 361 void spk_ttyio_release(void)
 362 {
 363         if (!speakup_tty)
 364                 return;
 365
 366         tty_lock(speakup_tty);
 367
 368         if (speakup_tty->ops->close)
 369                 speakup_tty->ops->close(speakup_tty, NULL);
 370
 371         tty_ldisc_flush(speakup_tty);
 372         tty_unlock(speakup_tty);
 373         tty_kclose(speakup_tty);
 374 }
 375 EXPORT_SYMBOL_GPL(spk_ttyio_release);
 376
 377 const char *spk_ttyio_synth_immediate(struct spk_synth *synth, const char *buff)
 378 {
 379         u_char ch;
 380
 381         while ((ch = *buff)) {
 382                 if (ch == '\n')
 383                         ch = synth->procspeech;
 384                 if (tty_write_room(speakup_tty) < 1 ||
 385                     !synth->io_ops->synth_out(synth, ch))
 386                         return buff;
 387                 buff++;
 388         }
 389         return NULL;
 390 }
 391 EXPORT_SYMBOL_GPL(spk_ttyio_synth_immediate);