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