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 size_t spk_ttyio_receive_buf2(struct tty_struct *tty, const u8 *cp,
75 				     const u8 *fp, size_t count)
76 {
77 	struct spk_ldisc_data *ldisc_data = tty->disc_data;
78 	struct spk_synth *synth = ldisc_data->synth;
79 
80 	if (synth->read_buff_add) {
81 		unsigned int i;
82 
83 		for (i = 0; i < count; i++)
84 			synth->read_buff_add(cp[i]);
85 
86 		return count;
87 	}
88 
89 	if (!ldisc_data->buf_free)
90 		/* ttyio_in will tty_flip_buffer_push */
91 		return 0;
92 
93 	/* Make sure the consumer has read buf before we have seen
94 	 * buf_free == true and overwrite buf
95 	 */
96 	mb();
97 
98 	ldisc_data->buf = cp[0];
99 	ldisc_data->buf_free = false;
100 	complete(&ldisc_data->completion);
101 
102 	return 1;
103 }
104 
105 static struct tty_ldisc_ops spk_ttyio_ldisc_ops = {
106 	.owner          = THIS_MODULE,
107 	.num		= N_SPEAKUP,
108 	.name           = "speakup_ldisc",
109 	.open           = spk_ttyio_ldisc_open,
110 	.close          = spk_ttyio_ldisc_close,
111 	.receive_buf2	= spk_ttyio_receive_buf2,
112 };
113 
114 static int spk_ttyio_out(struct spk_synth *in_synth, const char ch);
115 static int spk_ttyio_out_unicode(struct spk_synth *in_synth, u16 ch);
116 static void spk_ttyio_send_xchar(struct spk_synth *in_synth, char ch);
117 static void spk_ttyio_tiocmset(struct spk_synth *in_synth, unsigned int set, unsigned int clear);
118 static unsigned char spk_ttyio_in(struct spk_synth *in_synth);
119 static unsigned char spk_ttyio_in_nowait(struct spk_synth *in_synth);
120 static void spk_ttyio_flush_buffer(struct spk_synth *in_synth);
121 static int spk_ttyio_wait_for_xmitr(struct spk_synth *in_synth);
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 	.wait_for_xmitr = spk_ttyio_wait_for_xmitr,
132 };
133 EXPORT_SYMBOL_GPL(spk_ttyio_ops);
134 
135 static inline void get_termios(struct tty_struct *tty,
136 			       struct ktermios *out_termios)
137 {
138 	down_read(&tty->termios_rwsem);
139 	*out_termios = tty->termios;
140 	up_read(&tty->termios_rwsem);
141 }
142 
143 static int spk_ttyio_initialise_ldisc(struct spk_synth *synth)
144 {
145 	int ret = 0;
146 	struct tty_struct *tty;
147 	struct ktermios tmp_termios;
148 	dev_t dev;
149 
150 	ret = get_dev_to_use(synth, &dev);
151 	if (ret)
152 		return ret;
153 
154 	tty = tty_kopen_exclusive(dev);
155 	if (IS_ERR(tty))
156 		return PTR_ERR(tty);
157 
158 	if (tty->ops->open)
159 		ret = tty->ops->open(tty, NULL);
160 	else
161 		ret = -ENODEV;
162 
163 	if (ret) {
164 		tty_unlock(tty);
165 		return ret;
166 	}
167 
168 	clear_bit(TTY_HUPPED, &tty->flags);
169 	/* ensure hardware flow control is enabled */
170 	get_termios(tty, &tmp_termios);
171 	if (!(tmp_termios.c_cflag & CRTSCTS)) {
172 		tmp_termios.c_cflag |= CRTSCTS;
173 		tty_set_termios(tty, &tmp_termios);
174 		/*
175 		 * check c_cflag to see if it's updated as tty_set_termios
176 		 * may not return error even when no tty bits are
177 		 * changed by the request.
178 		 */
179 		get_termios(tty, &tmp_termios);
180 		if (!(tmp_termios.c_cflag & CRTSCTS))
181 			pr_warn("speakup: Failed to set hardware flow control\n");
182 	}
183 
184 	tty_unlock(tty);
185 
186 	mutex_lock(&speakup_tty_mutex);
187 	speakup_tty = tty;
188 	ret = tty_set_ldisc(tty, N_SPEAKUP);
189 	speakup_tty = NULL;
190 	mutex_unlock(&speakup_tty_mutex);
191 
192 	if (!ret) {
193 		/* Success */
194 		struct spk_ldisc_data *ldisc_data = tty->disc_data;
195 
196 		ldisc_data->synth = synth;
197 		synth->dev = tty;
198 		return 0;
199 	}
200 
201 	pr_err("speakup: Failed to set N_SPEAKUP on tty\n");
202 
203 	tty_lock(tty);
204 	if (tty->ops->close)
205 		tty->ops->close(tty, NULL);
206 	tty_unlock(tty);
207 
208 	tty_kclose(tty);
209 
210 	return ret;
211 }
212 
213 void spk_ttyio_register_ldisc(void)
214 {
215 	if (tty_register_ldisc(&spk_ttyio_ldisc_ops))
216 		pr_warn("speakup: Error registering line discipline. Most synths won't work.\n");
217 }
218 
219 void spk_ttyio_unregister_ldisc(void)
220 {
221 	tty_unregister_ldisc(&spk_ttyio_ldisc_ops);
222 }
223 
224 static int spk_ttyio_out(struct spk_synth *in_synth, const char ch)
225 {
226 	struct tty_struct *tty = in_synth->dev;
227 	int ret;
228 
229 	if (!in_synth->alive || !tty->ops->write)
230 		return 0;
231 
232 	ret = tty->ops->write(tty, &ch, 1);
233 
234 	if (ret == 0)
235 		/* No room */
236 		return 0;
237 
238 	if (ret > 0)
239 		/* Success */
240 		return 1;
241 
242 	pr_warn("%s: I/O error, deactivating speakup\n",
243 		in_synth->long_name);
244 	/* No synth any more, so nobody will restart TTYs,
245 	 * and we thus need to do it ourselves.  Now that there
246 	 * is no synth we can let application flood anyway
247 	 */
248 	in_synth->alive = 0;
249 	speakup_start_ttys();
250 	return 0;
251 }
252 
253 static int spk_ttyio_out_unicode(struct spk_synth *in_synth, u16 ch)
254 {
255 	int ret;
256 
257 	if (ch < 0x80) {
258 		ret = spk_ttyio_out(in_synth, ch);
259 	} else if (ch < 0x800) {
260 		ret  = spk_ttyio_out(in_synth, 0xc0 | (ch >> 6));
261 		ret &= spk_ttyio_out(in_synth, 0x80 | (ch & 0x3f));
262 	} else {
263 		ret  = spk_ttyio_out(in_synth, 0xe0 | (ch >> 12));
264 		ret &= spk_ttyio_out(in_synth, 0x80 | ((ch >> 6) & 0x3f));
265 		ret &= spk_ttyio_out(in_synth, 0x80 | (ch & 0x3f));
266 	}
267 	return ret;
268 }
269 
270 static void spk_ttyio_send_xchar(struct spk_synth *in_synth, char ch)
271 {
272 	struct tty_struct *tty = in_synth->dev;
273 
274 	if (tty->ops->send_xchar)
275 		tty->ops->send_xchar(tty, ch);
276 }
277 
278 static void spk_ttyio_tiocmset(struct spk_synth *in_synth, unsigned int set, unsigned int clear)
279 {
280 	struct tty_struct *tty = in_synth->dev;
281 
282 	if (tty->ops->tiocmset)
283 		tty->ops->tiocmset(tty, set, clear);
284 }
285 
286 static int spk_ttyio_wait_for_xmitr(struct spk_synth *in_synth)
287 {
288 	return 1;
289 }
290 
291 static unsigned char ttyio_in(struct spk_synth *in_synth, int timeout)
292 {
293 	struct tty_struct *tty = in_synth->dev;
294 	struct spk_ldisc_data *ldisc_data = tty->disc_data;
295 	char rv;
296 
297 	if (!timeout) {
298 		if (!try_wait_for_completion(&ldisc_data->completion))
299 			return 0xff;
300 	} else if (wait_for_completion_timeout(&ldisc_data->completion,
301 					usecs_to_jiffies(timeout)) == 0) {
302 		pr_warn("spk_ttyio: timeout (%d)  while waiting for input\n",
303 			timeout);
304 		return 0xff;
305 	}
306 
307 	rv = ldisc_data->buf;
308 	/* Make sure we have read buf before we set buf_free to let
309 	 * the producer overwrite it
310 	 */
311 	mb();
312 	ldisc_data->buf_free = true;
313 	/* Let TTY push more characters */
314 	tty_flip_buffer_push(tty->port);
315 
316 	return rv;
317 }
318 
319 static unsigned char spk_ttyio_in(struct spk_synth *in_synth)
320 {
321 	return ttyio_in(in_synth, SPK_SYNTH_TIMEOUT);
322 }
323 
324 static unsigned char spk_ttyio_in_nowait(struct spk_synth *in_synth)
325 {
326 	u8 rv = ttyio_in(in_synth, 0);
327 
328 	return (rv == 0xff) ? 0 : rv;
329 }
330 
331 static void spk_ttyio_flush_buffer(struct spk_synth *in_synth)
332 {
333 	struct tty_struct *tty = in_synth->dev;
334 
335 	if (tty->ops->flush_buffer)
336 		tty->ops->flush_buffer(tty);
337 }
338 
339 int spk_ttyio_synth_probe(struct spk_synth *synth)
340 {
341 	int rv = spk_ttyio_initialise_ldisc(synth);
342 
343 	if (rv)
344 		return rv;
345 
346 	synth->alive = 1;
347 
348 	return 0;
349 }
350 EXPORT_SYMBOL_GPL(spk_ttyio_synth_probe);
351 
352 void spk_ttyio_release(struct spk_synth *in_synth)
353 {
354 	struct tty_struct *tty = in_synth->dev;
355 
356 	if (tty == NULL)
357 		return;
358 
359 	tty_lock(tty);
360 
361 	if (tty->ops->close)
362 		tty->ops->close(tty, NULL);
363 
364 	tty_ldisc_flush(tty);
365 	tty_unlock(tty);
366 	tty_kclose(tty);
367 
368 	in_synth->dev = NULL;
369 }
370 EXPORT_SYMBOL_GPL(spk_ttyio_release);
371 
372 const char *spk_ttyio_synth_immediate(struct spk_synth *in_synth, const char *buff)
373 {
374 	struct tty_struct *tty = in_synth->dev;
375 	u_char ch;
376 
377 	while ((ch = *buff)) {
378 		if (ch == '\n')
379 			ch = in_synth->procspeech;
380 		if (tty_write_room(tty) < 1 ||
381 		    !in_synth->io_ops->synth_out(in_synth, ch))
382 			return buff;
383 		buff++;
384 	}
385 	return NULL;
386 }
387 EXPORT_SYMBOL_GPL(spk_ttyio_synth_immediate);
388