xref: /freebsd/sys/kern/subr_terminal.c (revision 43a5ec4eb41567cc92586503212743d89686d78f) 
1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3  *
4  * Copyright (c) 2009 The FreeBSD Foundation
5  *
6  * This software was developed by Ed Schouten under sponsorship from the
7  * FreeBSD Foundation.
8  *
9  * Redistribution and use in source and binary forms, with or without
10  * modification, are permitted provided that the following conditions
11  * are met:
12  * 1. Redistributions of source code must retain the above copyright
13  *    notice, this list of conditions and the following disclaimer.
14  * 2. Redistributions in binary form must reproduce the above copyright
15  *    notice, this list of conditions and the following disclaimer in the
16  *    documentation and/or other materials provided with the distribution.
17  *
18  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
19  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
22  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28  * SUCH DAMAGE.
29  */
30 
31 #include <sys/cdefs.h>
32 __FBSDID("$FreeBSD$");
33 
34 #include <sys/param.h>
35 #include <sys/cons.h>
36 #include <sys/consio.h>
37 #include <sys/kernel.h>
38 #include <sys/lock.h>
39 #include <sys/malloc.h>
40 #include <sys/mutex.h>
41 #include <sys/systm.h>
42 #include <sys/terminal.h>
43 #include <sys/tty.h>
44 
45 #include <machine/stdarg.h>
46 
47 static MALLOC_DEFINE(M_TERMINAL, "terminal", "terminal device");
48 
49 /*
50  * Locking.
51  *
52  * Normally we don't need to lock down the terminal emulator, because
53  * the TTY lock is already held when calling teken_input().
54  * Unfortunately this is not the case when the terminal acts as a
55  * console device, because cnputc() can be called at the same time.
56  * This means terminals may need to be locked down using a spin lock.
57  */
58 #define	TERMINAL_LOCK(tm)	do {					\
59 	if ((tm)->tm_flags & TF_CONS)					\
60 		mtx_lock_spin(&(tm)->tm_mtx);				\
61 	else if ((tm)->tm_tty != NULL)					\
62 		tty_lock((tm)->tm_tty);					\
63 } while (0)
64 #define	TERMINAL_UNLOCK(tm)	do {					\
65 	if ((tm)->tm_flags & TF_CONS)					\
66 		mtx_unlock_spin(&(tm)->tm_mtx);				\
67 	else if ((tm)->tm_tty != NULL)					\
68 		tty_unlock((tm)->tm_tty);				\
69 } while (0)
70 #define	TERMINAL_LOCK_TTY(tm)	do {					\
71 	if ((tm)->tm_flags & TF_CONS)					\
72 		mtx_lock_spin(&(tm)->tm_mtx);				\
73 } while (0)
74 #define	TERMINAL_UNLOCK_TTY(tm)	do {					\
75 	if ((tm)->tm_flags & TF_CONS)					\
76 		mtx_unlock_spin(&(tm)->tm_mtx);				\
77 } while (0)
78 #define	TERMINAL_LOCK_CONS(tm)		mtx_lock_spin(&(tm)->tm_mtx)
79 #define	TERMINAL_UNLOCK_CONS(tm)	mtx_unlock_spin(&(tm)->tm_mtx)
80 
81 /*
82  * TTY routines.
83  */
84 
85 static tsw_open_t	termtty_open;
86 static tsw_close_t	termtty_close;
87 static tsw_outwakeup_t	termtty_outwakeup;
88 static tsw_ioctl_t	termtty_ioctl;
89 static tsw_mmap_t	termtty_mmap;
90 
91 static struct ttydevsw terminal_tty_class = {
92 	.tsw_open	= termtty_open,
93 	.tsw_close	= termtty_close,
94 	.tsw_outwakeup	= termtty_outwakeup,
95 	.tsw_ioctl	= termtty_ioctl,
96 	.tsw_mmap	= termtty_mmap,
97 };
98 
99 /*
100  * Terminal emulator routines.
101  */
102 
103 static tf_bell_t	termteken_bell;
104 static tf_cursor_t	termteken_cursor;
105 static tf_putchar_t	termteken_putchar;
106 static tf_fill_t	termteken_fill;
107 static tf_copy_t	termteken_copy;
108 static tf_pre_input_t	termteken_pre_input;
109 static tf_post_input_t	termteken_post_input;
110 static tf_param_t	termteken_param;
111 static tf_respond_t	termteken_respond;
112 
113 static teken_funcs_t terminal_drawmethods = {
114 	.tf_bell	= termteken_bell,
115 	.tf_cursor	= termteken_cursor,
116 	.tf_putchar	= termteken_putchar,
117 	.tf_fill	= termteken_fill,
118 	.tf_copy	= termteken_copy,
119 	.tf_pre_input	= termteken_pre_input,
120 	.tf_post_input	= termteken_post_input,
121 	.tf_param	= termteken_param,
122 	.tf_respond	= termteken_respond,
123 };
124 
125 /* Kernel message formatting. */
126 static teken_attr_t kernel_message = {
127 	.ta_fgcolor	= TCHAR_FGCOLOR(TERMINAL_KERN_ATTR),
128 	.ta_bgcolor	= TCHAR_BGCOLOR(TERMINAL_KERN_ATTR),
129 	.ta_format	= TCHAR_FORMAT(TERMINAL_KERN_ATTR)
130 };
131 
132 static teken_attr_t default_message = {
133 	.ta_fgcolor	= TCHAR_FGCOLOR(TERMINAL_NORM_ATTR),
134 	.ta_bgcolor	= TCHAR_BGCOLOR(TERMINAL_NORM_ATTR),
135 	.ta_format	= TCHAR_FORMAT(TERMINAL_NORM_ATTR)
136 };
137 
138 /* Fudge fg brightness as TF_BOLD (shifted). */
139 #define	TCOLOR_FG_FUDGED(color) __extension__ ({			\
140 	teken_color_t _c;						\
141 									\
142 	_c = (color);							\
143 	TCOLOR_FG(_c & 7) | ((_c & 8) << 18);				\
144 })
145 
146 /* Fudge bg brightness as TF_BLINK (shifted). */
147 #define	TCOLOR_BG_FUDGED(color) __extension__ ({			\
148 	teken_color_t _c;						\
149 									\
150 	_c = (color);							\
151 	TCOLOR_BG(_c & 7) | ((_c & 8) << 20);				\
152 })
153 
154 #define	TCOLOR_256TO16(color) __extension__ ({				\
155 	teken_color_t _c;						\
156 									\
157 	_c = (color);							\
158 	if (_c >= 16)							\
159 		_c = teken_256to16(_c);					\
160 	_c;								\
161 })
162 
163 #define	TCHAR_CREATE(c, a)	((c) | TFORMAT((a)->ta_format) |	\
164 	TCOLOR_FG_FUDGED(TCOLOR_256TO16((a)->ta_fgcolor)) |		\
165 	TCOLOR_BG_FUDGED(TCOLOR_256TO16((a)->ta_bgcolor)))
166 
167 static void
168 terminal_init(struct terminal *tm)
169 {
170 	int fg, bg;
171 
172 	if (tm->tm_flags & TF_CONS)
173 		mtx_init(&tm->tm_mtx, "trmlck", NULL, MTX_SPIN);
174 
175 	teken_init(&tm->tm_emulator, &terminal_drawmethods, tm);
176 
177 	fg = bg = -1;
178 	TUNABLE_INT_FETCH("teken.fg_color", &fg);
179 	TUNABLE_INT_FETCH("teken.bg_color", &bg);
180 
181 	if (fg != -1) {
182 		default_message.ta_fgcolor = fg;
183 		kernel_message.ta_fgcolor = fg;
184 	}
185 	if (bg != -1) {
186 		default_message.ta_bgcolor = bg;
187 		kernel_message.ta_bgcolor = bg;
188 	}
189 
190 	if (default_message.ta_bgcolor == TC_WHITE) {
191 		default_message.ta_bgcolor |= TC_LIGHT;
192 		kernel_message.ta_bgcolor |= TC_LIGHT;
193 	}
194 
195 	if (default_message.ta_bgcolor == TC_BLACK &&
196 	    default_message.ta_fgcolor < TC_NCOLORS)
197 		kernel_message.ta_fgcolor |= TC_LIGHT;
198 	teken_set_defattr(&tm->tm_emulator, &default_message);
199 }
200 
201 struct terminal *
202 terminal_alloc(const struct terminal_class *tc, void *softc)
203 {
204 	struct terminal *tm;
205 
206 	tm = malloc(sizeof(struct terminal), M_TERMINAL, M_WAITOK|M_ZERO);
207 	terminal_init(tm);
208 
209 	tm->tm_class = tc;
210 	tm->tm_softc = softc;
211 
212 	return (tm);
213 }
214 
215 static void
216 terminal_sync_ttysize(struct terminal *tm)
217 {
218 	struct tty *tp;
219 
220 	tp = tm->tm_tty;
221 	if (tp == NULL)
222 		return;
223 
224 	tty_lock(tp);
225 	tty_set_winsize(tp, &tm->tm_winsize);
226 	tty_unlock(tp);
227 }
228 
229 void
230 terminal_maketty(struct terminal *tm, const char *fmt, ...)
231 {
232 	struct tty *tp;
233 	char name[8];
234 	va_list ap;
235 
236 	va_start(ap, fmt);
237 	vsnrprintf(name, sizeof name, 32, fmt, ap);
238 	va_end(ap);
239 
240 	tp = tty_alloc(&terminal_tty_class, tm);
241 	tty_makedev(tp, NULL, "%s", name);
242 	tm->tm_tty = tp;
243 	terminal_sync_ttysize(tm);
244 }
245 
246 void
247 terminal_set_cursor(struct terminal *tm, const term_pos_t *pos)
248 {
249 
250 	teken_set_cursor(&tm->tm_emulator, pos);
251 }
252 
253 void
254 terminal_set_winsize_blank(struct terminal *tm, const struct winsize *size,
255     int blank, const term_attr_t *attr)
256 {
257 	term_rect_t r;
258 
259 	tm->tm_winsize = *size;
260 
261 	r.tr_begin.tp_row = r.tr_begin.tp_col = 0;
262 	r.tr_end.tp_row = size->ws_row;
263 	r.tr_end.tp_col = size->ws_col;
264 
265 	TERMINAL_LOCK(tm);
266 	if (blank == 0)
267 		teken_set_winsize_noreset(&tm->tm_emulator, &r.tr_end);
268 	else
269 		teken_set_winsize(&tm->tm_emulator, &r.tr_end);
270 	TERMINAL_UNLOCK(tm);
271 
272 	if ((blank != 0) && !(tm->tm_flags & TF_MUTE))
273 		tm->tm_class->tc_fill(tm, &r,
274 		    TCHAR_CREATE((teken_char_t)' ', attr));
275 
276 	terminal_sync_ttysize(tm);
277 }
278 
279 void
280 terminal_set_winsize(struct terminal *tm, const struct winsize *size)
281 {
282 
283 	terminal_set_winsize_blank(tm, size, 1,
284 	    (const term_attr_t *)&default_message);
285 }
286 
287 /*
288  * XXX: This function is a kludge.  Drivers like vt(4) need to
289  * temporarily stop input when resizing, etc.  This should ideally be
290  * handled within the driver.
291  */
292 
293 void
294 terminal_mute(struct terminal *tm, int yes)
295 {
296 
297 	TERMINAL_LOCK(tm);
298 	if (yes)
299 		tm->tm_flags |= TF_MUTE;
300 	else
301 		tm->tm_flags &= ~TF_MUTE;
302 	TERMINAL_UNLOCK(tm);
303 }
304 
305 void
306 terminal_input_char(struct terminal *tm, term_char_t c)
307 {
308 	struct tty *tp;
309 
310 	tp = tm->tm_tty;
311 	if (tp == NULL)
312 		return;
313 
314 	/*
315 	 * Strip off any attributes. Also ignore input of second part of
316 	 * CJK fullwidth characters, as we don't want to return these
317 	 * characters twice.
318 	 */
319 	if (TCHAR_FORMAT(c) & TF_CJK_RIGHT)
320 		return;
321 	c = TCHAR_CHARACTER(c);
322 
323 	tty_lock(tp);
324 	/*
325 	 * Conversion to UTF-8.
326 	 */
327 	if (c < 0x80) {
328 		ttydisc_rint(tp, c, 0);
329 	} else if (c < 0x800) {
330 		char str[2] = {
331 			0xc0 | (c >> 6),
332 			0x80 | (c & 0x3f)
333 		};
334 
335 		ttydisc_rint_simple(tp, str, sizeof str);
336 	} else if (c < 0x10000) {
337 		char str[3] = {
338 			0xe0 | (c >> 12),
339 			0x80 | ((c >> 6) & 0x3f),
340 			0x80 | (c & 0x3f)
341 		};
342 
343 		ttydisc_rint_simple(tp, str, sizeof str);
344 	} else {
345 		char str[4] = {
346 			0xf0 | (c >> 18),
347 			0x80 | ((c >> 12) & 0x3f),
348 			0x80 | ((c >> 6) & 0x3f),
349 			0x80 | (c & 0x3f)
350 		};
351 
352 		ttydisc_rint_simple(tp, str, sizeof str);
353 	}
354 	ttydisc_rint_done(tp);
355 	tty_unlock(tp);
356 }
357 
358 void
359 terminal_input_raw(struct terminal *tm, char c)
360 {
361 	struct tty *tp;
362 
363 	tp = tm->tm_tty;
364 	if (tp == NULL)
365 		return;
366 
367 	tty_lock(tp);
368 	ttydisc_rint(tp, c, 0);
369 	ttydisc_rint_done(tp);
370 	tty_unlock(tp);
371 }
372 
373 void
374 terminal_input_special(struct terminal *tm, unsigned int k)
375 {
376 	struct tty *tp;
377 	const char *str;
378 
379 	tp = tm->tm_tty;
380 	if (tp == NULL)
381 		return;
382 
383 	str = teken_get_sequence(&tm->tm_emulator, k);
384 	if (str == NULL)
385 		return;
386 
387 	tty_lock(tp);
388 	ttydisc_rint_simple(tp, str, strlen(str));
389 	ttydisc_rint_done(tp);
390 	tty_unlock(tp);
391 }
392 
393 /*
394  * Binding with the TTY layer.
395  */
396 
397 static int
398 termtty_open(struct tty *tp)
399 {
400 	struct terminal *tm = tty_softc(tp);
401 
402 	tm->tm_class->tc_opened(tm, 1);
403 	return (0);
404 }
405 
406 static void
407 termtty_close(struct tty *tp)
408 {
409 	struct terminal *tm = tty_softc(tp);
410 
411 	tm->tm_class->tc_opened(tm, 0);
412 }
413 
414 static void
415 termtty_outwakeup(struct tty *tp)
416 {
417 	struct terminal *tm = tty_softc(tp);
418 	char obuf[128];
419 	size_t olen;
420 	unsigned int flags = 0;
421 
422 	while ((olen = ttydisc_getc(tp, obuf, sizeof obuf)) > 0) {
423 		TERMINAL_LOCK_TTY(tm);
424 		if (!(tm->tm_flags & TF_MUTE)) {
425 			tm->tm_flags &= ~TF_BELL;
426 			teken_input(&tm->tm_emulator, obuf, olen);
427 			flags |= tm->tm_flags;
428 		}
429 		TERMINAL_UNLOCK_TTY(tm);
430 	}
431 
432 	TERMINAL_LOCK_TTY(tm);
433 	if (!(tm->tm_flags & TF_MUTE))
434 		tm->tm_class->tc_done(tm);
435 	TERMINAL_UNLOCK_TTY(tm);
436 	if (flags & TF_BELL)
437 		tm->tm_class->tc_bell(tm);
438 }
439 
440 static int
441 termtty_ioctl(struct tty *tp, u_long cmd, caddr_t data, struct thread *td)
442 {
443 	struct terminal *tm = tty_softc(tp);
444 	int error;
445 
446 	switch (cmd) {
447 	case CONS_GETINFO: {
448 		vid_info_t *vi = (vid_info_t *)data;
449 		const teken_pos_t *p;
450 		int fg, bg;
451 
452 		if (vi->size != sizeof(vid_info_t))
453 			return (EINVAL);
454 
455 		/* Already help the console driver by filling in some data. */
456 		p = teken_get_cursor(&tm->tm_emulator);
457 		vi->mv_row = p->tp_row;
458 		vi->mv_col = p->tp_col;
459 
460 		p = teken_get_winsize(&tm->tm_emulator);
461 		vi->mv_rsz = p->tp_row;
462 		vi->mv_csz = p->tp_col;
463 
464 		teken_get_defattr_cons25(&tm->tm_emulator, &fg, &bg);
465 		vi->mv_norm.fore = fg;
466 		vi->mv_norm.back = bg;
467 		/* XXX: keep vidcontrol happy; bold backgrounds. */
468 		vi->mv_rev.fore = bg;
469 		vi->mv_rev.back = fg & 0x7;
470 		break;
471 	}
472 	}
473 
474 	/*
475 	 * Unlike various other drivers, this driver will never
476 	 * deallocate TTYs.  This means it's safe to temporarily unlock
477 	 * the TTY when handling ioctls.
478 	 */
479 	tty_unlock(tp);
480 	error = tm->tm_class->tc_ioctl(tm, cmd, data, td);
481 	tty_lock(tp);
482 	if ((error == 0) && (cmd == CONS_CLRHIST)) {
483 		/*
484 		 * Scrollback history has been successfully cleared,
485 		 * so reset the cursor position to the top left of the screen.
486 		 */
487 		teken_pos_t p;
488 		p.tp_row = 0;
489 		p.tp_col = 0;
490 		teken_set_cursor(&tm->tm_emulator, &p);
491 	}
492 	return (error);
493 }
494 
495 static int
496 termtty_mmap(struct tty *tp, vm_ooffset_t offset, vm_paddr_t * paddr,
497     int nprot, vm_memattr_t *memattr)
498 {
499 	struct terminal *tm = tty_softc(tp);
500 
501 	return (tm->tm_class->tc_mmap(tm, offset, paddr, nprot, memattr));
502 }
503 
504 /*
505  * Binding with the kernel and debug console.
506  */
507 
508 static cn_probe_t	termcn_cnprobe;
509 static cn_init_t	termcn_cninit;
510 static cn_term_t	termcn_cnterm;
511 static cn_getc_t	termcn_cngetc;
512 static cn_putc_t	termcn_cnputc;
513 static cn_grab_t	termcn_cngrab;
514 static cn_ungrab_t	termcn_cnungrab;
515 
516 const struct consdev_ops termcn_cnops = {
517 	.cn_probe	= termcn_cnprobe,
518 	.cn_init	= termcn_cninit,
519 	.cn_term	= termcn_cnterm,
520 	.cn_getc	= termcn_cngetc,
521 	.cn_putc	= termcn_cnputc,
522 	.cn_grab	= termcn_cngrab,
523 	.cn_ungrab	= termcn_cnungrab,
524 };
525 
526 void
527 termcn_cnregister(struct terminal *tm)
528 {
529 	struct consdev *cp;
530 
531 	cp = tm->consdev;
532 	if (cp == NULL) {
533 		cp = malloc(sizeof(struct consdev), M_TERMINAL,
534 		    M_WAITOK|M_ZERO);
535 		cp->cn_ops = &termcn_cnops;
536 		cp->cn_arg = tm;
537 		cp->cn_pri = CN_INTERNAL;
538 		sprintf(cp->cn_name, "ttyv0");
539 
540 		tm->tm_flags = TF_CONS;
541 		tm->consdev = cp;
542 
543 		terminal_init(tm);
544 	}
545 
546 	/* Attach terminal as console. */
547 	cnadd(cp);
548 }
549 
550 static void
551 termcn_cngrab(struct consdev *cp)
552 {
553 	struct terminal *tm = cp->cn_arg;
554 
555 	tm->tm_class->tc_cngrab(tm);
556 }
557 
558 static void
559 termcn_cnungrab(struct consdev *cp)
560 {
561 	struct terminal *tm = cp->cn_arg;
562 
563 	tm->tm_class->tc_cnungrab(tm);
564 }
565 
566 static void
567 termcn_cnprobe(struct consdev *cp)
568 {
569 	struct terminal *tm = cp->cn_arg;
570 
571 	if (tm == NULL) {
572 		cp->cn_pri = CN_DEAD;
573 		return;
574 	}
575 
576 	tm->consdev = cp;
577 	terminal_init(tm);
578 
579 	tm->tm_class->tc_cnprobe(tm, cp);
580 }
581 
582 static void
583 termcn_cninit(struct consdev *cp)
584 {
585 
586 }
587 
588 static void
589 termcn_cnterm(struct consdev *cp)
590 {
591 
592 }
593 
594 static int
595 termcn_cngetc(struct consdev *cp)
596 {
597 	struct terminal *tm = cp->cn_arg;
598 
599 	return (tm->tm_class->tc_cngetc(tm));
600 }
601 
602 static void
603 termcn_cnputc(struct consdev *cp, int c)
604 {
605 	struct terminal *tm = cp->cn_arg;
606 	teken_attr_t backup;
607 	char cv = c;
608 
609 	TERMINAL_LOCK_CONS(tm);
610 	if (!(tm->tm_flags & TF_MUTE)) {
611 		backup = *teken_get_curattr(&tm->tm_emulator);
612 		teken_set_curattr(&tm->tm_emulator, &kernel_message);
613 		teken_input(&tm->tm_emulator, &cv, 1);
614 		teken_set_curattr(&tm->tm_emulator, &backup);
615 		tm->tm_class->tc_done(tm);
616 	}
617 	TERMINAL_UNLOCK_CONS(tm);
618 }
619 
620 /*
621  * Binding with the terminal emulator.
622  */
623 
624 static void
625 termteken_bell(void *softc)
626 {
627 	struct terminal *tm = softc;
628 
629 	tm->tm_flags |= TF_BELL;
630 }
631 
632 static void
633 termteken_cursor(void *softc, const teken_pos_t *p)
634 {
635 	struct terminal *tm = softc;
636 
637 	tm->tm_class->tc_cursor(tm, p);
638 }
639 
640 static void
641 termteken_putchar(void *softc, const teken_pos_t *p, teken_char_t c,
642     const teken_attr_t *a)
643 {
644 	struct terminal *tm = softc;
645 
646 	tm->tm_class->tc_putchar(tm, p, TCHAR_CREATE(c, a));
647 }
648 
649 static void
650 termteken_fill(void *softc, const teken_rect_t *r, teken_char_t c,
651     const teken_attr_t *a)
652 {
653 	struct terminal *tm = softc;
654 
655 	tm->tm_class->tc_fill(tm, r, TCHAR_CREATE(c, a));
656 }
657 
658 static void
659 termteken_copy(void *softc, const teken_rect_t *r, const teken_pos_t *p)
660 {
661 	struct terminal *tm = softc;
662 
663 	tm->tm_class->tc_copy(tm, r, p);
664 }
665 
666 static void
667 termteken_pre_input(void *softc)
668 {
669 	struct terminal *tm = softc;
670 
671 	tm->tm_class->tc_pre_input(tm);
672 }
673 
674 static void
675 termteken_post_input(void *softc)
676 {
677 	struct terminal *tm = softc;
678 
679 	tm->tm_class->tc_post_input(tm);
680 }
681 
682 static void
683 termteken_param(void *softc, int cmd, unsigned int arg)
684 {
685 	struct terminal *tm = softc;
686 
687 	tm->tm_class->tc_param(tm, cmd, arg);
688 }
689 
690 static void
691 termteken_respond(void *softc, const void *buf, size_t len)
692 {
693 #if 0
694 	struct terminal *tm = softc;
695 	struct tty *tp;
696 
697 	/*
698 	 * Only inject a response into the TTY if the data actually
699 	 * originated from the TTY.
700 	 *
701 	 * XXX: This cannot be done right now.  The TTY could pick up
702 	 * other locks.  It could also in theory cause loops, when the
703 	 * TTY performs echoing of a command that generates even more
704 	 * input.
705 	 */
706 	tp = tm->tm_tty;
707 	if (tp == NULL)
708 		return;
709 
710 	ttydisc_rint_simple(tp, buf, len);
711 	ttydisc_rint_done(tp);
712 #endif
713 }
714