xref: /freebsd/sys/kern/subr_terminal.c (revision b670c9bafc0e31c7609969bf374b2e80bdc00211) 
1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause
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/param.h>
32 #include <sys/cons.h>
33 #include <sys/consio.h>
34 #include <sys/kernel.h>
35 #include <sys/lock.h>
36 #include <sys/malloc.h>
37 #include <sys/mutex.h>
38 #include <sys/stdarg.h>
39 #include <sys/systm.h>
40 #include <sys/terminal.h>
41 #include <sys/tty.h>
42 
43 static MALLOC_DEFINE(M_TERMINAL, "terminal", "terminal device");
44 
45 /*
46  * Locking.
47  *
48  * Normally we don't need to lock down the terminal emulator, because
49  * the TTY lock is already held when calling teken_input().
50  * Unfortunately this is not the case when the terminal acts as a
51  * console device, because cnputc() can be called at the same time.
52  * This means terminals may need to be locked down using a spin lock.
53  */
54 #define	TERMINAL_LOCK(tm)	do {					\
55 	if ((tm)->tm_flags & TF_CONS)					\
56 		mtx_lock_spin(&(tm)->tm_mtx);				\
57 	else if ((tm)->tm_tty != NULL)					\
58 		tty_lock((tm)->tm_tty);					\
59 } while (0)
60 #define	TERMINAL_UNLOCK(tm)	do {					\
61 	if ((tm)->tm_flags & TF_CONS)					\
62 		mtx_unlock_spin(&(tm)->tm_mtx);				\
63 	else if ((tm)->tm_tty != NULL)					\
64 		tty_unlock((tm)->tm_tty);				\
65 } while (0)
66 #define	TERMINAL_LOCK_TTY(tm)	do {					\
67 	if ((tm)->tm_flags & TF_CONS)					\
68 		mtx_lock_spin(&(tm)->tm_mtx);				\
69 } while (0)
70 #define	TERMINAL_UNLOCK_TTY(tm)	do {					\
71 	if ((tm)->tm_flags & TF_CONS)					\
72 		mtx_unlock_spin(&(tm)->tm_mtx);				\
73 } while (0)
74 #define	TERMINAL_LOCK_CONS(tm)		mtx_lock_spin(&(tm)->tm_mtx)
75 #define	TERMINAL_UNLOCK_CONS(tm)	mtx_unlock_spin(&(tm)->tm_mtx)
76 
77 /*
78  * TTY routines.
79  */
80 
81 static tsw_open_t	termtty_open;
82 static tsw_close_t	termtty_close;
83 static tsw_outwakeup_t	termtty_outwakeup;
84 static tsw_ioctl_t	termtty_ioctl;
85 static tsw_mmap_t	termtty_mmap;
86 
87 static struct ttydevsw terminal_tty_class = {
88 	.tsw_open	= termtty_open,
89 	.tsw_close	= termtty_close,
90 	.tsw_outwakeup	= termtty_outwakeup,
91 	.tsw_ioctl	= termtty_ioctl,
92 	.tsw_mmap	= termtty_mmap,
93 };
94 
95 /*
96  * Terminal emulator routines.
97  */
98 
99 static tf_bell_t	termteken_bell;
100 static tf_cursor_t	termteken_cursor;
101 static tf_putchar_t	termteken_putchar;
102 static tf_fill_t	termteken_fill;
103 static tf_copy_t	termteken_copy;
104 static tf_pre_input_t	termteken_pre_input;
105 static tf_post_input_t	termteken_post_input;
106 static tf_param_t	termteken_param;
107 static tf_respond_t	termteken_respond;
108 
109 static teken_funcs_t terminal_drawmethods = {
110 	.tf_bell	= termteken_bell,
111 	.tf_cursor	= termteken_cursor,
112 	.tf_putchar	= termteken_putchar,
113 	.tf_fill	= termteken_fill,
114 	.tf_copy	= termteken_copy,
115 	.tf_pre_input	= termteken_pre_input,
116 	.tf_post_input	= termteken_post_input,
117 	.tf_param	= termteken_param,
118 	.tf_respond	= termteken_respond,
119 };
120 
121 /* Kernel message formatting. */
122 static teken_attr_t kernel_message = {
123 	.ta_fgcolor	= TCHAR_FGCOLOR(TERMINAL_KERN_ATTR),
124 	.ta_bgcolor	= TCHAR_BGCOLOR(TERMINAL_KERN_ATTR),
125 	.ta_format	= TCHAR_FORMAT(TERMINAL_KERN_ATTR)
126 };
127 
128 static teken_attr_t default_message = {
129 	.ta_fgcolor	= TCHAR_FGCOLOR(TERMINAL_NORM_ATTR),
130 	.ta_bgcolor	= TCHAR_BGCOLOR(TERMINAL_NORM_ATTR),
131 	.ta_format	= TCHAR_FORMAT(TERMINAL_NORM_ATTR)
132 };
133 
134 /* Fudge fg brightness as TF_BOLD (shifted). */
135 #define	TCOLOR_FG_FUDGED(color) __extension__ ({			\
136 	teken_color_t _c;						\
137 									\
138 	_c = (color);							\
139 	TCOLOR_FG(_c & 7) | ((_c & 8) << 18);				\
140 })
141 
142 /* Fudge bg brightness as TF_BLINK (shifted). */
143 #define	TCOLOR_BG_FUDGED(color) __extension__ ({			\
144 	teken_color_t _c;						\
145 									\
146 	_c = (color);							\
147 	TCOLOR_BG(_c & 7) | ((_c & 8) << 20);				\
148 })
149 
150 #define	TCOLOR_256TO16(color) __extension__ ({				\
151 	teken_color_t _c;						\
152 									\
153 	_c = (color);							\
154 	if (_c >= 16)							\
155 		_c = teken_256to16(_c);					\
156 	_c;								\
157 })
158 
159 #define	TCHAR_CREATE(c, a)	((c) | TFORMAT((a)->ta_format) |	\
160 	TCOLOR_FG_FUDGED(TCOLOR_256TO16((a)->ta_fgcolor)) |		\
161 	TCOLOR_BG_FUDGED(TCOLOR_256TO16((a)->ta_bgcolor)))
162 
163 static void
164 terminal_init(struct terminal *tm)
165 {
166 	int fg, bg;
167 
168 	if (tm->tm_flags & TF_CONS)
169 		mtx_init(&tm->tm_mtx, "trmlck", NULL, MTX_SPIN);
170 
171 	teken_init(&tm->tm_emulator, &terminal_drawmethods, tm);
172 
173 	fg = bg = -1;
174 	TUNABLE_INT_FETCH("teken.fg_color", &fg);
175 	TUNABLE_INT_FETCH("teken.bg_color", &bg);
176 
177 	if (fg != -1) {
178 		default_message.ta_fgcolor = fg;
179 		kernel_message.ta_fgcolor = fg;
180 	}
181 	if (bg != -1) {
182 		default_message.ta_bgcolor = bg;
183 		kernel_message.ta_bgcolor = bg;
184 	}
185 
186 	if (default_message.ta_bgcolor == TC_WHITE) {
187 		default_message.ta_bgcolor |= TC_LIGHT;
188 		kernel_message.ta_bgcolor |= TC_LIGHT;
189 	}
190 
191 	if (default_message.ta_bgcolor == TC_BLACK &&
192 	    default_message.ta_fgcolor < TC_NCOLORS)
193 		kernel_message.ta_fgcolor |= TC_LIGHT;
194 	teken_set_defattr(&tm->tm_emulator, &default_message);
195 }
196 
197 struct terminal *
198 terminal_alloc(const struct terminal_class *tc, void *softc)
199 {
200 	struct terminal *tm;
201 
202 	tm = malloc(sizeof(struct terminal), M_TERMINAL, M_WAITOK|M_ZERO);
203 	terminal_init(tm);
204 
205 	tm->tm_class = tc;
206 	tm->tm_softc = softc;
207 
208 	return (tm);
209 }
210 
211 static void
212 terminal_sync_ttysize(struct terminal *tm)
213 {
214 	struct tty *tp;
215 
216 	tp = tm->tm_tty;
217 	if (tp == NULL)
218 		return;
219 
220 	tty_lock(tp);
221 	tty_set_winsize(tp, &tm->tm_winsize);
222 	tty_unlock(tp);
223 }
224 
225 void
226 terminal_maketty(struct terminal *tm, const char *fmt, ...)
227 {
228 	struct tty *tp;
229 	char name[8];
230 	va_list ap;
231 
232 	va_start(ap, fmt);
233 	vsnrprintf(name, sizeof name, 32, fmt, ap);
234 	va_end(ap);
235 
236 	tp = tty_alloc(&terminal_tty_class, tm);
237 	tty_makedev(tp, NULL, "%s", name);
238 	tm->tm_tty = tp;
239 	terminal_sync_ttysize(tm);
240 }
241 
242 void
243 terminal_set_cursor(struct terminal *tm, const term_pos_t *pos)
244 {
245 
246 	teken_set_cursor(&tm->tm_emulator, pos);
247 }
248 
249 void
250 terminal_set_winsize_blank(struct terminal *tm, const struct winsize *size,
251     int blank, const term_attr_t *attr)
252 {
253 	term_rect_t r;
254 
255 	tm->tm_winsize = *size;
256 
257 	r.tr_begin.tp_row = r.tr_begin.tp_col = 0;
258 	r.tr_end.tp_row = size->ws_row;
259 	r.tr_end.tp_col = size->ws_col;
260 
261 	TERMINAL_LOCK(tm);
262 	if (blank == 0)
263 		teken_set_winsize_noreset(&tm->tm_emulator, &r.tr_end);
264 	else
265 		teken_set_winsize(&tm->tm_emulator, &r.tr_end);
266 	TERMINAL_UNLOCK(tm);
267 
268 	if ((blank != 0) && !(tm->tm_flags & TF_MUTE))
269 		tm->tm_class->tc_fill(tm, &r,
270 		    TCHAR_CREATE((teken_char_t)' ', attr));
271 
272 	terminal_sync_ttysize(tm);
273 }
274 
275 void
276 terminal_set_winsize(struct terminal *tm, const struct winsize *size)
277 {
278 
279 	terminal_set_winsize_blank(tm, size, 1,
280 	    (const term_attr_t *)&default_message);
281 }
282 
283 /*
284  * XXX: This function is a kludge.  Drivers like vt(4) need to
285  * temporarily stop input when resizing, etc.  This should ideally be
286  * handled within the driver.
287  */
288 
289 void
290 terminal_mute(struct terminal *tm, int yes)
291 {
292 
293 	TERMINAL_LOCK(tm);
294 	if (yes)
295 		tm->tm_flags |= TF_MUTE;
296 	else
297 		tm->tm_flags &= ~TF_MUTE;
298 	TERMINAL_UNLOCK(tm);
299 }
300 
301 void
302 terminal_input_char(struct terminal *tm, term_char_t c)
303 {
304 	struct tty *tp;
305 
306 	tp = tm->tm_tty;
307 	if (tp == NULL)
308 		return;
309 
310 	/*
311 	 * Strip off any attributes. Also ignore input of second part of
312 	 * CJK fullwidth characters, as we don't want to return these
313 	 * characters twice.
314 	 */
315 	if (TCHAR_FORMAT(c) & TF_CJK_RIGHT)
316 		return;
317 	c = TCHAR_CHARACTER(c);
318 
319 	tty_lock(tp);
320 	/*
321 	 * Conversion to UTF-8.
322 	 */
323 	if (c < 0x80) {
324 		ttydisc_rint(tp, c, 0);
325 	} else if (c < 0x800) {
326 		char str[2] = {
327 			0xc0 | (c >> 6),
328 			0x80 | (c & 0x3f)
329 		};
330 
331 		ttydisc_rint_simple(tp, str, sizeof str);
332 	} else if (c < 0x10000) {
333 		char str[3] = {
334 			0xe0 | (c >> 12),
335 			0x80 | ((c >> 6) & 0x3f),
336 			0x80 | (c & 0x3f)
337 		};
338 
339 		ttydisc_rint_simple(tp, str, sizeof str);
340 	} else {
341 		char str[4] = {
342 			0xf0 | (c >> 18),
343 			0x80 | ((c >> 12) & 0x3f),
344 			0x80 | ((c >> 6) & 0x3f),
345 			0x80 | (c & 0x3f)
346 		};
347 
348 		ttydisc_rint_simple(tp, str, sizeof str);
349 	}
350 	ttydisc_rint_done(tp);
351 	tty_unlock(tp);
352 }
353 
354 void
355 terminal_input_raw(struct terminal *tm, char c)
356 {
357 	struct tty *tp;
358 
359 	tp = tm->tm_tty;
360 	if (tp == NULL)
361 		return;
362 
363 	tty_lock(tp);
364 	ttydisc_rint(tp, c, 0);
365 	ttydisc_rint_done(tp);
366 	tty_unlock(tp);
367 }
368 
369 void
370 terminal_input_special(struct terminal *tm, unsigned int k)
371 {
372 	struct tty *tp;
373 	const char *str;
374 
375 	tp = tm->tm_tty;
376 	if (tp == NULL)
377 		return;
378 
379 	str = teken_get_sequence(&tm->tm_emulator, k);
380 	if (str == NULL)
381 		return;
382 
383 	tty_lock(tp);
384 	ttydisc_rint_simple(tp, str, strlen(str));
385 	ttydisc_rint_done(tp);
386 	tty_unlock(tp);
387 }
388 
389 /*
390  * Binding with the TTY layer.
391  */
392 
393 static int
394 termtty_open(struct tty *tp)
395 {
396 	struct terminal *tm = tty_softc(tp);
397 
398 	tm->tm_class->tc_opened(tm, 1);
399 	return (0);
400 }
401 
402 static void
403 termtty_close(struct tty *tp)
404 {
405 	struct terminal *tm = tty_softc(tp);
406 
407 	tm->tm_class->tc_opened(tm, 0);
408 }
409 
410 static void
411 termtty_outwakeup(struct tty *tp)
412 {
413 	struct terminal *tm = tty_softc(tp);
414 	char obuf[128];
415 	size_t olen;
416 	unsigned int flags = 0;
417 
418 	while ((olen = ttydisc_getc(tp, obuf, sizeof obuf)) > 0) {
419 		TERMINAL_LOCK_TTY(tm);
420 		if (!(tm->tm_flags & TF_MUTE)) {
421 			tm->tm_flags &= ~TF_BELL;
422 			teken_input(&tm->tm_emulator, obuf, olen);
423 			flags |= tm->tm_flags;
424 		}
425 		TERMINAL_UNLOCK_TTY(tm);
426 	}
427 
428 	TERMINAL_LOCK_TTY(tm);
429 	if (!(tm->tm_flags & TF_MUTE))
430 		tm->tm_class->tc_done(tm);
431 	TERMINAL_UNLOCK_TTY(tm);
432 	if (flags & TF_BELL)
433 		tm->tm_class->tc_bell(tm);
434 }
435 
436 static int
437 termtty_ioctl(struct tty *tp, u_long cmd, caddr_t data, struct thread *td)
438 {
439 	struct terminal *tm = tty_softc(tp);
440 	int error;
441 
442 	switch (cmd) {
443 	case CONS_GETINFO: {
444 		vid_info_t *vi = (vid_info_t *)data;
445 		const teken_pos_t *p;
446 		int fg, bg;
447 
448 		if (vi->size != sizeof(vid_info_t))
449 			return (EINVAL);
450 
451 		/* Already help the console driver by filling in some data. */
452 		p = teken_get_cursor(&tm->tm_emulator);
453 		vi->mv_row = p->tp_row;
454 		vi->mv_col = p->tp_col;
455 
456 		p = teken_get_winsize(&tm->tm_emulator);
457 		vi->mv_rsz = p->tp_row;
458 		vi->mv_csz = p->tp_col;
459 
460 		teken_get_defattr_cons25(&tm->tm_emulator, &fg, &bg);
461 		vi->mv_norm.fore = fg;
462 		vi->mv_norm.back = bg;
463 		/* XXX: keep vidcontrol happy; bold backgrounds. */
464 		vi->mv_rev.fore = bg;
465 		vi->mv_rev.back = fg & 0x7;
466 		break;
467 	}
468 	}
469 
470 	/*
471 	 * Unlike various other drivers, this driver will never
472 	 * deallocate TTYs.  This means it's safe to temporarily unlock
473 	 * the TTY when handling ioctls.
474 	 */
475 	tty_unlock(tp);
476 	error = tm->tm_class->tc_ioctl(tm, cmd, data, td);
477 	tty_lock(tp);
478 	if ((error == 0) && (cmd == CONS_CLRHIST)) {
479 		/*
480 		 * Scrollback history has been successfully cleared,
481 		 * so reset the cursor position to the top left of the screen.
482 		 */
483 		teken_pos_t p;
484 		p.tp_row = 0;
485 		p.tp_col = 0;
486 		teken_set_cursor(&tm->tm_emulator, &p);
487 	}
488 	return (error);
489 }
490 
491 static int
492 termtty_mmap(struct tty *tp, vm_ooffset_t offset, vm_paddr_t * paddr,
493     int nprot, vm_memattr_t *memattr)
494 {
495 	struct terminal *tm = tty_softc(tp);
496 
497 	return (tm->tm_class->tc_mmap(tm, offset, paddr, nprot, memattr));
498 }
499 
500 /*
501  * Binding with the kernel and debug console.
502  */
503 
504 static cn_probe_t	termcn_cnprobe;
505 static cn_init_t	termcn_cninit;
506 static cn_term_t	termcn_cnterm;
507 static cn_getc_t	termcn_cngetc;
508 static cn_putc_t	termcn_cnputc;
509 static cn_grab_t	termcn_cngrab;
510 static cn_ungrab_t	termcn_cnungrab;
511 
512 const struct consdev_ops termcn_cnops = {
513 	.cn_probe	= termcn_cnprobe,
514 	.cn_init	= termcn_cninit,
515 	.cn_term	= termcn_cnterm,
516 	.cn_getc	= termcn_cngetc,
517 	.cn_putc	= termcn_cnputc,
518 	.cn_grab	= termcn_cngrab,
519 	.cn_ungrab	= termcn_cnungrab,
520 };
521 
522 void
523 termcn_cnregister(struct terminal *tm)
524 {
525 	struct consdev *cp;
526 
527 	cp = tm->consdev;
528 	if (cp == NULL) {
529 		cp = malloc(sizeof(struct consdev), M_TERMINAL,
530 		    M_WAITOK|M_ZERO);
531 		cp->cn_ops = &termcn_cnops;
532 		cp->cn_arg = tm;
533 		cp->cn_pri = CN_INTERNAL;
534 		sprintf(cp->cn_name, "ttyv0");
535 
536 		tm->tm_flags = TF_CONS;
537 		tm->consdev = cp;
538 
539 		terminal_init(tm);
540 	}
541 
542 	/* Attach terminal as console. */
543 	cnadd(cp);
544 }
545 
546 static void
547 termcn_cngrab(struct consdev *cp)
548 {
549 	struct terminal *tm = cp->cn_arg;
550 
551 	tm->tm_class->tc_cngrab(tm);
552 }
553 
554 static void
555 termcn_cnungrab(struct consdev *cp)
556 {
557 	struct terminal *tm = cp->cn_arg;
558 
559 	tm->tm_class->tc_cnungrab(tm);
560 }
561 
562 static void
563 termcn_cnprobe(struct consdev *cp)
564 {
565 	struct terminal *tm = cp->cn_arg;
566 
567 	if (tm == NULL) {
568 		cp->cn_pri = CN_DEAD;
569 		return;
570 	}
571 
572 	tm->consdev = cp;
573 	terminal_init(tm);
574 
575 	tm->tm_class->tc_cnprobe(tm, cp);
576 }
577 
578 static void
579 termcn_cninit(struct consdev *cp)
580 {
581 
582 }
583 
584 static void
585 termcn_cnterm(struct consdev *cp)
586 {
587 
588 }
589 
590 static int
591 termcn_cngetc(struct consdev *cp)
592 {
593 	struct terminal *tm = cp->cn_arg;
594 
595 	return (tm->tm_class->tc_cngetc(tm));
596 }
597 
598 static void
599 termcn_cnputc(struct consdev *cp, int c)
600 {
601 	struct terminal *tm = cp->cn_arg;
602 	teken_attr_t backup;
603 	char cv = c;
604 
605 	TERMINAL_LOCK_CONS(tm);
606 	if (!(tm->tm_flags & TF_MUTE)) {
607 		backup = *teken_get_curattr(&tm->tm_emulator);
608 		teken_set_curattr(&tm->tm_emulator, &kernel_message);
609 		teken_input(&tm->tm_emulator, &cv, 1);
610 		teken_set_curattr(&tm->tm_emulator, &backup);
611 		tm->tm_class->tc_done(tm);
612 	}
613 	TERMINAL_UNLOCK_CONS(tm);
614 }
615 
616 /*
617  * Binding with the terminal emulator.
618  */
619 
620 static void
621 termteken_bell(void *softc)
622 {
623 	struct terminal *tm = softc;
624 
625 	tm->tm_flags |= TF_BELL;
626 }
627 
628 static void
629 termteken_cursor(void *softc, const teken_pos_t *p)
630 {
631 	struct terminal *tm = softc;
632 
633 	tm->tm_class->tc_cursor(tm, p);
634 }
635 
636 static void
637 termteken_putchar(void *softc, const teken_pos_t *p, teken_char_t c,
638     const teken_attr_t *a)
639 {
640 	struct terminal *tm = softc;
641 
642 	tm->tm_class->tc_putchar(tm, p, TCHAR_CREATE(c, a));
643 }
644 
645 static void
646 termteken_fill(void *softc, const teken_rect_t *r, teken_char_t c,
647     const teken_attr_t *a)
648 {
649 	struct terminal *tm = softc;
650 
651 	tm->tm_class->tc_fill(tm, r, TCHAR_CREATE(c, a));
652 }
653 
654 static void
655 termteken_copy(void *softc, const teken_rect_t *r, const teken_pos_t *p)
656 {
657 	struct terminal *tm = softc;
658 
659 	tm->tm_class->tc_copy(tm, r, p);
660 }
661 
662 static void
663 termteken_pre_input(void *softc)
664 {
665 	struct terminal *tm = softc;
666 
667 	tm->tm_class->tc_pre_input(tm);
668 }
669 
670 static void
671 termteken_post_input(void *softc)
672 {
673 	struct terminal *tm = softc;
674 
675 	tm->tm_class->tc_post_input(tm);
676 }
677 
678 static void
679 termteken_param(void *softc, int cmd, unsigned int arg)
680 {
681 	struct terminal *tm = softc;
682 
683 	tm->tm_class->tc_param(tm, cmd, arg);
684 }
685 
686 static void
687 termteken_respond(void *softc, const void *buf, size_t len)
688 {
689 #if 0
690 	struct terminal *tm = softc;
691 	struct tty *tp;
692 
693 	/*
694 	 * Only inject a response into the TTY if the data actually
695 	 * originated from the TTY.
696 	 *
697 	 * XXX: This cannot be done right now.  The TTY could pick up
698 	 * other locks.  It could also in theory cause loops, when the
699 	 * TTY performs echoing of a command that generates even more
700 	 * input.
701 	 */
702 	tp = tm->tm_tty;
703 	if (tp == NULL)
704 		return;
705 
706 	ttydisc_rint_simple(tp, buf, len);
707 	ttydisc_rint_done(tp);
708 #endif
709 }
710