1/* vi: set sw=4 ts=4: */
2/*
3 * Utility routines.
4 *
5 * Copyright (C) tons of folks.  Tracking down who wrote what
6 * isn't something I'm going to worry about...  If you wrote something
7 * here, please feel free to acknowledge your work.
8 *
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License as published by
11 * the Free Software Foundation; either version 2 of the License, or
12 * (at your option) any later version.
13 *
14 * This program is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 * General Public License for more details.
18 *
19 * You should have received a copy of the GNU General Public License
20 * along with this program; if not, write to the Free Software
21 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
22 *
23 * Based in part on code from sash, Copyright (c) 1999 by David I. Bell
24 * Permission has been granted to redistribute this code under the GPL.
25 *
26 */
27
28#include <stdio.h>
29#include <errno.h>
30#include <fcntl.h>
31#include <unistd.h>
32#include <sys/ioctl.h>
33#include "libbb.h"
34
35
36
37
38
39/* From <linux/kd.h> */
40static const int KDGKBTYPE = 0x4B33;  /* get keyboard type */
41static const int KB_84 = 0x01;
42static const int KB_101 = 0x02;    /* this is what we always answer */
43
44int is_a_console(int fd)
45{
46	char arg;
47
48	arg = 0;
49	return (ioctl(fd, KDGKBTYPE, &arg) == 0
50			&& ((arg == KB_101) || (arg == KB_84)));
51}
52
53static int open_a_console(char *fnam)
54{
55	int fd;
56
57	/* try read-only */
58	fd = open(fnam, O_RDWR);
59
60	/* if failed, try read-only */
61	if (fd < 0 && errno == EACCES)
62		fd = open(fnam, O_RDONLY);
63
64	/* if failed, try write-only */
65	if (fd < 0 && errno == EACCES)
66		fd = open(fnam, O_WRONLY);
67
68	/* if failed, fail */
69	if (fd < 0)
70		return -1;
71
72	/* if not a console, fail */
73	if (!is_a_console(fd)) {
74		close(fd);
75		return -1;
76	}
77
78	/* success */
79	return fd;
80}
81
82/*
83 * Get an fd for use with kbd/console ioctls.
84 * We try several things because opening /dev/console will fail
85 * if someone else used X (which does a chown on /dev/console).
86 *
87 * if tty_name is non-NULL, try this one instead.
88 */
89
90int get_console_fd(char *tty_name)
91{
92	int fd;
93
94	if (tty_name) {
95		if (-1 == (fd = open_a_console(tty_name)))
96			return -1;
97		else
98			return fd;
99	}
100
101	fd = open_a_console(CURRENT_TTY);
102	if (fd >= 0)
103		return fd;
104
105	fd = open_a_console(CURRENT_VC);
106	if (fd >= 0)
107		return fd;
108
109	fd = open_a_console(CONSOLE_DEV);
110	if (fd >= 0)
111		return fd;
112
113	for (fd = 0; fd < 3; fd++)
114		if (is_a_console(fd))
115			return fd;
116
117	error_msg("Couldn't get a file descriptor referring to the console");
118	return -1;					/* total failure */
119}
120
121
122/* END CODE */
123/*
124Local Variables:
125c-file-style: "linux"
126c-basic-offset: 4
127tab-width: 4
128End:
129*/
130