1/* vi: set sw=4 ts=4: */
2/*
3 * Utility routines.
4 *
5 * Copyright (C) many different people.  If you wrote this, please
6 * acknowledge your work.
7 *
8 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
9 */
10
11//#include <sys/ioctl.h>
12#include "libbb.h"
13
14
15/* From <linux/kd.h> */
16enum { KDGKBTYPE = 0x4B33 };  /* get keyboard type */
17
18
19static int open_a_console(const char *fnam)
20{
21	int fd;
22
23	/* try read-write */
24	fd = open(fnam, O_RDWR);
25
26	/* if failed, try read-only */
27	if (fd < 0 && errno == EACCES)
28		fd = open(fnam, O_RDONLY);
29
30	/* if failed, try write-only */
31	if (fd < 0 && errno == EACCES)
32		fd = open(fnam, O_WRONLY);
33
34	return fd;
35}
36
37/*
38 * Get an fd for use with kbd/console ioctls.
39 * We try several things because opening /dev/console will fail
40 * if someone else used X (which does a chown on /dev/console).
41 */
42
43int get_console_fd(void)
44{
45	static const char *const console_names[] = {
46		DEV_CONSOLE, CURRENT_VC, CURRENT_TTY
47	};
48
49	int fd;
50
51	for (fd = 2; fd >= 0; fd--) {
52		int fd4name;
53		int choice_fd;
54		char arg;
55
56		fd4name = open_a_console(console_names[fd]);
57 chk_std:
58		choice_fd = (fd4name >= 0 ? fd4name : fd);
59
60		arg = 0;
61		if (ioctl(choice_fd, KDGKBTYPE, &arg) == 0)
62			return choice_fd;
63		if (fd4name >= 0) {
64			close(fd4name);
65			fd4name = -1;
66			goto chk_std;
67		}
68	}
69
70	bb_error_msg("cannot get file descriptor referring to console");
71	return fd;                      /* total failure */
72}
73