125 lines
2.6 KiB
C
125 lines
2.6 KiB
C
/* vi: set sw=4 ts=4: */
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/*
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* Utility routines.
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*
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* Copyright (C) many different people. If you wrote this, please
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* acknowledge your work.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#include <stdio.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <sys/ioctl.h>
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#include "libbb.h"
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/* From <linux/kd.h> */
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static const int KDGKBTYPE = 0x4B33; /* get keyboard type */
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static const int KB_84 = 0x01;
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static const int KB_101 = 0x02; /* this is what we always answer */
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int is_a_console(int fd)
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{
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char arg;
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arg = 0;
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return (ioctl(fd, KDGKBTYPE, &arg) == 0
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&& ((arg == KB_101) || (arg == KB_84)));
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}
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static int open_a_console(char *fnam)
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{
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int fd;
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/* try read-only */
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fd = open(fnam, O_RDWR);
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/* if failed, try read-only */
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if (fd < 0 && errno == EACCES)
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fd = open(fnam, O_RDONLY);
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/* if failed, try write-only */
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if (fd < 0 && errno == EACCES)
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fd = open(fnam, O_WRONLY);
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/* if failed, fail */
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if (fd < 0)
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return -1;
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/* if not a console, fail */
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if (!is_a_console(fd)) {
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close(fd);
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return -1;
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}
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/* success */
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return fd;
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}
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/*
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* Get an fd for use with kbd/console ioctls.
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* We try several things because opening /dev/console will fail
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* if someone else used X (which does a chown on /dev/console).
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*
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* if tty_name is non-NULL, try this one instead.
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*/
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int get_console_fd(char *tty_name)
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{
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int fd;
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if (tty_name) {
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if (-1 == (fd = open_a_console(tty_name)))
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return -1;
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else
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return fd;
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}
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fd = open_a_console(CURRENT_TTY);
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if (fd >= 0)
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return fd;
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fd = open_a_console(CURRENT_VC);
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if (fd >= 0)
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return fd;
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fd = open_a_console(CONSOLE_DEV);
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if (fd >= 0)
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return fd;
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for (fd = 0; fd < 3; fd++)
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if (is_a_console(fd))
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return fd;
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error_msg("Couldn't get a file descriptor referring to the console");
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return -1; /* total failure */
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}
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/* END CODE */
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/*
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Local Variables:
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c-file-style: "linux"
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c-basic-offset: 4
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tab-width: 4
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End:
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*/
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