146 lines
4 KiB
C
146 lines
4 KiB
C
/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*-
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*
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* Copyright (C) 2018 Benjamin Berg <bberg@redhat.com>
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*
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* Licensed under the GNU General Public License Version 2
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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
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* GNU 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include "config.h"
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#include <stdlib.h>
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#include <dirent.h>
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#include <errno.h>
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#include <string.h>
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#include <libgen.h>
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#include <stdio.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <unistd.h>
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#define GSD_BACKLIGHT_HELPER_EXIT_CODE_SUCCESS 0
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#define GSD_BACKLIGHT_HELPER_EXIT_CODE_FAILED 1
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#define GSD_BACKLIGHT_HELPER_EXIT_CODE_ARGUMENTS_INVALID 3
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#define GSD_BACKLIGHT_HELPER_EXIT_CODE_INVALID_USER 4
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#ifndef __linux__
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#error "gsd-backlight-helper does not work on non-Linux"
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#endif
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static void
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usage(int argc, char *argv[])
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{
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fprintf (stderr, "Usage: %s device brightness\n", argv[0]);
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fprintf (stderr, " device: The backlight directory starting with \"/sys/class/backlight/\"\n");
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fprintf (stderr, " brightness: The new brightness to write\n");
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}
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int
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main (int argc, char *argv[])
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{
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char tmp[512];
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const char *device = NULL;
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int fd, len, res;
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int uid, euid;
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int brightness;
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int result = GSD_BACKLIGHT_HELPER_EXIT_CODE_FAILED;
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DIR *dp = NULL;
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struct dirent *ep;
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/* check calling UID */
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uid = getuid ();
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euid = geteuid ();
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if (uid != 0 || euid != 0) {
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fprintf (stderr, "This program can only be used by the root user\n");
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result = GSD_BACKLIGHT_HELPER_EXIT_CODE_INVALID_USER;
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goto done;
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}
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if (argc != 3) {
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fprintf (stderr, "Error: Need to be called with exactly two arguments\n");
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usage (argc, argv);
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result = GSD_BACKLIGHT_HELPER_EXIT_CODE_ARGUMENTS_INVALID;
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goto done;
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}
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errno = 0;
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brightness = strtol (argv[2], NULL, 0);
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if (errno) {
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fprintf (stderr, "Error: Invalid brightness argument (%d: %s)\n", errno, strerror (errno));
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usage (argc, argv);
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goto done;
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}
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dp = opendir ("/sys/class/backlight");
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if (dp == NULL) {
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fprintf (stderr, "Error: Could not open /sys/class/backlight (%d: %s)\n", errno, strerror (errno));
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result = GSD_BACKLIGHT_HELPER_EXIT_CODE_FAILED;
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goto done;
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}
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device = argv[1];
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while ((ep = readdir (dp))) {
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char *path;
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if (ep->d_name[0] == '.')
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continue;
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/* Leave room for "/brightness" */
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snprintf (tmp, sizeof(tmp) - 11, "/sys/class/backlight/%s", ep->d_name);
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path = realpath (tmp, NULL);
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if (path && device && strcmp (path, device) == 0) {
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free (path);
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strcat (tmp, "/brightness");
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fd = open (tmp, O_WRONLY);
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if (fd < 0) {
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fprintf (stderr, "Error: Could not open brightness sysfs file (%d: %s)\n", errno, strerror(errno));
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result = GSD_BACKLIGHT_HELPER_EXIT_CODE_FAILED;
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goto done;
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}
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len = snprintf (tmp, sizeof(tmp), "%d", brightness);
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if ((res = write (fd, tmp, len)) != len) {
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if (res == -1)
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fprintf (stderr, "Error: Writing to file (%d: %s)\n", errno, strerror(errno));
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else
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fprintf (stderr, "Error: Wrote the wrong length (%d of %d bytes)!\n", res, len);
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close (fd);
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result = GSD_BACKLIGHT_HELPER_EXIT_CODE_FAILED;
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goto done;
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}
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close (fd);
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result = GSD_BACKLIGHT_HELPER_EXIT_CODE_SUCCESS;
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goto done;
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} else {
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free (path);
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}
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}
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result = GSD_BACKLIGHT_HELPER_EXIT_CODE_FAILED;
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fprintf (stderr, "Error: Could not find the specified backlight \"%s\"\n", argv[1]);
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done:
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if (dp)
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closedir (dp);
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return result;
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}
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