1 files changed, 149 insertions, 0 deletions
diff --git a/plugins/power/gsd-backlight-helper.c b/plugins/power/gsd-backlight-helper.c
new file mode 100644
index 0000000..f0fbbb5
--- /dev/null
+++ b/plugins/power/gsd-backlight-helper.c
@@ -0,0 +1,149 @@
+/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*-
+ *
+ * Copyright (C) 2018 Benjamin Berg <bberg@redhat.com>
+ *
+ * Licensed under the GNU General Public License Version 2
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "config.h"
+
+#include <stdlib.h>
+#include <dirent.h>
+#include <errno.h>
+#include <string.h>
+#include <libgen.h>
+#include <stdio.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#define GSD_BACKLIGHT_HELPER_EXIT_CODE_SUCCESS			0
+#define GSD_BACKLIGHT_HELPER_EXIT_CODE_FAILED			1
+#define GSD_BACKLIGHT_HELPER_EXIT_CODE_ARGUMENTS_INVALID	3
+#define GSD_BACKLIGHT_HELPER_EXIT_CODE_INVALID_USER		4
+
+#ifndef __linux__
+#error "gsd-backlight-helper does not work on non-Linux"
+#endif
+
+static void
+usage(int argc, char *argv[])
+{
+	fprintf (stderr, "Usage: %s device brightness\n", argv[0]);
+	fprintf (stderr, "  device:      The backlight directory starting with \"/sys/class/backlight/\"\n");
+	fprintf (stderr, "  brightness:  The new brightness to write\n");
+}
+
+int
+main (int argc, char *argv[])
+{
+	char tmp[512];
+	char *device = NULL;
+	int fd, len, res;
+	int uid, euid;
+	int brightness;
+	int result = GSD_BACKLIGHT_HELPER_EXIT_CODE_FAILED;
+	DIR *dp = NULL;
+	struct dirent *ep;
+
+	/* check calling UID */
+	uid = getuid ();
+	euid = geteuid ();
+	if (uid != 0 || euid != 0) {
+		fprintf (stderr, "This program can only be used by the root user\n");
+		result = GSD_BACKLIGHT_HELPER_EXIT_CODE_INVALID_USER;
+		goto done;
+	}
+
+	if (argc != 3) {
+		fprintf (stderr, "Error: Need to be called with exactly two arguments\n");
+		usage (argc, argv);
+		result = GSD_BACKLIGHT_HELPER_EXIT_CODE_ARGUMENTS_INVALID;
+		goto done;
+	}
+
+	errno = 0;
+	brightness = strtol (argv[2], NULL, 0);
+	if (errno) {
+		fprintf (stderr, "Error: Invalid brightness argument (%d: %s)\n", errno, strerror (errno));
+		usage (argc, argv);
+		goto done;
+	}
+
+	dp = opendir ("/sys/class/backlight");
+	if (dp == NULL) {
+		fprintf (stderr, "Error: Could not open /sys/class/backlight (%d: %s)\n", errno, strerror (errno));
+		result = GSD_BACKLIGHT_HELPER_EXIT_CODE_FAILED;
+		goto done;
+	}
+
+	/* May be NULL if the path cannot be resolved */
+	device = realpath (argv[1], NULL);
+
+	while ((ep = readdir (dp))) {
+		char *path;
+
+		if (ep->d_name[0] == '.')
+			continue;
+
+		/* Leave room for "/brightness" */
+		snprintf (tmp, sizeof(tmp) - 11, "/sys/class/backlight/%s", ep->d_name);
+		path = realpath (tmp, NULL);
+		if (path && device && strcmp (path, device) == 0) {
+			free (path);
+			strcat (tmp, "/brightness");
+
+			fd = open (tmp, O_WRONLY);
+			if (fd < 0) {
+				fprintf (stderr, "Error: Could not open brightness sysfs file (%d: %s)\n", errno, strerror(errno));
+				result = GSD_BACKLIGHT_HELPER_EXIT_CODE_FAILED;
+				goto done;
+			}
+
+			len = snprintf (tmp, sizeof(tmp), "%d", brightness);
+			if ((res = write (fd, tmp, len)) != len) {
+				if (res == -1)
+					fprintf (stderr, "Error: Writing to file (%d: %s)\n", errno, strerror(errno));
+				else
+					fprintf (stderr, "Error: Wrote the wrong length (%d of %d bytes)!\n", res, len);
+
+				close (fd);
+				result = GSD_BACKLIGHT_HELPER_EXIT_CODE_FAILED;
+				goto done;
+			}
+			close (fd);
+
+			result = GSD_BACKLIGHT_HELPER_EXIT_CODE_SUCCESS;
+			goto done;
+		} else {
+			free (path);
+		}
+	}
+
+	result = GSD_BACKLIGHT_HELPER_EXIT_CODE_FAILED;
+	fprintf (stderr, "Error: Could not find the specified backlight \"%s\"\n", argv[1]);
+
+done:
+	if (device)
+		free (device);
+	if (dp)
+		closedir (dp);
+
+	return result;
+}
+