Added udev rule and init.d script for allowing users of video group to control backlight

TODO

@@ -1,3 +1,4 @@
 Individual device control
+List devices
 Query backlight percentage (get)
 allow fade in and fade out

makefile

@@ -1,16 +1,21 @@
 .PHONY: all
 all: rexbacklight
 
-rexbacklight: rexbacklight.c
+rexbacklight: src/rexbacklight.c
-	gcc -std=c11 -O2 -Wall -Wextra -pedantic rexbacklight.c -o rexbacklight
+	gcc -std=c11 -O2 -Wall -Wextra -pedantic src/rexbacklight.c -o rexbacklight
 	strip --strip-all rexbacklight
 
 .PHONY: install
 install:
-	install -m4711 -o root -g root -s rexbacklight /usr/bin/rexbacklight
+	install -m755 -o root -g root -s rexbacklight /usr/bin/rexbacklight
+	install -m600 -o root -g root rules/91-backlight.rules /etc/udev/rules.d/91-backlight.rules
+	install -m755 -o root -g root rules/backlight /etc/init.d/backlight
 
 .PHONY: uninstall
+uninstall:
 	rm /usr/bin/rexbacklight
+	rm /etc/udev/rules.d/91-backlight.rules
+	rm /etc/init.d/backlight
 .PHONY: clean
 clean:
 	rm rexbacklight

rules/91-backlight.rules

@@ -0,0 +1,3 @@
+SUBSYSTEM=="backlight", ACTION=="add", \
+	RUN+="/bin/chgrp video %S%p/brightness", \
+	RUN+="/bin/chmod g+w %S%p/brightness"

rules/backlight

@@ -0,0 +1,13 @@
+#!/sbin/openrc-run
+#Copyright (C) 2018 rexy712
+
+start() {
+	ebegin "Forcing intel_backlight to work correctly"
+	/bin/chgrp video /sys/class/backlight/intel_backlight/brightness
+	/bin/chmod g+w /sys/class/backlight/intel_backlight/brightness
+	eend $?
+}
+
+stop() {
+	eend ${ret}
+}

src/rexbacklight.c

@@ -48,27 +48,6 @@ void usage(int exit_val){
 	exit(exit_val);
 }
 
-int check_valid_files(const char* f1, const char* f2){
-	struct stat file1, file2;
-	if(stat(f1, &file1)){
-		printf("failed to open '%s'\n", f1);
-		return -1;
-	}
-	if(stat(f2, &file2)){
-		printf("failed to open '%s'\n", f2);
-		return -1;
-	}
-	//Same device and same inode means same file
-
-	//device id
-	if(file1.st_dev != file2.st_dev)
-		return -2;
-	//inode number
-	if(file1.st_ino != file2.st_ino)
-		return -2;
-	return 0;
-}
-
 struct string_array{
 	char** list;
 	int size;
@@ -185,21 +164,6 @@ int main(int argc, char** argv){
 	else if(strlen(argv[1]) < 2)
 		usage(-1);
 
-	//Gain access to sysfs files
-	if(setuid(0)){
-		fprintf(stderr, "Unable to setuid to 0!\n");
-		return -3;
-	}
-
-	//Make sure we aren't in a chroot environment (prevents writing to a file we don't want to!)
-	if(check_valid_files("/", "/proc/1/root")){
-		fprintf(stderr, "No chroot today\n");
-		return -4;
-	}
-
-	//Now that we've verified we're in a safe environment to do the work,
-	//Let's get everything set up!
-
 	//Acquire a list of backlight devices in sysfs
 	struct string_array backlight_names = get_backlight_sources();
 	if(backlight_names.size == 0){
@@ -226,7 +190,7 @@ int main(int argc, char** argv){
 		int out = process_arg(argv[1], 0, get_brightness(backlight_file), get_brightness(max_backlight_file));
 		FILE* bright = fopen(backlight_file, "w+");
 		if(!bright){
-			fprintf(stderr, "Unable to open brightness file \"%s\" for writing!\n", backlight_file);
+			fprintf(stderr, "Unable to open brightness file \"%s%s\" for writing!\n", backlight_dir, backlight_file);
 			continue;
 		}
 		fprintf(bright, "%d", out);