#include <stdio.h>
#include <stdlib.h>

#define PATH "/sys/devices/pci0000:00/0000:00:02.0/config"
#define STEP 24

/*
Written by Krzysztof Sielużycki, KSieluzycki@gmail.com

!!! Use at your own risk !!!

How to install:
1) adjust PATH. You can check your device address by running lspci
2) compile: gcc bright.c -o b
    of course you can use any desired name instead of b ;)
3) change owner to root: chown root:root b
4) set suid (app require root privileges): chmod +s b
5) move to /usr/bin: mv b /usr/bin/b
6) adjust key shortcuts in your window manager.
    For example, in gnome, it's in start->system->preferences.
    Create one shortcut for /usr/bin/d u, and another one
    for /usr/bin/b d

Usage:

b u - increase brightness by STEP value
b d - decrease by STEP value
b s - show brightness level
b x <value> - set brightness to value x, where
    x is a integer between 0 and 255.
    0 means backlight off.
*/


signed int check_level() {
    int current_level;
    FILE * cfg;
    cfg=fopen(PATH,"rb");
    if(cfg) {
	fseek(cfg,244,0);
	current_level=fgetc(cfg);
	fclose(cfg);
	return current_level;
    }
    else {return -1;}
}
signed int set_level(int value) {
    if(value<0 || value>255) {
	printf("Error\n");
	return -1;
    }
    FILE * cfg;
    cfg=fopen(PATH,"r+b");
    if(cfg) {
	fseek(cfg,244,0);
	fputc(value,cfg);
	fclose(cfg);
	return 0;
    }
    else {return -1;}

}
int main(int argc, char * argv[]) {
    int current_level=3;
    if(argc!=1) {
	if((current_level=check_level())!=-1) {
	    if(*argv[1]=='u') {
		if(current_level<255-STEP) {
		    if(set_level(current_level+STEP)==-1) {
			printf("Error setting level.\n");
		    }
		}
		else {printf("%s\n","Maximum reached");}
	    }
	    else if(*argv[1]=='d') {
		if(current_level>0+STEP) {
		    if(set_level(current_level-STEP)==-1) {
			printf("Error setting level.\n");
		    }
		}
		else {printf("%s\n","Minimum reached");}
	    }
	    else if(*argv[1]=='s') {
		printf("%s%d\n","Current brightness level: ",current_level);
	    }
	    else if(*argv[1]=='x' && argc>2) {
		set_level(atoi(argv[2]));
	    }
	    else {printf("Invalid argument\n");}
	}
	else {
	    printf("%s\n","Error checking brightness level.");
	}
    }
    else {
	printf("%s\n","Usage: b [u|d|s|x]");
    }
    return 0;
}