/*
 * (c) Bernd 'Aard' Wachter, <bwachter@lart.info>
 * You may use and redistribute this file under the terms and conditions
 * of the GNU GPL v2
 *
 * Install:
 * - Compile with cc cpu.c -o cpu
 * - Copy cpu into some directory in your searchpath (e.g. /usr/bin)
 * - Create links named clo and chi pointing to cpu
 *
 * Usage: 
 * - call cpu to view the current governor and cpu freq
 * - call clo or cpu lo to set the powersave governor
 * - call chi or cpu hi to set the performance governor
 *
 */
 
#include <fcntl.h>

#define GV_PATH "/sys/devices/system/cpu/cpu0/cpufreq/scaling_governor"
#define FQ_PATH "/sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq"

void msg(char *msg){
  write(1,msg,strlen(msg));
}

int wrgov(char *gov){
  int fd;
  if ((fd=open(GV_PATH, O_WRONLY))==-1){
    msg("Cannot open governor file\n");
    return -1;
  }
  write(fd,gov,strlen(gov));
  if (close(fd)==-1) {
    msg("Problem closing governor file\n");
    return -1;
  }
  return 0;
}

int rdgov(char *gov){
  int fd,i;
  char buf[512];
  if ((fd=open(gov, O_RDONLY))==-1){
    msg("Cannot open governor file\n");
    return -1;
  }
  if ((i=read(fd,buf,512))==-1){
    msg("Error while reading file\n");
    return -1;
  }
  buf[i]='\0';
  msg(buf);
  if (close(fd)==-1) {
    msg("Problem closing governor file\n");
    return -1;
  }
}

int main(int argc, char** argv) {
  setuid(geteuid());
  if (argv[1]==0) argv[1]="";
  if (!strcmp(argv[0],"clo") || !strcmp(argv[1],"lo")){
    msg("Setting cpu to lo\n");
    if (wrgov("powersave")==-1) return -1;
  } else if (!strcmp(argv[0],"chi") || !strcmp(argv[1],"hi")){
    msg("Setting cpu to hi\n");
    if (wrgov("performance")==-1) return -1;
  } else {
    msg("Current governor: ");
    if (rdgov(GV_PATH)==-1) return -1;
    msg("Current freq: ");
    if (rdgov(FQ_PATH)==-1) return -1;
  }
}