Øvelse 4: Linux Kernemoduler

#include <unistd.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>

#include <string.h>
#include <errno.h>


void SetLed(int hfile, char * value);

int main()
{
    char ch;
    int hBrightness=0;
    int hTrigger=0;
    
    

    char *ON = "1";
    char *OFF = "0";
    char *NONE = "none";
    char *HEARTBEAT = "heartbeat";

    enum BOOL {false=0,true} bLoop = true;

    

    if ((hBrightness = open("/sys/class/leds/led3/brightness", O_WRONLY ) ) == -1){
        printf("Error opening Brightness file: %s\n",strerror(errno));
    }
    else {
        printf("Brightness file successfully opened.\n");
    }

    if ((hTrigger = open("/sys/class/leds/led3/trigger", O_WRONLY ) ) == -1){
        printf("Error opening Trigger file: %s\n",strerror(errno));
    }
    else {
        printf("Trigger file successfully opened.\n");
    }

    //As long as 'q' is not pressed
    while ( bLoop ) {
    
        printf("Actions on LED3:\n");
        printf("\t 0 - Turn off. \n");
        printf("\t 1 - Turn on. \n");
        printf("\t h - Heartbeat. \n");
        printf("\t n - No heartbeat. \n");
        printf("\t q - Quit. \n");
        printf("Your choice: ");
        ch=getchar();
        
        switch (ch) {
            case '0' : SetLed(hBrightness,ON); break;
            case '1' : SetLed(hBrightness,OFF); break;
            case 'h' : SetLed(hTrigger,HEARTBEAT); break;
            case 'n' : SetLed(hTrigger,NONE); break;
            case 'q' : bLoop = false; break;
            default  : break;
        }    
        //empty input buffer        
        while((ch=getchar()) != '\n'){}

    

    }



    if ( close(hBrightness) != 0  ) {
        printf("Error closing Brightness file. Error: %s\n",strerror(errno));
    }
    else {
        printf("Brightness file successfully closed.\n");
    }

    if ( close(hTrigger) != 0  ) {
        printf("Error closing Trigger file. Error: %s\n",strerror(errno));
    }
    else {
        printf("Trigger file successfully closed.\n");
    }
        
    exit(0);
}


void SetLed(int hFile, char * value){
            
        int length = strlen(value);
        int nwrite;
        if ( (nwrite = write(hFile,value,length) ) != length )    
        {
            printf("Error writing to file. Error: %s.\n",nwrite,strerror(errno));
        }

}