Added rpi gpio program.

[utils.git] / gpio.c

#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <err.h>

static void setport(int p, int v)
{
    char path[256], line[256];
    FILE *fp;
    int rv;
    
    sprintf(path, "/sys/class/gpio/gpio%i/direction", p);
    if((fp = fopen(path, "r")) == NULL)
	err(1, "%s", path);
    rv = !!fgets(line, sizeof(line), fp);
    fclose(fp);
    if(!rv || strcmp(line, "out\n")) {
	if((fp = fopen(path, "w")) == NULL)
	    err(1, "%s", path);
	fprintf(fp, "out\n"); fflush(fp);
	if(ferror(fp))
	    errx(1, "gpio%i: could not set to output", p);
	fclose(fp);
    }
    sprintf(path, "/sys/class/gpio/gpio%i/value", p);
    if((fp = fopen(path, "w")) == NULL)
	err(1, "%s", path);
    fprintf(fp, "%i\n", v); fflush(fp);
    if(ferror(fp))
	errx(1, "gpio%i: could not set value", p);
    fclose(fp);
}

int main(int argc, char **argv)
{
    int i, port, val;
    char *p, *e;
    
    for(i = 1; i < argc; i++) {
	if((p = strchr(argv[i], '=')) == NULL) {
	    fprintf(stderr, "gpio: %s: not of the form PORT=VAL\n", argv[i]);
	    exit(1);
	}
	port = strtol(argv[i], &e, 10);
	if(e != p) {
	    fprintf(stderr, "gpio: %s: not of the form PORT=VAL\n", argv[i]);
	    exit(1);
	}
	val = strtol(p + 1, &e, 10);
	if(*e) {
	    fprintf(stderr, "gpio: %s: not of the form PORT=VAL\n", argv[i]);
	    exit(1);
	}
	setport(port, val);
    }
    return(0);
}