gpio: Auto-export ports.

[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 const int bmap[] = {
    -1,
    -1, -1,  2, -1,  3, -1,  4, 14, -1, 15, 17, 18, 27, -1, 22, 23, -1, 24, 10, -1,
     9, 25, 11,  8, -1,  7, -1, -1,  5, -1,  6, 12, 13, -1, 19, 16, 21, 20, -1, 21,
};
static const int imap[] = {
    -1, -1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13,
    14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, 27,
};
static const int *umap = bmap;
static int mapn = sizeof(bmap) / sizeof(*bmap);
static int preserve = 0;

static int mappin(int num)
{
    if((num < 0) || (num >= mapn))
	return(-1);
    return(umap[num]);
}

static void export(int p)
{
    char path[256];
    FILE *fp;
    int rp;
    
    if((rp = mappin(p)) < 0)
	errx(1, "%i: no such port\n", p);
    sprintf(path, "/sys/class/gpio/gpio%i", rp);
    if(!access(path, R_OK | X_OK))
	return;
    if(preserve)
	errx(2, "gpio%i: not exported", rp);
    sprintf(path, "/sys/class/gpio/export");
    if((fp = fopen(path, "w")) == NULL)
	err(1, "%s", path);
    fprintf(fp, "%i\n", rp); fflush(fp);
    if(ferror(fp))
	errx(1, "gpio%i: could not export", rp);
    fclose(fp);
    sprintf(path, "/sys/class/gpio/gpio%i", rp);
    if(access(path, R_OK | X_OK))
	errx(1, "gpio%i: still not available after export", rp);
}

static void setport(int p, int v)
{
    char path[256], line[256];
    FILE *fp;
    int rv, rp;
    
    if((rp = mappin(p)) < 0)
	errx(1, "%i: no such port\n", p);
    sprintf(path, "/sys/class/gpio/gpio%i/direction", rp);
    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(preserve)
	    errx(2, "gpio%i: not set to output", rp);
	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", rp);
	fclose(fp);
    }
    sprintf(path, "/sys/class/gpio/gpio%i/value", rp);
    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", rp);
    fclose(fp);
}

static void usage(FILE *out)
{
    fprintf(out, "usage: gpio [-hip] PORT=VAL...\n");
}

int main(int argc, char **argv)
{
    int c, i, port, val;
    char *p, *e;
    
    while((c = getopt(argc, argv, "hip")) >= 0) {
	switch(c) {
	case 'h':
	    usage(stdout);
	    return(0);
	case 'i':
	    umap = imap;
	    mapn = sizeof(imap) / sizeof(*imap);
	    break;
	case 'p':
	    preserve = 1;
	    break;
	default:
	    usage(stderr);
	    return(1);
	}
    }
    if(optind >= argc) {
	usage(stderr);
	return(1);
    }
    for(i = optind; 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);
	}
	export(port);
	setport(port, val);
    }
    return(0);
}

/*
 * Local Variables:
 * compile-command: "gcc -Wall -g -O2 -march=native -o gpio gpio.c"
 * End:
 */