--- /dev/null
+#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", 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 checkdir(int rp, char *dir)
+{
+ char path[256], line[256];
+ FILE *fp;
+ int rv;
+ size_t ln;
+
+ 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 || ((ln = strlen(line)) < 1) || (line[ln - 1] != '\n'))
+ errx(1, "gpio%i: could not read direction", rp);
+ line[ln - 1] = 0;
+ if(strcmp(line, dir)) {
+ if(preserve)
+ errx(2, "gpio%i: direction not set to %s", rp, dir);
+ if((fp = fopen(path, "w")) == NULL)
+ err(1, "%s", path);
+ fprintf(fp, "%s\n", dir); fflush(fp);
+ if(ferror(fp))
+ errx(1, "gpio%i: could not set to direction to %s", rp, dir);
+ fclose(fp);
+ }
+}
+
+static void setport(int p, int v)
+{
+ char path[256];
+ FILE *fp;
+ int rp;
+
+ if((rp = mappin(p)) < 0)
+ errx(1, "%i: no such port", p);
+ checkdir(rp, "out");
+ 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 int getport(int p)
+{
+ char path[256], line[256], *ep;
+ FILE *fp;
+ int rv, rp;
+ size_t ln;
+
+ if((rp = mappin(p)) < 0)
+ errx(1, "%i: no such port", p);
+ checkdir(rp, "in");
+ sprintf(path, "/sys/class/gpio/gpio%i/value", rp);
+ if((fp = fopen(path, "r")) == NULL)
+ err(1, "%s", path);
+ rv = !!fgets(line, sizeof(line), fp);
+ fclose(fp);
+ if(!rv || ((ln = strlen(line)) < 1) || (line[ln - 1] != '\n'))
+ errx(1, "gpio%i: could not read direction", rp);
+ line[ln - 1] = 0;
+ rv = (int)strtol(line, &ep, 10);
+ if(*ep)
+ errx(1, "gpio%i: unexpected contents: %s", rp, line);
+ return(rv);
+}
+
+static void usage(FILE *out)
+{
+ fprintf(out, "usage: gpio [-hip] {PORT=VAL|PORT==VAL|PORT?}...\n");
+}
+
+int main(int argc, char **argv)
+{
+ int c, i, port, val;
+ char *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++) {
+ port = strtol(argv[i], &e, 10);
+ if((e > argv[i]) && (e[0] == '=') && (e[1] == '=')) {
+ val = strtol(e + 2, &e, 10);
+ if(*e)
+ errx(1, "gpio: %s: not of the form PORT==VAL", argv[i]);
+ export(port);
+ return(getport(port) != val);
+ } else if((e > argv[i]) && (e[0] == '=')) {
+ val = strtol(e + 1, &e, 10);
+ if(*e)
+ errx(1, "gpio: %s: not of the form PORT=VAL", argv[i]);
+ export(port);
+ setport(port, val);
+ } else if((e > argv[i]) && (e[0] == '?') && !e[1]) {
+ export(port);
+ printf("%i\n", getport(port));
+ } else {
+ errx(1, "gpio: %s: not a valid argument", argv[i]);
+ }
+ }
+ return(0);
+}
+
+/*
+ * Local Variables:
+ * compile-command: "gcc -Wall -g -O2 -march=native -c -o gpio.o gpio.c && gcc -o gpio gpio.o"
+ * End:
+ */