gpio: chardev interface / multiple gpio support for sysfs

Signed-off-by: Mihai Stefanescu <mihai.t.gh.stefanescu@gmail.com>
Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>

examples/gpio_multiple_rw.c

@@ -0,0 +1,103 @@
+/* This currently works only on Intel Joule Platform. */
+
+#include <stdio.h>
+#include <signal.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+
+#include "mraa/gpio.h"
+
+int running = 0;
+
+void
+sig_handler(int signo)
+{
+    if (signo == SIGINT) {
+        printf("Closing down nicely\n");
+        running = -1;
+    }
+}
+
+int main(int argc, char** argv)
+{
+    mraa_result_t r = MRAA_SUCCESS;
+    /* These are Joule's onboard LED's. */
+    int default_joule_leds[] = {100, 101, 102, 103};
+    int *gpio_pins;
+    int num_pins;
+    int *input_values, *output_values;
+
+    printf("Provide int arg(s) if you want to toggle gpio pins other than Joule's onboard LED's\n");
+
+    if (argc < 2) {
+        gpio_pins = default_joule_leds;
+        num_pins = 4;
+    } else {
+        num_pins = argc - 1;
+        gpio_pins = malloc(num_pins * sizeof(int));
+
+        for (int i = 0; i < num_pins; ++i) {
+            gpio_pins[i] = strtol(argv[i+1], NULL, 10);
+        }
+    }
+
+    /* Allocate input and output values arrays. */
+    input_values = malloc(num_pins * sizeof(int));
+    output_values = malloc(num_pins * sizeof(int));
+
+    mraa_init();
+    fprintf(stdout, "MRAA Version: %s\nStarting program...\n", mraa_get_version());
+
+    mraa_gpio_context gpio = mraa_gpio_init_multi(gpio_pins, num_pins);
+    if (gpio == NULL) {
+        fprintf(stderr, "Error during gpio initialization\n");
+        exit(1);
+    }
+
+    r = mraa_gpio_dir(gpio, MRAA_GPIO_OUT);
+    if (r != MRAA_SUCCESS) {
+        mraa_result_print(r);
+    }
+
+    signal(SIGINT, sig_handler);
+
+    /* Set input values first. */
+    memset(input_values, 0, num_pins * sizeof(int));
+
+    while (running == 0) {
+        r = mraa_gpio_write_multi(gpio, input_values);
+
+        sleep(1);
+
+        if (r != MRAA_SUCCESS) {
+            mraa_result_print(r);
+        } else {
+            r = mraa_gpio_read_multi(gpio, output_values);
+            if (r != MRAA_SUCCESS) {
+                mraa_result_print(r);
+            }
+        }
+
+        for (int i = 0; i < num_pins; ++i) {
+            input_values[i] = (input_values[i] + 1) % 2;
+        }
+    }
+
+    memset(input_values, 0, num_pins * sizeof(int));
+    mraa_gpio_write_multi(gpio, input_values);
+
+    r = mraa_gpio_close(gpio);
+    if (r != MRAA_SUCCESS) {
+        mraa_result_print(r);
+    }
+
+    /* Cleanup. */
+    if (argc >= 2) {
+       free(gpio_pins);
+    }
+    free(input_values);
+    free(output_values);
+
+    return r;
+}