src/i2c_temperature/client/main.cc

// Copyright 2022 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include <ctype.h>
#include <dirent.h>
#include <fcntl.h>
#include <fidl/examples.i2c.temperature/cpp/wire.h>
#include <getopt.h>
#include <lib/fdio/directory.h>
#include <libgen.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>

constexpr char kDevicePath[] = "/dev/i2c-temperature-controller/i2c-temperature";

int usage(const char* cmd) {
  fprintf(stderr,
          "\nInteract with the temperature sensor device:\n"
          "   %s read                       Reads the current temperature value\n"
          "   %s reset                      Reset the temperature sensor\n"
          "   %s help                       Print this message\n",
          cmd, cmd, cmd);
  return -1;
}

// Returns "true" if the argument matches the prefix.
// In this case, moves the argument past the prefix.
bool prefix_match(const char** arg, const char* prefix) {
  if (!strncmp(*arg, prefix, strlen(prefix))) {
    *arg += strlen(prefix);
    return true;
  }
  return false;
}

// Open a FIDL client connection to the examples.i2c.temperature/Device
fidl::WireSyncClient<examples_i2c_temperature::Device> OpenDevice() {
  int device = open(kDevicePath, O_RDWR);
  if (device < 0) {
    fprintf(stderr, "Failed to open temperature device: %s\n", strerror(errno));
    return {};
  }
  fidl::ClientEnd<examples_i2c_temperature::Device> client_end;
  zx_status_t st = fdio_get_service_handle(device, client_end.channel().reset_and_get_address());
  if (st != ZX_OK) {
    fprintf(stderr, "Failed to get service handle: %s\n", zx_status_get_string(st));
    return {};
  }
  return fidl::WireSyncClient(std::move(client_end));
}

// Send a command to measure the temperature and print the result.
// Returns 0 on success.
int read_temperature() {
  auto client = OpenDevice();
  if (!client.is_valid()) {
    return -1;
  }

  auto temperature_result = client->ReadTemperature();
  if (!temperature_result.ok()) {
    fprintf(stderr, "Error: failed to read temperature result: %s\n",
            zx_status_get_string(temperature_result.status()));
    return -1;
  }

  printf("Current temperature: %f\n", temperature_result->value()->temperature);
  return 0;
}

// Send a command to reset the temperature sensor.
// Returns 0 on success.
int reset_temperature() {
  auto client = OpenDevice();
  if (!client.is_valid()) {
    return -1;
  }

  auto reset_result = client->ResetSensor();
  if (!reset_result.ok()) {
    fprintf(stderr, "Error: failed to reset temperature sensor: %s\n",
            zx_status_get_string(reset_result.status()));
    return -1;
  }

  printf("Sensor reset successfully\n");
  return 0;
}

int main(int argc, char* argv[]) {
  const char* cmd = basename(argv[0]);

  // If no arguments passed, bail out after dumping
  // usage information.
  if (argc < 2) {
    return usage(cmd);
  }

  const char* arg = argv[1];
  if (prefix_match(&arg, "read")) {
    return read_temperature();
  } else if (prefix_match(&arg, "reset")) {
    return reset_temperature();
  }
  return usage(cmd);
}