src/i2c_temperature/driver/i2c_temperature.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 "i2c_temperature.h"

#include <fidl/fuchsia.examples.i2c.temperature/cpp/wire.h>
#include <lib/driver2/service_client.h>

#include "constants.h"
#include "temperature_server.h"

namespace i2c_temperature {

zx::result<> I2cTemperatureDriver::Start() {
  // Connect to the I2C bus controller.
  auto channel_result = SetupI2cChannel();
  if (channel_result.is_error()) {
    return channel_result.take_error();
  }

  // Serve the fuchsia.examples.i2c.temperature/Device protocol to clients through the
  // fuchsia.examples.i2c.temperature/Service wrapper.
  driver::ServiceInstanceHandler handler;
  fuchsia_examples_i2c_temperature::Service::Handler service(&handler);

  auto result = service.add_device(
      [this](fidl::ServerEnd<fuchsia_examples_i2c_temperature::Device> request) -> void {
        I2cTemperatureServer::BindDeviceClient(dispatcher(), &logger(), i2c_channel_,
                                               std::move(request));
      });
  ZX_ASSERT(result.is_ok());

  result = context().outgoing()->AddService<fuchsia_examples_i2c_temperature::Service>(
      std::move(handler));
  if (result.is_error()) {
    FDF_SLOG(ERROR, "Failed to add service", KV("status", result.status_string()));
    return result.take_error();
  }

  // Reset the sensor.
  auto write_result = i2c_channel_->Write16(kSoftResetCommand);
  if (write_result.is_error()) {
    FDF_SLOG(ERROR, "Failed to send reset command: ", KV("status", write_result.status_string()));
    return write_result.take_error();
  }

  // Read the initial temperature value.
  auto read_result = i2c_channel_->Read16();
  if (read_result.is_error()) {
    FDF_SLOG(ERROR, "Failed to read temperature: ", KV("status", read_result.status_string()));
    return read_result.take_error();
  }

  uint32_t temperature = read_result.value();
  FDF_SLOG(INFO, "I2C temperature: ", KV("temperature", temperature));

  return zx::ok();
}

// Connect to the `fuchsia.hardware.i2c/Device` protocol offered by the parent device node.
zx::result<> I2cTemperatureDriver::SetupI2cChannel() {
  auto client_endpoint =
      driver::Connect<fuchsia_hardware_i2c::Service::Device>(*context().incoming(), "default");
  if (client_endpoint.status_value() != ZX_OK) {
    FDF_SLOG(ERROR, "Failed to setup I2cChannel", KV("status", client_endpoint.status_string()));
    return client_endpoint.take_error();
  }

  auto i2c_client = fidl::WireClient(std::move(*client_endpoint), dispatcher());
  i2c_channel_ = std::make_shared<I2cChannel>(std::move(i2c_client));
  return zx::ok();
}

}  // namespace i2c_temperature

FUCHSIA_DRIVER_RECORD_CPP_V2(driver::Record<i2c_temperature::I2cTemperatureDriver>);