tlbmc/sensors/hwmon_input_device.cc

#include "tlbmc/sensors/hwmon_input_device.h"

#include <array>
#include <cstddef>
#include <exception>
#include <fstream>
#include <ios>
#include <memory>
#include <string>
#include <string_view>
#include <utility>

#include "absl/functional/any_invocable.h"
#include "absl/log/log.h"
#include "boost/asio.hpp"  // NOLINT: boost::asio is commonly used in BMC
#include "boost/asio/error.hpp"  // NOLINT
#include "boost/asio/random_access_file.hpp"  // NOLINT: boost::asio is commonly used in BMC
#include "boost/filesystem.hpp"  // NOLINT: boost::filesystem is commonly used in BMC
#include "boost/filesystem/operations.hpp"  // NOLINT
#include "boost/system/detail/error_code.hpp"  // NOLINT: boost::asio is commonly used in BMC

namespace milotic_tlbmc {

HwmonInputDevice::HwmonInputDevice(
    const std::shared_ptr<boost::asio::io_context>& io_context,
    std::string_view input_dev_path)
    : io_context_(io_context), input_dev_path_(input_dev_path) {
  // Prod kernel doesn't support io_uring yet. To make continuous build and test
  // happy, we disable io_uring and use synchronous file read.
  // On BMC kernel, io_uring will be supported by default.
  // On cloudtop or workstation, add `--test_strategy=local` to your blaze
  // command to enable io_uring.
  try {
    // Explicitly specify the O_NONBLOCK flag to avoid blocking the input file
    // reading, needed for some kernel versions. (b/421908876)
    io_uring_input_device_ = std::make_shared<boost::asio::random_access_file>(
        *io_context_, input_dev_path_,
        boost::asio::random_access_file::read_only |
            static_cast<boost::asio::random_access_file::flags>(O_NONBLOCK));
  } catch (const std::exception& e) {
    io_uring_input_device_ = nullptr;
    LOG(WARNING) << "Failed to create io_uring based random_access_file for "
                 << input_dev_path_ << ": " << e.what()
                 << " . Fall back to ifstream.";
    ifstream_input_device_ = std::ifstream(input_dev_path_);
  }
}

HwmonInputDevice::~HwmonInputDevice() {
  ifstream_input_device_.close();
  if (io_uring_input_device_) {
    boost::asio::post(*io_context_,
                      [io_uring_input_device = io_uring_input_device_] {
                        io_uring_input_device->close();
                      });
  }
}

void HwmonInputDevice::ReadAndProcess(
    absl::AnyInvocable<void(const boost::system::error_code&, size_t)> callback,
    std::array<char, 128>& read_buffer) {
  if (io_uring_input_device_ != nullptr) {
    io_uring_input_device_->async_read_some_at(
        0, boost::asio::buffer(read_buffer),
        [callback = std::move(callback)](const boost::system::error_code& error,
                                         size_t bytes_read) mutable {
          callback(error, bytes_read);
        });
    return;
  }
  ifstream_input_device_.read(read_buffer.data(),
                              static_cast<std::streamsize>(read_buffer.size()));
  callback(boost::system::error_code(), read_buffer.size());
}

}  // namespace milotic_tlbmc