sysfs.cpp

/**
 * Copyright © 2016 IBM Corporation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#include <cstdlib>
#include <experimental/filesystem>
#include <memory>
#include <phosphor-logging/log.hpp>
#include "sysfs.hpp"
#include "util.hpp"

std::string findHwmon(const std::string& ofNode)
{
    namespace fs = std::experimental::filesystem;
    static constexpr auto hwmonRoot = "/sys/class/hwmon";
    static constexpr auto ofRoot = "/sys/firmware/devicetree/base";

    fs::path fullOfPath{ofRoot};
    fullOfPath /= ofNode;

    for (const auto& hwmonInst : fs::directory_iterator(hwmonRoot))
    {
        auto path = hwmonInst.path();
        path /= "of_node";

        if (fs::canonical(path) != fullOfPath)
        {
            continue;
        }

        return hwmonInst.path();
    }

    return std::string();
}

int readSysfsWithCallout(const std::string& root,
                         const std::string& instance,
                         const std::string& type,
                         const std::string& id,
                         const std::string& sensor)
{
    namespace fs = std::experimental::filesystem;

    int value = 0;
    std::ifstream ifs;
    fs::path instancePath{root};
    instancePath /= instance;
    std::string fullPath = make_sysfs_path(instancePath,
                                           type, id, sensor);

    ifs.exceptions(std::ifstream::failbit
                   | std::ifstream::badbit
                   | std::ifstream::eofbit);
    try
    {
        ifs.open(fullPath);
        ifs >> value;
    }
    catch (const std::exception& e)
    {
        // Too many GCC bugs (53984, 66145) to do
        // this the right way...

        // errno should still reflect the error from the failing open
        // or read system calls that got us here.
        auto rc = errno;
        instancePath /= "device";
        phosphor::logging::log<phosphor::logging::level::ERR>(
            strerror(rc),
            phosphor::logging::entry(
                "CALLOUT_DEVICE_PATH=%s",
                fs::canonical(instancePath).c_str()),
            phosphor::logging::entry("CALLOUT_ERRNO=%d", rc));
        exit(EXIT_FAILURE);
    }

    return value;
}

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