sysfs.hpp

#pragma once

#include <exception>
#include <fstream>
#include <string>

namespace sysfs {

/**
 * @class DeviceBusyException
 *
 * An internal exception which will be thrown when
 * readSysfsWithCallout() hits an EAGAIN.  Will never bubble
 * up to terminate the application, nor does it need to be
 * reported.
 */
class DeviceBusyException : public std::runtime_error
{
    public:

        DeviceBusyException(const std::string& path) :
            std::runtime_error(path + " busy")
        {
        }
};

inline std::string make_sysfs_path(const std::string& path,
                                   const std::string& type,
                                   const std::string& id,
                                   const std::string& entry)
{
    using namespace std::literals;

    return path + "/"s + type + id + "_"s + entry;
}

/** @brief Return the path to the phandle file matching value in io-channels.
 *
 *  This function will take two passed in paths.
 *  One path is used to find the io-channels file.
 *  The other path is used to find the phandle file.
 *  The 4 byte phandle value is read from the phandle file(s).
 *  The 4 byte phandle value and 4 byte index value is read from io-channels.
 *  When a match is found, the path to the matching phandle file is returned.
 *
 *  @param[in] iochanneldir - Path to file for getting phandle from io-channels
 *  @param[in] phandledir - Path to use for reading from phandle file
 *
 *  @return Path to phandle file with value matching that in io-channels
 */
std::string findPhandleMatch(
        const std::string& iochanneldir,
        const std::string& phandledir);

/** @brief Find hwmon instances
 *
 *  Look for a matching hwmon instance given an
 *  open firmware device path.
 *
 *  @param[in] ofNode- The open firmware device path.
 *
 *  @returns[in] - The hwmon instance path or an empty
 *                 string if no match is found.
 */
std::string findHwmon(const std::string& ofNode);

/** @brief Return the path to use for a call out.
 *
 *  Return an empty string if a callout path cannot be
 *  found.
 *
 *  @param[in] instancePath - /sys/class/hwmon/hwmon<N> path.
 *
 *  @return Path to use for call out
 */
std::string findCalloutPath(const std::string& instancePath);

/** @brief Read an hwmon sysfs value.
 *
 *  Calls exit(3) with bad status on failure.
 *
 *  @param[in] root - The hwmon class root.
 *  @param[in] instance - The hwmon instance (ex. hwmon1).
 *  @param[in] type - The hwmon type (ex. temp).
 *  @param[in] id - The hwmon id (ex. 1).
 *  @param[in] sensor - The hwmon sensor (ex. input).
 *  @param[in] throwDeviceBusy - will throw a DeviceBusyException
 *             on an EAGAIN errno instead of an error log exception.
 *
 *  @returns - The read value.
 */
int readSysfsWithCallout(const std::string& root,
                         const std::string& instance,
                         const std::string& type,
                         const std::string& id,
                         const std::string& sensor,
                         bool throwDeviceBusy = true);

 /** @brief Write a hwmon sysfs value
  *
  *  Calls exit(3) with bad status on failure
  *
  *  @param[in] value - The value to be written
  *  @param[in] root - The hwmon class root.
  *  @param[in] instance - The hwmon instance (ex. hwmon1).
  *  @param[in] type - The hwmon type (ex. fan).
  *  @param[in] id - The hwmon id (ex. 1).
  *  @param[in] sensor - The hwmon sensor (ex. target).
  *
  *  @returns - The value written
  */
uint64_t writeSysfsWithCallout(const uint64_t& value,
                               const std::string& root,
                               const std::string& instance,
                               const std::string& type,
                               const std::string& id,
                               const std::string& sensor);

}

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