pmbus.hpp

#pragma once

#include <experimental/filesystem>
#include <string>
#include <vector>

namespace witherspoon
{
namespace pmbus
{

namespace fs = std::experimental::filesystem;

// The file name Linux uses to capture the STATUS_WORD from pmbus.
constexpr auto STATUS_WORD = "status0";

// The file name Linux uses to capture the STATUS_INPUT from pmbus.
constexpr auto STATUS_INPUT = "status0_input";

// Voltage out status.
// Overvoltage fault or warning, Undervoltage fault or warning, maximum or
// minimum warning, ....
// Uses Page substitution
constexpr auto STATUS_VOUT = "statusP_vout";

// Current output status bits.
constexpr auto STATUS_IOUT = "status0_iout";

// Manufacturing specific status bits
constexpr auto STATUS_MFR = "status0_mfr";

namespace status_word
{
constexpr auto VOUT_FAULT = 0x8000;

// The IBM CFF power supply driver does map this bit to power1_alarm in the
// hwmon space, but since the other bits that need to be checked do not have
// a similar mapping, the code will just read STATUS_WORD and use bit masking
// to see if the INPUT FAULT OR WARNING bit is on.
constexpr auto INPUT_FAULT_WARN = 0x2000;

// The bit mask representing the POWER_GOOD Negated bit of the STATUS_WORD.
constexpr auto POWER_GOOD_NEGATED = 0x0800;

// The bit mask representing the UNITI_IS_OFF bit of the STATUS_WORD.
constexpr auto UNIT_IS_OFF = 0x0040;

// Bit 5 of the STATUS_BYTE, or lower byte of STATUS_WORD is used to indicate
// an output overvoltage fault.
constexpr auto VOUT_OV_FAULT = 0x0020;

// The bit mask representing that an output overcurrent fault has occurred.
constexpr auto IOUT_OC_FAULT = 0x0010;

// The IBM CFF power supply driver does map this bit to in1_alarm, however,
// since a number of the other bits are not mapped that way for STATUS_WORD,
// this code will just read the entire STATUS_WORD and use bit masking to find
// out if that fault is on.
constexpr auto VIN_UV_FAULT = 0x0008;

}

/**
 * If the access should be done in the base
 * device directory, the hwmon directory, the
 * pmbus debug directory, or the device debug
 * directory.
 */
enum class Type
{
    Base,
    Hwmon,
    Debug,
    DeviceDebug
};

/**
 * @class PMBus
 *
 * This class is an interface to communicating with PMBus devices
 * by reading and writing sysfs files.
 *
 * Based on the Type parameter, the accesses can either be done
 * in the base device directory (the one passed into the constructor),
 * or in the hwmon directory for the device.
 */
class PMBus
{
    public:

        PMBus() = delete;
        ~PMBus() = default;
        PMBus(const PMBus&) = default;
        PMBus& operator=(const PMBus&) = default;
        PMBus(PMBus&&) = default;
        PMBus& operator=(PMBus&&) = default;

        /**
         * Constructor
         *
         * @param[in] path - path to the sysfs directory
         */
        PMBus(const std::string& path) :
            basePath(path)
        {
            findHwmonDir();
        }

        /**
         * Constructor
         *
         * This version is required when DeviceDebug
         * access will be used.
         *
         * @param[in] path - path to the sysfs directory
         * @param[in] driverName - the device driver name
         * @param[in] instance - chip instance number
         */
        PMBus(const std::string& path,
              const std::string& driverName,
              size_t instance) :
            basePath(path),
            driverName(driverName),
            instance(instance)
        {
            findHwmonDir();
        }

        /**
         * Reads a file in sysfs that represents a single bit,
         * therefore doing a PMBus read.
         *
         * @param[in] name - path concatenated to
         *                   basePath to read
         * @param[in] type - Path type
         *
         * @return bool - false if result was 0, else true
         */
        bool readBit(const std::string& name, Type type);

        /**
         * Reads a file in sysfs that represents a single bit,
         * where the page number passed in is substituted
         * into the name in place of the 'P' character in it.
         *
         * @param[in] name - path concatenated to
         *                   basePath to read
         * @param[in] page - page number
         * @param[in] type - Path type
         *
         * @return bool - false if result was 0, else true
         */
        bool readBitInPage(const std::string& name,
                           size_t page,
                           Type type);
        /**
         * Read byte(s) from file in sysfs.
         *
         * @param[in] name   - path concatenated to basePath to read
         * @param[in] type   - Path type
         *
         * @return uint64_t - Up to 8 bytes of data read from file.
         */
        uint64_t read(const std::string& name, Type type);

        /**
         * Writes an integer value to the file, therefore doing
         * a PMBus write.
         *
         * @param[in] name - path concatenated to
         *                   basePath to write
         * @param[in] value - the value to write
         * @param[in] type - Path type
         */
        void write(const std::string& name, int value, Type type);

        /**
         * Returns the sysfs base path of this device
         */
        inline const auto& path() const
        {
            return basePath;
        }

        /**
         * Replaces the 'P' in the string passed in with
         * the page number passed in.
         *
         * For example:
         *   insertPageNum("inP_enable", 42)
         *   returns "in42_enable"
         *
         * @param[in] templateName - the name string, with a 'P' in it
         * @param[in] page - the page number to insert where the P was
         *
         * @return string - the new string with the page number in it
         */
        static std::string insertPageNum(const std::string& templateName,
                                         size_t page);

        /**
         * Finds the path relative to basePath to the hwmon directory
         * for the device and stores it in hwmonRelPath.
         */
        void findHwmonDir();

        /**
         * Returns the path to use for the passed in type.
         *
         * @param[in] type - Path type
         *
         * @return fs::path - the full path
         */
        fs::path getPath(Type type);

    private:

        /**
         * The sysfs device path
         */
        fs::path basePath;

        /**
         * The directory name under the basePath hwmon directory
         */
        fs::path hwmonDir;

        /**
         * The device driver name.  Used for finding the device
         * debug directory.  Not required if that directory
         * isn't used.
         */
        std::string driverName;

        /**
         * The device instance number.
         *
         * Used in conjuction with the driver name for finding
         * the debug directory.  Not required if that directory
         * isn't used.
         */
        size_t instance = 0;

        /**
         * The pmbus debug path with status files
         */
        const fs::path debugPath = "/sys/kernel/debug/";

};

}
}