diff --git a/.github/workflows/ruby.yml b/.github/workflows/ruby.yml
new file mode 100644
index 0000000..06538ff
--- /dev/null
+++ b/.github/workflows/ruby.yml
@@ -0,0 +1,20 @@
+name: Ruby
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up Ruby
+      uses: ruby/setup-ruby@v1
+      with:
+        ruby-version: '2.7'
+    - name: Build and test with Rake
+      run: |
+        gem install bundler
+        bundle install --jobs 4 --retry 3
+        bundle exec rake
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..fd54a94
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+.vscode
+*.gem
diff --git a/.rubocop.yml b/.rubocop.yml
new file mode 100644
index 0000000..fd3a646
--- /dev/null
+++ b/.rubocop.yml
@@ -0,0 +1,17 @@
+Style/Documentation:
+  Enabled: false
+
+Metrics/ClassLength:
+  Enabled: false
+
+Metrics/AbcSize:
+  Enabled: false
+
+Metrics/MethodLength:
+  Max: 25
+
+Metrics/CyclomaticComplexity:
+  Max: 10
+
+Style/PerlBackrefs:
+  Enabled: false
diff --git a/Gemfile b/Gemfile
new file mode 100644
index 0000000..b1c4c0d
--- /dev/null
+++ b/Gemfile
@@ -0,0 +1,7 @@
+source 'https://rubygems.org'
+
+gem 'minitest', '~> 5.21.2'
+gem 'rake', '~> 13.0.0'
+gem 'rubocop', '~> 1.60'
+
+gem 'open3'
diff --git a/Gemfile.lock b/Gemfile.lock
new file mode 100644
index 0000000..106af86
--- /dev/null
+++ b/Gemfile.lock
@@ -0,0 +1,44 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    ast (2.4.2)
+    json (2.7.1)
+    language_server-protocol (3.17.0.3)
+    minitest (5.21.2)
+    open3 (0.1.2)
+    parallel (1.24.0)
+    parser (3.3.0.5)
+      ast (~> 2.4.1)
+      racc
+    racc (1.7.3)
+    rainbow (3.1.1)
+    rake (13.0.6)
+    regexp_parser (2.9.0)
+    rexml (3.2.6)
+    rubocop (1.60.2)
+      json (~> 2.3)
+      language_server-protocol (>= 3.17.0)
+      parallel (~> 1.10)
+      parser (>= 3.3.0.2)
+      rainbow (>= 2.2.2, < 4.0)
+      regexp_parser (>= 1.8, < 3.0)
+      rexml (>= 3.2.5, < 4.0)
+      rubocop-ast (>= 1.30.0, < 2.0)
+      ruby-progressbar (~> 1.7)
+      unicode-display_width (>= 2.4.0, < 3.0)
+    rubocop-ast (1.30.0)
+      parser (>= 3.2.1.0)
+    ruby-progressbar (1.13.0)
+    unicode-display_width (2.5.0)
+
+PLATFORMS
+  x86_64-linux
+
+DEPENDENCIES
+  minitest (~> 5.21.2)
+  open3
+  rake (~> 13.0.0)
+  rubocop (~> 1.60)
+
+BUNDLED WITH
+   2.4.10
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..8b9a156
--- /dev/null
+++ b/README.md
@@ -0,0 +1,12 @@
+# SenseThing: A sensor tool for Linux
+
+`sensething` is a CLI tool that aims to:
+
+- Make as many sensors as possible visible from within a single tool,
+- Provide a human-friendly way of querying specific sensors,
+- Deliver output in formats that are easy to parse (for humans and computers),
+- Be as simple to use as possible.
+
+`sensething` provides access to all the same sensors as `lm-sensors`, but it
+also includes sensor data from Nvidia graphics cards, as well as CPU clock
+frequencies. It will provide access to even more sensors in the future.
diff --git a/Rakefile b/Rakefile
new file mode 100644
index 0000000..ecb65c7
--- /dev/null
+++ b/Rakefile
@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+require 'rubocop/rake_task'
+
+GEM_NAME = 'sensething'
+GEM_VERSION = '0.0.1'
+
+def del(pattern)
+  pattern = File.join(__dir__, pattern)
+  Dir.glob(pattern).each do |f|
+    File.delete f
+  end
+end
+
+task default: %i[build test]
+
+RuboCop::RakeTask.new(:lint) do |task|
+  task.patterns = ['lib/**/*.rb', 'test/**/*.rb']
+  task.fail_on_error = true
+end
+
+task :build do
+  system "gem build #{GEM_NAME} .gemspec"
+end
+
+task install: :build do
+  system "gem install #{GEM_NAME}-#{GEM_VERSION}.gem"
+end
+
+task publish: :build do
+  system "gem push #{GEM_NAME}-#{GEM_VERSION}.gem"
+end
+
+task :test do
+  Dir.glob('test/*.rb').each do |f|
+    ruby f
+  end
+end
+
+task :clean do
+  del '*.gem'
+end
diff --git a/bin/sensething b/bin/sensething
new file mode 100755
index 0000000..48a67e1
--- /dev/null
+++ b/bin/sensething
@@ -0,0 +1,126 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+require 'sensething'
+require 'csv'
+require 'json'
+
+def gather_sensors
+  result = {}
+  SenseThing.discover_devices do |dev|
+    dev.each_sensor do |sensor|
+      result[sensor.name] = sensor
+    end
+  end
+  result
+end
+
+def gather_relevant_sensors(names)
+  sensors = gather_sensors
+  names.map do |name|
+    s = sensors[name]
+    raise "No sensor with name '#{name}'" unless s
+
+    s
+  end
+end
+
+def putline
+  puts '=' * 80
+end
+
+def list_sensors
+  SenseThing.discover_devices do |dev|
+    dev.each_sensor do |sensor|
+      puts "#{sensor.name.to_s.ljust(29)} #{sensor.summary}"
+    end
+  end
+end
+
+def sensor_info(names)
+  names ||= []
+  sensors = gather_relevant_sensors(names)
+
+  sensors.each_with_index do |sensor, i|
+    puts "#{sensor.name.to_s.ljust(29)} #{sensor.summary}"
+    puts sensor.detail
+    putline if i < sensors.length - 1
+  end
+end
+
+def read_sensors(names)
+  names ||= []
+  sensors = gather_relevant_sensors(names)
+
+  sensors.each do |sensor|
+    # p sensor
+    puts "#{sensor.name.to_s.ljust(29)} #{sensor.fetch} #{sensor.unit}"
+  end
+end
+
+def log_csv(sensors, interval, units)
+  $stdout.sync = true
+  CSV($stdout.dup) do |csv|
+    csv << sensors.map do |s|
+      if units
+        "#{s.name} [#{s.unit}]"
+      else
+        s.name.to_s
+      end
+    end
+    loop do
+      csv << sensors.map(&:fetch)
+      sleep interval
+    end
+  end
+end
+
+def log_json(sensors, interval, units)
+  $stdout.sync = true
+  loop do
+    data = sensors.map do |s|
+      value = s.fetch
+      if units
+        [s.name.to_s, { value: value, unit: s.unit }]
+      else
+        [s.name.to_s, value]
+      end
+    end
+    data = data.to_h
+    JSON.dump(data, $stdout)
+    $stdout.write "\n"
+    sleep interval
+  end
+end
+
+def log_sensors(names, format, interval, units)
+  names ||= []
+  format ||= 'csv'
+  interval ||= 1
+  sensors = gather_relevant_sensors(names)
+
+  case format
+  when 'csv'
+    log_csv(sensors, interval, units)
+  when 'json'
+    log_json(sensors, interval, units)
+  else
+    raise "Invalid format: #{format}"
+  end
+end
+
+args = SenseThing::Cli.parse_command_line
+
+case args&.cmd&.name
+when nil
+  SenseThing::Cli.show_help
+  exit 0
+when 'list-sensors'
+  list_sensors
+when 'info'
+  sensor_info(args.cmd[:name])
+when 'read'
+  read_sensors(args.cmd[:name])
+when 'log'
+  log_sensors(args.cmd[:name], args.cmd[:format], args.cmd[:interval], args.cmd[:units])
+end
diff --git a/lib/sensething.rb b/lib/sensething.rb
new file mode 100644
index 0000000..3106389
--- /dev/null
+++ b/lib/sensething.rb
@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+require_relative 'sensething/sysfs'
+require_relative 'sensething/nvidia'
+require_relative 'sensething/cli'
+
+module SenseThing
+  def self.discover_devices(&block)
+    Dir.glob('/sys/class/hwmon/*').each do |path|
+      dev = begin
+        Sysfs::Hwmon.new(path)
+      rescue StandardError => e
+        warn "Tried to access a device at #{path.inspect}, but threw an exception: #{e}"
+        warn e.backtrace
+      end
+
+      yield dev
+    end
+
+    Dir.glob('/sys/devices/system/cpu/*/cpufreq') do |path|
+      dev = begin
+        Sysfs::Cpufreq.new(path)
+      rescue StandardError => e
+        warn "Tried to access a device at #{path.inspect}, but threw an exception: #{e}"
+        warn e.backtrace
+      end
+
+      yield dev
+    end
+
+    NvidiaSmi::SmiDevice.enumerate_gpus(&block)
+  end
+end
diff --git a/lib/sensething/cli.rb b/lib/sensething/cli.rb
new file mode 100644
index 0000000..776d0c7
--- /dev/null
+++ b/lib/sensething/cli.rb
@@ -0,0 +1,141 @@
+require 'optparse'
+
+module SenseThing
+  VERSION = Gem.loaded_specs['sensething']&.version
+
+  module Cli
+    class Command < OptionParser
+      attr_accessor :name, :short, :description
+      attr_reader :cmd
+
+      def initialize(name, &blk)
+        super(&blk)
+        @name = name
+        @flag_vals = {}
+        on('-h', '--help', 'Show help message and exit') do
+          full_help_message
+        end
+      end
+
+      def command(name, &block)
+        @commands ||= {}
+        opt = Command.new(name, &block)
+        banner_lead = banner.split(' - ', 2)[0]
+        opt.banner = "#{banner_lead} #{opt.name}"
+        opt.banner << " - #{opt.description}" if opt.description
+        @commands[opt.name.to_s] = opt
+        @commands[opt.short.to_s] = opt if opt.short
+      end
+
+      def order!(argv = ARGV, into: nil, &nonopt)
+        @cmd = match_cmd(argv)
+        if @cmd
+          argv.shift
+          @cmd.order!(argv, into: into, &nonopt)
+        else
+          super(argv, into: into, &nonopt)
+        end
+      end
+
+      def full_help_message
+        puts banner
+        if @commands
+          puts "\nCommands:"
+          cmds = Array(Set.new(@commands.values)).sort_by(&:name)
+          cmds.each do |c|
+            puts c.cmd_help
+          end
+        end
+        puts "\nOptions:"
+        puts summarize
+        exit 0
+      end
+
+      def [](k)
+        @flag_vals[k]
+      end
+
+      def []=(k, v)
+        @flag_vals[k] = v
+      end
+
+      protected
+
+      def cmd_help
+        result = "  #{name.rjust(12)} "
+        result << "   #{short} " if short
+        result = result.ljust(26)
+        width = 80 - result.length
+        desc = description.scan(/\S.{0,#{width}}\S(?=\s|$)|\S+/)
+        result << desc.shift
+        desc.each do |line|
+          result << "\n"
+          result << line.rjust(80)
+        end
+        result
+      end
+
+      private
+
+      def match_cmd(argv)
+        return unless @commands
+
+        @commands[argv[0]]
+      end
+    end
+
+    @option_parser = Command.new('sensething') do |parser| # rubocop:disable Metrics/BlockLength
+      parser.banner = 'sensething'
+      parser.command 'list-sensors' do |ls|
+        ls.description = 'List all available sensors'
+        ls.short = 'ls'
+      end
+      parser.command 'info' do |si|
+        si.description = 'Show detailed information about sensors'
+        si.short = 'i'
+        si.on '-s NAME', '--sensor NAME', 'Name of a sensor to show information about' do |n|
+          si[:name] = [] unless si[:name]
+          si[:name] << n
+        end
+      end
+      parser.command 'read' do |r|
+        r.description = 'Read sensor values'
+        r.short = 'r'
+        r.on '-s NAME', '--sensor NAME', 'Name of a sensor to read' do |n|
+          r[:name] = [] unless r[:name]
+          r[:name] << n
+        end
+      end
+      parser.command 'log' do |l|
+        l.description = 'Log sensor values continuously'
+        l.short = 'l'
+        l.on '-s NAME', '--sensor NAME', 'Name of a sensor to include in the logs' do |n|
+          l[:name] = [] unless l[:name]
+          l[:name] << n
+        end
+        l.on '-f FORMAT', '--format FORMAT', 'Output data format' do |f|
+          l[:format] = f
+        end
+        l.on '-i SECONDS', '--interval SECONDS', 'Data logging interval in seconds' do |i|
+          l[:interval] = Float(i)
+        end
+        l.on '-u', '--units', 'Include units in output data' do |_|
+          l[:units] = true
+        end
+      end
+      parser.on '-v', '--version', 'Show version info and exit' do
+        puts "Sensething #{VERSION}"
+        exit 0
+      end
+    end
+
+    def self.parse_command_line(argv = ARGV)
+      @option_parser.order!(argv)
+      @option_parser
+    end
+
+    def self.show_help
+      @option_parser.full_help_message
+    end
+  end
+end
diff --git a/lib/sensething/common/attribute.rb b/lib/sensething/common/attribute.rb
new file mode 100644
index 0000000..e62ac5b
--- /dev/null
+++ b/lib/sensething/common/attribute.rb
@@ -0,0 +1,31 @@
+# frozen_string_literal: true
+
+module SenseThing
+  class Attribute
+    def fetch
+      @val = read
+    end
+
+    def value(fetch: false)
+      return @val unless fetch || @val.nil?
+
+      self.fetch
+    end
+
+    def unit
+      nil
+    end
+
+    module DecimalNumber
+      def fetch
+        @val = Float(read)
+      end
+    end
+
+    module IntegralNumber
+      def fetch
+        @val = Integer(read)
+      end
+    end
+  end
+end
diff --git a/lib/sensething/common/device.rb b/lib/sensething/common/device.rb
new file mode 100644
index 0000000..9891a8d
--- /dev/null
+++ b/lib/sensething/common/device.rb
@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+module SenseThing
+  class Device
+    def each_attribute(&block)
+      return @attrs if @attrs
+
+      discover_attributes.each(&block)
+    end
+
+    def each_sensor
+      raise 'TODO'
+    end
+
+    def name
+      raise 'TODO'
+    end
+  end
+end
diff --git a/lib/sensething/nvidia.rb b/lib/sensething/nvidia.rb
new file mode 100644
index 0000000..f5b8e18
--- /dev/null
+++ b/lib/sensething/nvidia.rb
@@ -0,0 +1,3 @@
+# frozen_string_literal: true
+
+require_relative 'nvidia/smi'
diff --git a/lib/sensething/nvidia/attribute.rb b/lib/sensething/nvidia/attribute.rb
new file mode 100644
index 0000000..02f54e3
--- /dev/null
+++ b/lib/sensething/nvidia/attribute.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+require_relative '../common/attribute'
+
+module Nvidia
+  class Attribute < SenseThing::Attribute
+  end
+end
diff --git a/lib/sensething/nvidia/device.rb b/lib/sensething/nvidia/device.rb
new file mode 100644
index 0000000..e517a14
--- /dev/null
+++ b/lib/sensething/nvidia/device.rb
@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+require_relative '../common/device'
+
+module Nvidia
+  class Device < SenseThing::Device
+    attr_reader :name, :uuid
+
+    def initialize(name, uuid)
+      super()
+      @name = name
+      @uuid = uuid
+    end
+  end
+end
diff --git a/lib/sensething/nvidia/ffi.rb b/lib/sensething/nvidia/ffi.rb
new file mode 100644
index 0000000..3601aac
--- /dev/null
+++ b/lib/sensething/nvidia/ffi.rb
@@ -0,0 +1,135 @@
+# frozen_string_literal: true
+
+require 'mkmf'
+require 'fiddle'
+
+if have_library('nvidia-ml')
+  module Nvidia
+    module Ffi
+      extend Fiddle::Importer
+      dlload 'libnvidia-ml.so'
+    end
+  end
+end
+
+if $nvml_dll
+  module Nvidia
+    module Ffi
+      # The operation was successful.
+      NVML_SUCCESS = 0
+      # NVML was not first initialized with nvmlInit().
+      NVML_ERROR_UNINITIALIZED = 1
+      # A supplied argument is invalid.
+      NVML_ERROR_INVALID_ARGUMENT = 2
+      # The requested operation is not available on target device.
+      NVML_ERROR_NOT_SUPPORTED = 3
+      # The current user does not have permission for operation.
+      NVML_ERROR_NO_PERMISSION = 4
+      # Deprecated: Multiple initializations are now allowed through ref counting.
+      NVML_ERROR_ALREADY_INITIALIZED = 5
+      # A query to find an object was unsuccessful.
+      NVML_ERROR_NOT_FOUND = 6
+      # An input argument is not large enough.
+      NVML_ERROR_INSUFFICIENT_SIZE = 7
+      # A device's external power cables are not properly attached.
+      NVML_ERROR_INSUFFICIENT_POWER = 8
+      # NVIDIA driver is not loaded.
+      NVML_ERROR_DRIVER_NOT_LOADED = 9
+      # User provided timeout passed.
+      NVML_ERROR_TIMEOUT = 10
+      # NVIDIA Kernel detected an interrupt issue with a GPU.
+      NVML_ERROR_IRQ_ISSUE = 11
+      # NVML Shared Library couldn't be found or loaded.
+      NVML_ERROR_LIBRARY_NOT_FOUND = 12
+      # Local version of NVML doesn't implement this function.
+      NVML_ERROR_FUNCTION_NOT_FOUND = 13
+      # infoROM is corrupted
+      NVML_ERROR_CORRUPTED_INFOROM = 14
+      # The GPU has fallen off the bus or has otherwise become inaccessible.
+      NVML_ERROR_GPU_IS_LOST = 15
+      # The GPU requires a reset before it can be used again.
+      NVML_ERROR_RESET_REQUIRED = 16
+      # The GPU control device has been blocked by the operating system/cgroups.
+      NVML_ERROR_OPERATING_SYSTEM = 17
+      # RM detects a driver/library version mismatch.
+      NVML_ERROR_LIB_RM_VERSION_MISMATCH = 18
+      # An operation cannot be performed because the GPU is currently in use.
+      NVML_ERROR_IN_USE = 19
+      # Insufficient memory.
+      NVML_ERROR_MEMORY = 20
+      # No data.
+      NVML_ERROR_NO_DATA = 21
+      # The requested vgpu operation is not available on target device, becasue ECC is enabled.
+      NVML_ERROR_VGPU_ECC_NOT_SUPPORTED = 22
+      # Ran out of critical resources, other than memory.
+      NVML_ERROR_INSUFFICIENT_RESOURCES = 23
+      # Ran out of critical resources, other than memory.
+      NVML_ERROR_FREQ_NOT_SUPPORTED = 24
+      # The provided version is invalid/unsupported.
+      NVML_ERROR_ARGUMENT_VERSION_MISMATCH = 25
+      # The requested functionality has been deprecated.
+      NVML_ERROR_DEPRECATED = 26
+      # The system is not ready for the request.
+      NVML_ERROR_NOT_READY = 27
+      # An internal driver error occurred.
+      NVML_ERROR_UNKNOWN = 999
+
+      NVML_SYSTEM_NVML_VERSION_BUFFER_SIZE = 80
+      NVML_DEVICE_NAME_V2_BUFFER_SIZE = 96
+      NVML_DEVICE_SERIAL_BUFFER_SIZE = 30
+      NVML_DEVICE_UUID_V2_BUFFER_SIZE = 96
+
+      Fiddle.struct
+
+      INIT_WITH_FLAGS = Fiddle::Function.new(
+        $nvml_dll['nvmlInitWithFlags'],
+        [Fiddle::TYPE_UINT],
+        Fiddle::TYPE_INT
+      )
+
+      SHUT_DOWN = Fiddle::Function.new(
+        $nvml_dll['nvmlShutdown'],
+        [],
+        Fiddle::TYPE_INT
+      )
+
+      SYSTEM_GET_NVML_VERSION = Fiddle::Function.new(
+        $nvml_dll['nvmlSystemGetNVMLVersion'],
+        [Fiddle::TYPE_VOIDP, Fiddle::TYPE_UINT],
+        Fiddle::TYPE_INT
+      )
+
+      ERROR_STRING = Fiddle::Function.new(
+        $nvml_dll['nvmlErrorString'],
+        [Fiddle::TYPE_INT],
+        Fiddle::TYPE_VOIDP
+      )
+
+      GET_DEVICE_COUNT_V2 = Fiddle::Function.new(
+        $nvml_dll['nvmlDeviceGetCount_v2'],
+        [Fiddle::TYPE_UINTPTR_T],
+        Fiddle::TYPE_INT
+      )
+
+      GET_DEVICE_HANDLE_BY_INDEX_V2 = Fiddle::Function.new(
+        $nvml_dll['nvmlDeviceGetHandleByIndex_v2'],
+        [Fiddle::TYPE_UINT, Fiddle::TYPE_VOIDP],
+        Fiddle::TYPE_INT
+      )
+    end
+  end
+
+  if Nvidia::Ffi::INIT_WITH_FLAGS.call(1) == Nvidia::Ffi::NVML_SUCCESS
+    at_exit do
+      Nvidia::Ffi::SHUT_DOWN.call
+    end
+  else
+    $nvml_dll = nil
+  end
+end
+
+module Nvidia
+  def self.has_nvml?
+    !$nvml_dll.nil?
+  end
+end
diff --git a/lib/sensething/nvidia/smi.rb b/lib/sensething/nvidia/smi.rb
new file mode 100644
index 0000000..c75410c
--- /dev/null
+++ b/lib/sensething/nvidia/smi.rb
@@ -0,0 +1,489 @@
+# frozen_string_literal: true
+
+require_relative 'device'
+require_relative 'attribute'
+require 'open3'
+require 'csv'
+
+module NvidiaSmi
+  class SmiAttribute < Nvidia::Attribute
+    attr_accessor :type
+
+    def initialize(key, type, fetch_fn)
+      super()
+      @key = key.strip
+      @type = type
+      @fetch_fn = fetch_fn
+    end
+
+    def read
+      @fetch_fn.call[@key][0]
+    end
+
+    module Celsius
+      def unit
+        '°C'
+      end
+    end
+
+    module Rpm
+      include Nvidia::Attribute::DecimalNumber
+      def unit
+        'RPM'
+      end
+    end
+
+    module Megahertz
+      def fetch
+        raw = read
+        raise "Invalid nvidia-smi frequency string: #{raw.inspect}" unless /([0-9.]+) +MHz/ =~ raw
+
+        @val = Float($1)
+      end
+
+      def unit
+        'MHz'
+      end
+    end
+
+    module Watts
+      def fetch
+        raw = read
+        raise "Invalid nvidia-smi power string: #{raw.inspect}" unless /([0-9.]+) +W/ =~ raw
+
+        @val = Float($1)
+      end
+
+      def unit
+        'W'
+      end
+    end
+
+    module Percentage
+      def fetch
+        raw = read
+        raise "Invalid nvidia-smi percentage string: #{raw.inspect}" unless /([0-9.]+) +%/ =~ raw
+
+        @val = Float($1) / 100.0
+      end
+    end
+  end
+
+  class SmiDevice < Nvidia::Device
+    attr_reader :index
+
+    def initialize(name, uuid, index)
+      super(name, uuid)
+      @index = Integer(index)
+    end
+
+    def self.enumerate_gpus
+      Open3.popen3('nvidia-smi', '-L') do |i, o, _e, _t|
+        i.close
+        o.read.each_line do |line|
+          line.strip!
+          if /^GPU ([0-9]+): ([a-zA-Z0-9\- ]+) \(UUID: ([a-zA-Z0-9-]+)\)/ =~ line
+            yield SmiDevice.new($2, $3, $1)
+          end
+        end
+      end
+    end
+
+    def each_sensor # rubocop:disable Metrics/CyclomaticComplexity
+      remain = Array(each_attribute)
+      until remain.empty?
+        a0 = remain.shift
+        sens_attrs, remain = remain.partition { |a| a0.type == a.type }
+        sens_attrs << a0
+
+        case a0.type
+        when :temperature
+          yield NvidiaSmiTemperatureSensor.new(self, sens_attrs)
+        when :shader_clock
+          yield NvidiaSmiShaderFrequencySensor.new(self, sens_attrs)
+        when :mem_clock
+          yield NvidiaSmiMemoryFrequencySensor.new(self, sens_attrs)
+        when :video_clock
+          yield NvidiaSmiVideoFrequencySensor.new(self, sens_attrs)
+        when :pcie_gen
+          yield NvidiaSmiPcieLinkGenSensor.new(self, sens_attrs)
+        when :pcie_width
+          yield NvidiaSmiPcieLinkWidthSensor.new(self, sens_attrs)
+        when :power
+          yield NvidiaSmiPowerSensor.new(self, sens_attrs)
+        when :fan
+          yield NvidiaSmiFanSensor.new(self, sens_attrs)
+        end
+      end
+    end
+
+    private
+
+    def query_smi
+      Open3.popen3('nvidia-smi', "--id=#{@uuid}", "--query-gpu=#{@attr_keys.join(',')}",
+                   '--format=csv') do |i, o, _e, t|
+        i.close
+        return CSV.parse(o.read.strip, headers: true, strip: true) if t.value.success?
+      end
+      nil
+    end
+
+    def update_cached_smi_response
+      now = DateTime.now
+      return @cached_smi_response unless @last_update.nil? || (now - @last_update >= Rational(1, 86_401))
+
+      @last_update = now
+      @cached_smi_response = query_smi
+    end
+
+    protected
+
+    def discover_attributes # rubocop:disable Metrics/MethodLength
+      attrs = []
+      @attr_keys = []
+      fetch_fn = -> { update_cached_smi_response }
+      # Probe attributes individually to figure out which ones are available
+      discover_attribute('temperature.gpu') do |k|
+        attrs << TemperatureValue.new('temperature.gpu', :temperature, fetch_fn)
+        @attr_keys << k
+      end
+      discover_attribute('clocks.current.graphics') do |k|
+        attrs << ShaderFrequencyValue.new('clocks.current.graphics [MHz]', :shader_clock, fetch_fn)
+        @attr_keys << k
+      end
+      discover_attribute('clocks.max.graphics') do |k|
+        attrs << ShaderFrequencyMax.new('clocks.max.graphics [MHz]', :shader_clock, fetch_fn)
+        @attr_keys << k
+      end
+      discover_attribute('clocks.current.memory') do |k|
+        attrs << MemoryFrequencyValue.new('clocks.current.memory [MHz]', :mem_clock, fetch_fn)
+        @attr_keys << k
+      end
+      discover_attribute('clocks.max.memory') do |k|
+        attrs << MemoryFrequencyMax.new('clocks.max.memory [MHz]', :mem_clock, fetch_fn)
+        @attr_keys << k
+      end
+      discover_attribute('clocks.current.video') do |k|
+        attrs << VideoFrequencyValue.new('clocks.current.video [MHz]', :video_clock, fetch_fn)
+        @attr_keys << k
+      end
+      discover_attribute('clocks.max.video') do |k|
+        attrs << VideoFrequencyMax.new('clocks.max.video [MHz]', :video_clock, fetch_fn)
+        @attr_keys << k
+      end
+      discover_attribute('pcie.link.gen.gpucurrent') do |k|
+        attrs << PcieLinkGenValue.new('pcie.link.gen.gpucurrent', :pcie_gen, fetch_fn)
+        @attr_keys << k
+      end
+      discover_attribute('pcie.link.gen.max') do |k|
+        attrs << PcieLinkGenMax.new('pcie.link.gen.max', :pcie_gen, fetch_fn)
+        @attr_keys << k
+      end
+      discover_attribute('pcie.link.gen.gpumax') do |k|
+        attrs << PcieLinkGenSupportedByGpu.new('pcie.link.gen.gpumax', :pcie_gen, fetch_fn)
+        @attr_keys << k
+      end
+      discover_attribute('pcie.link.width.current') do |k|
+        attrs << PcieLinkWidthValue.new('pcie.link.width.current', :pcie_width, fetch_fn)
+        @attr_keys << k
+      end
+      discover_attribute('pcie.link.width.max') do |k|
+        attrs << PcieLinkWidthMax.new('pcie.link.width.max', :pcie_width, fetch_fn)
+        @attr_keys << k
+      end
+      discover_attribute('power.draw') do |k|
+        attrs << PowerValue.new('power.draw [W]', :power, fetch_fn)
+        @attr_keys << k
+      end
+      discover_attribute('power.limit') do |k|
+        attrs << PowerMax.new('power.limit [W]', :power, fetch_fn)
+        @attr_keys << k
+      end
+      discover_attribute('fan.speed') do |k|
+        attrs << FanSpeedValue.new('fan.speed [%]', :fan, fetch_fn)
+        @attr_keys << k
+      end
+      @attrs = attrs
+    end
+
+    private
+
+    def discover_attribute(key)
+      Open3.popen3('nvidia-smi', "--id=#{uuid}", "--query-gpu=#{key}", '--format=csv,noheader') do |i, _o, _e, t|
+        i.close
+        yield key if t.value.success?
+      end
+    end
+  end
+
+  class SmiSensor < SenseThing::Sensor
+    attr_reader :device, :value_attr, :min_attr, :max_attr
+
+    def initialize(device)
+      super()
+      @device = device
+    end
+
+    def unit
+      value_attr&.unit
+    end
+
+    def fetch
+      value_attr&.fetch
+    end
+
+    def value(fetch: false)
+      value_attr&.value(fetch: fetch)
+    end
+
+    def minimum
+      min_attr&.value
+    end
+
+    def maximum
+      max_attr&.value
+    end
+
+    def units
+      value_attr&.unit
+    end
+  end
+
+  class NvidiaSmiTemperatureSensor < SmiSensor
+    def initialize(device, attrs)
+      super(device)
+      attrs.each do |a|
+        case a
+        when TemperatureValue
+          @value_attr = a
+        end
+      end
+    end
+
+    def name
+      "nvidia#{device.index}/temperature"
+    end
+
+    def summary
+      "Temperature Sensor (nvidia#{device.index})"
+    end
+
+    def detail
+      result = []
+      result << "gpu: #{device.name}"
+      result << "gpuid: #{device.uuid}"
+    end
+  end
+
+  class NvidiaSmiShaderFrequencySensor < SmiSensor
+    def initialize(device, attrs)
+      super(device)
+      attrs.each do |a|
+        case a
+        when ShaderFrequencyValue
+          @value_attr = a
+        when ShaderFrequencyMax
+          @max_attr = a
+        end
+      end
+    end
+
+    def name
+      "nvidia#{device.index}/shader_frequency"
+    end
+
+    def summary
+      "Shader Frequency (nvidia#{device.index})"
+    end
+  end
+
+  class NvidiaSmiMemoryFrequencySensor < SmiSensor
+    def initialize(device, attrs)
+      super(device)
+      attrs.each do |a|
+        case a
+        when MemoryFrequencyValue
+          @value_attr = a
+        when MemoryFrequencyMax
+          @max_attr = a
+        end
+      end
+    end
+
+    def name
+      "nvidia#{device.index}/mem_frequency"
+    end
+
+    def summary
+      "Memory Frequency (nvidia#{device.index})"
+    end
+  end
+
+  class NvidiaSmiVideoFrequencySensor < SmiSensor
+    def initialize(device, attrs)
+      super(device)
+      attrs.each do |a|
+        case a
+        when VideoFrequencyValue
+          @value_attr = a
+        when VideoFrequencyMax
+          @max_attr = a
+        end
+      end
+    end
+
+    def name
+      "nvidia#{device.index}/video_frequency"
+    end
+
+    def summary
+      "Video Frequency (nvidia#{device.index})"
+    end
+  end
+
+  class NvidiaSmiPcieLinkGenSensor < SmiSensor
+    def initialize(device, attrs)
+      super(device)
+      attrs.each do |a|
+        case a
+        when PcieLinkGenValue
+          @value_attr = a
+        when PcieLinkGenMax
+          @max_attr = a
+        end
+      end
+    end
+
+    def name
+      "nvidia#{device.index}/pcie_gen"
+    end
+
+    def summary
+      "PCIe Link Generation (nvidia#{device.index})"
+    end
+  end
+
+  class NvidiaSmiPcieLinkWidthSensor < SmiSensor
+    def initialize(device, attrs)
+      super(device)
+      attrs.each do |a|
+        case a
+        when PcieLinkWidthValue
+          @value_attr = a
+        when PcieLinkWidthMax
+          @max_attr = a
+        end
+      end
+    end
+
+    def name
+      "nvidia#{device.index}/pcie_width"
+    end
+
+    def summary
+      "PCIe Link Width (nvidia#{device.index})"
+    end
+  end
+
+  class NvidiaSmiPowerSensor < SmiSensor
+    def initialize(device, attrs)
+      super(device)
+      attrs.each do |a|
+        case a
+        when PowerValue
+          @value_attr = a
+        when PowerMax
+          @max_attr = a
+        end
+      end
+    end
+
+    def name
+      "nvidia#{device.index}/power"
+    end
+
+    def summary
+      "Power Sensor (nvidia#{device.index})"
+    end
+  end
+
+  class NvidiaSmiFanSensor < SmiSensor
+    def initialize(device, attrs)
+      super(device)
+      attrs.each do |a|
+        case a
+        when FanSpeedValue
+          @value_attr = a
+        end
+      end
+    end
+
+    def name
+      "nvidia#{device.index}/fan"
+    end
+
+    def summary
+      "Fan (nvidia#{device.index})"
+    end
+  end
+
+  class TemperatureValue < SmiAttribute
+    include Celsius
+  end
+
+  class ShaderFrequencyValue < SmiAttribute
+    include Megahertz
+  end
+
+  class ShaderFrequencyMax < SmiAttribute
+    include Megahertz
+  end
+
+  class MemoryFrequencyValue < SmiAttribute
+    include Megahertz
+  end
+
+  class MemoryFrequencyMax < SmiAttribute
+    include Megahertz
+  end
+
+  class VideoFrequencyValue < SmiAttribute
+    include Megahertz
+  end
+
+  class VideoFrequencyMax < SmiAttribute
+    include Megahertz
+  end
+
+  class PcieLinkGenValue < SmiAttribute
+    include Nvidia::Attribute::IntegralNumber
+  end
+
+  class PcieLinkGenMax < SmiAttribute
+    include Nvidia::Attribute::IntegralNumber
+  end
+
+  class PcieLinkGenSupportedByGpu < SmiAttribute
+    include Nvidia::Attribute::IntegralNumber
+  end
+
+  class PcieLinkWidthValue < SmiAttribute
+    include Nvidia::Attribute::IntegralNumber
+  end
+
+  class PcieLinkWidthMax < SmiAttribute
+    include Nvidia::Attribute::IntegralNumber
+  end
+
+  class PowerValue < SmiAttribute
+    include Watts
+  end
+
+  class PowerMax < SmiAttribute
+    include Watts
+  end
+
+  class FanSpeedValue < SmiAttribute
+    include Percentage
+  end
+end
diff --git a/lib/sensething/sensor.rb b/lib/sensething/sensor.rb
new file mode 100644
index 0000000..fad07f5
--- /dev/null
+++ b/lib/sensething/sensor.rb
@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+module SenseThing
+  class Sensor
+    def name
+      raise 'TODO'
+    end
+
+    def fetch
+      raise 'TODO'
+    end
+
+    def value(fetch: false)
+      @value = self.fetch if fetch
+      @value
+    end
+
+    def minimum; end
+    def maximum; end
+
+    def limits
+      [minimum, maximum]
+    end
+
+    def summary
+      raise 'TODO'
+    end
+
+    def detail
+      raise 'TODO'
+    end
+
+    def unit
+      raise 'TODO'
+    end
+  end
+end
diff --git a/lib/sensething/sysfs.rb b/lib/sensething/sysfs.rb
new file mode 100644
index 0000000..ec132cb
--- /dev/null
+++ b/lib/sensething/sysfs.rb
@@ -0,0 +1,5 @@
+# frozen_string_literal: true
+
+require_relative 'sysfs/hwmon'
+require_relative 'sysfs/cpufreq'
+require_relative 'sysfs/drm'
diff --git a/lib/sensething/sysfs/attribute.rb b/lib/sensething/sysfs/attribute.rb
new file mode 100644
index 0000000..838a211
--- /dev/null
+++ b/lib/sensething/sysfs/attribute.rb
@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+
+require_relative '../common/attribute'
+require 'pathname'
+
+module Sysfs
+  class Attribute < SenseThing::Attribute
+    attr_reader :path
+
+    def initialize(path)
+      super()
+      @path = path
+      @path = Pathname.new(@path) unless @path.instance_of? Pathname
+      @path = @path.realpath
+      return if @path.file?
+
+      raise "Not a file: #{@path.inspect}"
+    end
+
+    def read
+      File.read(path)
+    end
+
+    def same_sensor?(_other)
+      raise 'TODO'
+    end
+  end
+end
diff --git a/lib/sensething/sysfs/cpufreq.rb b/lib/sensething/sysfs/cpufreq.rb
new file mode 100644
index 0000000..d15b233
--- /dev/null
+++ b/lib/sensething/sysfs/cpufreq.rb
@@ -0,0 +1,142 @@
+# frozen_string_literal: true
+
+require 'pathname'
+require_relative 'attribute'
+require_relative 'device'
+
+module Sysfs
+  class CpufreqAttribute < Attribute
+    module Megahertz
+      def fetch
+        # hwmon measures in kilohertz
+        @val = Float(read) / 1000.0
+      end
+
+      def unit
+        'MHz'
+      end
+
+      def same_sensor?(_other)
+        true # for cpufreq, each 'device' represents a single sensor
+      end
+    end
+  end
+
+  class Cpufreq < Device
+    def self.parse_attr_by_name(name, path)
+      case name
+      when 'scaling_cur_freq'
+        FrequencyValue.new(path)
+      when 'scaling_min_freq'
+        FrequencyMin.new(path)
+      when 'scaling_max_freq'
+        FrequencyMax.new(path)
+      when 'scaling_governor'
+        Governor.new(path)
+      end
+    end
+
+    def create_sensor(attrs)
+      CpuFreqSensor.new(self, attrs)
+    end
+
+    protected
+
+    def discover_attributes
+      attrs = []
+      @path.each_child do |pn|
+        if (attr = self.class.parse_attr_by_name(pn.basename.to_s, pn))
+          attrs << attr
+        end
+      end
+      @attrs = attrs
+    end
+
+    def discover_name
+      related_cpus = File.read(@path.join('related_cpus')).strip
+      @name = "cpu#{related_cpus.split(' ').join('_')}"
+    rescue Errno::ENOENT
+      @noname = true
+    end
+  end
+
+  class CpuFreqSensor < SenseThing::Sensor
+    attr_reader :device, :min_attr, :max_attr, :value_attr, :governor_attr
+
+    def initialize(device, attrs)
+      super()
+      @device = device
+      attrs.each do |a|
+        case a
+        when FrequencyMin
+          @min_attr = a
+        when FrequencyMax
+          @max_attr = a
+        when FrequencyValue
+          @value_attr = a
+        when Governor
+          @governor_attr = a
+        end
+      end
+    end
+
+    def unit
+      value_attr&.unit
+    end
+
+    def fetch
+      value_attr&.fetch
+    end
+
+    def value(fetch: false)
+      value_attr&.value(fetch: fetch)
+    end
+
+    def minimum
+      min_attr&.value
+    end
+
+    def maximum
+      max_attr&.value
+    end
+
+    def units
+      value_attr&.unit
+    end
+
+    def name
+      "#{device.name}/frequency"
+    end
+
+    def summary
+      "CPU Frequency (cpufreq/#{device.path.basename})"
+    end
+
+    def detail
+      result = []
+      result << "value: #{value_attr.path}" if value_attr
+      result << "governor: #{governor_attr.path}" if governor_attr
+      result << "min: #{min_attr.path}" if min_attr
+      result << "max: #{max_attr.path}" if max_attr
+      result.join("\n")
+    end
+  end
+
+  class FrequencyValue < CpufreqAttribute
+    include Megahertz
+  end
+
+  class FrequencyMin < CpufreqAttribute
+    include Megahertz
+  end
+
+  class FrequencyMax < CpufreqAttribute
+    include Megahertz
+  end
+
+  class Governor < CpufreqAttribute
+    def fetch
+      @val = read.strip
+    end
+  end
+end
diff --git a/lib/sensething/sysfs/device.rb b/lib/sensething/sysfs/device.rb
new file mode 100644
index 0000000..a478101
--- /dev/null
+++ b/lib/sensething/sysfs/device.rb
@@ -0,0 +1,52 @@
+# frozen_string_literal: true
+
+require_relative '../common/device'
+require 'pathname'
+
+module Sysfs
+  class Device < SenseThing::Device
+    attr_reader :path
+
+    def initialize(path)
+      super()
+      @path = path
+      @path = Pathname.new(@path) unless @path.instance_of? Pathname
+      @path = @path.realpath
+      raise "Not a directory: #{@path.inspect}" unless @path.directory?
+
+      @attrs = nil
+      @name = nil
+      @noname = false
+    end
+
+    def name
+      return @name if @name || @noname
+
+      discover_name
+    end
+
+    def each_attribute(&block)
+      return @attrs if @attrs
+
+      discover_attributes.each(&block)
+    end
+
+    def each_sensor
+      remain = Array(each_attribute)
+      until remain.empty?
+        a0 = remain.shift
+        sens_attrs, remain = remain.partition { |a| a0.same_sensor? a }
+        sens_attrs << a0
+        yield create_sensor(sens_attrs)
+      end
+    end
+
+    def discover_attributes
+      raise 'TODO'
+    end
+
+    def create_sensor(_attrs)
+      raise 'TODO'
+    end
+  end
+end
diff --git a/lib/sensething/sysfs/drm.rb b/lib/sensething/sysfs/drm.rb
new file mode 100644
index 0000000..33494b7
--- /dev/null
+++ b/lib/sensething/sysfs/drm.rb
@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+require 'pathname'
+require_relative 'attribute'
+require_relative 'device'
+
+# TODO
+module Sysfs
+end
diff --git a/lib/sensething/sysfs/hwmon.rb b/lib/sensething/sysfs/hwmon.rb
new file mode 100644
index 0000000..cc69377
--- /dev/null
+++ b/lib/sensething/sysfs/hwmon.rb
@@ -0,0 +1,702 @@
+# frozen_string_literal: true
+
+require 'pathname'
+require_relative '../sensor'
+require_relative 'attribute'
+require_relative 'device'
+
+module Sysfs
+  class HwmonAttribute < Attribute
+    attr_reader :chan_num
+
+    def initialize(path, chan_num)
+      super(path)
+      @chan_num = Integer(chan_num)
+    end
+
+    def type
+      raise 'TODO'
+    end
+
+    def same_sensor?(other)
+      chan_num == other.chan_num && type == other.type
+    end
+
+    module Millivolts
+      include Attribute::DecimalNumber
+      def unit
+        'mV'
+      end
+
+      def type
+        :voltage
+      end
+    end
+
+    module Milliamps
+      include Attribute::DecimalNumber
+      def unit
+        'mA'
+      end
+
+      def type
+        :current
+      end
+    end
+
+    module Rpm
+      include Attribute::DecimalNumber
+      def unit
+        'RPM'
+      end
+
+      def type
+        :fan
+      end
+    end
+
+    module Celsius
+      def fetch
+        # hwmon measures in millidegrees
+        @val = Float(read) / 1000.0
+      end
+
+      def unit
+        '°C'
+      end
+
+      def type
+        :temperature
+      end
+    end
+  end
+
+  class Hwmon < Device
+    def self.parse_attr_by_name(name, path)
+      if name.start_with? 'in'
+        chan_num, type = parse_attr_num_text(name[2..])
+        parse_in_attr(chan_num, type, path)
+      elsif name.start_with? 'curr'
+        chan_num, type = parse_attr_num_text(name[4..])
+        parse_curr_attr(chan_num, type, path)
+      elsif name.start_with? 'fan'
+        chan_num, type = parse_attr_num_text(name[3..])
+        parse_fan_attr(chan_num, type, path)
+      elsif name.start_with? 'pwm'
+        chan_num, type = parse_attr_num_text(name[3..])
+        parse_pwm_attr(chan_num, type, path)
+      elsif name.start_with? 'temp'
+        chan_num, type = parse_attr_num_text(name[4..])
+        parse_temperature_attr(chan_num, type, path)
+      end
+    end
+
+    def create_sensor(attrs)
+      case attrs[0].type
+      when :voltage
+        HwmonVoltageSensor.new(self, attrs[0].type, attrs[0].chan_num, attrs)
+      when :current
+        HwmonCurrentSensor.new(self, attrs[0].type, attrs[0].chan_num, attrs)
+      when :temperature
+        HwmonTemperatureSensor.new(self, attrs[0].type, attrs[0].chan_num, attrs)
+      when :fan
+        HwmonFanSensor.new(self, attrs[0].type, attrs[0].chan_num, attrs)
+      when :pwm
+        HwmonPwmSensor.new(self, attrs[0].type, attrs[0].chan_num, attrs)
+      end
+    end
+
+    protected
+
+    def discover_attributes
+      attrs = []
+      @path.each_child do |pn|
+        if (attr = self.class.parse_attr_by_name(pn.basename.to_s, pn))
+          attrs << attr
+        end
+      end
+      @attrs = attrs.sort_by { |a| [a.chan_num, a.path.basename.to_s] }
+    end
+
+    def discover_name
+      @name = File.read(@path.join('name')).strip
+    rescue Errno::ENOENT
+      @noname = true
+    end
+
+    class << self
+      def parse_in_attr(chan_num, type, path)
+        case type
+        when 'min'
+          VoltageMin.new(path, chan_num)
+        when 'lcrit'
+          VoltageCriticalMin.new(path, chan_num)
+        when 'max'
+          VoltageMax.new(path, chan_num)
+        when 'crit'
+          VoltageCriticalMax.new(path, chan_num)
+        when 'input'
+          VoltageValue.new(path, chan_num)
+        when 'average'
+          VoltageAverage.new(path, chan_num)
+        when 'lowest'
+          VoltageLowest.new(path, chan_num)
+        when 'highest'
+          VoltageHighest.new(path, chan_num)
+        when 'label'
+          VoltageLabel.new(path, chan_num)
+        end
+      end
+
+      def parse_curr_attr(chan_num, type, path)
+        case type
+        when 'min'
+          CurrentMin.new(path, chan_num)
+        when 'lcrit'
+          CurrentCriticalMin.new(path, chan_num)
+        when 'max'
+          CurrentMax.new(path, chan_num)
+        when 'crit'
+          CurrentCriticalMax.new(path, chan_num)
+        when 'input'
+          CurrentValue.new(path, chan_num)
+        when 'average'
+          CurrentAverage.new(path, chan_num)
+        when 'lowest'
+          CurrentLowest.new(path, chan_num)
+        when 'highest'
+          CurrentHighest.new(path, chan_num)
+        end
+      end
+
+      def parse_fan_attr(chan_num, type, path)
+        case type
+        when 'min'
+          FanMin.new(path, chan_num)
+        when 'max'
+          FanMax.new(path, chan_num)
+        when 'input'
+          FanValue.new(path, chan_num)
+        when 'div'
+          FanDivisor.new(path, chan_num)
+        when 'pulses'
+          FanPulses.new(path, chan_num)
+        when 'target'
+          FanTarget.new(path, chan_num)
+        when 'label'
+          FanLabel.new(path, chan_num)
+        when 'enable'
+          FanEnabled.new(path, chan_num)
+        end
+      end
+
+      def parse_pwm_attr(chan_num, type, path)
+        case type
+        when nil
+          PwmValue.new(path, chan_num) if chan_num
+        when 'enable'
+          PwmEnabled.new(path, chan_num)
+        end
+      end
+
+      def parse_temperature_attr(chan_num, type, path) # rubocop:disable Metrics/MethodLength,Metrics/CyclomaticComplexity
+        case type
+        when 'type'
+          TemperatureType.new(path, chan_num)
+        when 'max'
+          TemperatureMax.new(path, chan_num)
+        when 'min'
+          TemperatureMin.new(path, chan_num)
+        when 'max_hyst'
+          TemperatureMaxHysteresis.new(path, chan_num)
+        when 'min_hyst'
+          TemperatureMinHysteresis.new(path, chan_num)
+        when 'input'
+          TemperatureValue.new(path, chan_num)
+        when 'crit'
+          TemperatureCriticalMax.new(path, chan_num)
+        when 'crit_hyst'
+          TemperatureCriticalMaxHysteresis.new(path, chan_num)
+        when 'lcrit'
+          TemperatureCriticalMin.new(path, chan_num)
+        when 'lcrit_hyst'
+          TemperatureCriticalMinHysteresis.new(path, chan_num)
+        when 'emergency'
+          TemperatureEmergency.new(path, chan_num)
+        when 'emergency_hyst'
+          TemperatureEmergencyHysteresis.new(path, chan_num)
+        when 'lowest'
+          TemperatureLowest.new(path, chan_num)
+        when 'highest'
+          TemperatureHighest.new(path, chan_num)
+        when 'label'
+          TemperatureLabel.new(path, chan_num)
+        when 'enable'
+          TemperatureEnable.new(path, chan_num)
+        end
+      end
+
+      def parse_attr_num_text(subname)
+        return unless /^([0-9]+)/ =~ subname
+
+        num = $1
+        return [num] if num.length == subname.length
+
+        subname = subname[num.length..]
+
+        return unless /^_([a-z_]+)$/ =~ subname
+
+        [num, $1]
+      end
+    end
+  end
+
+  class HwmonSensor < SenseThing::Sensor
+    attr_reader :device, :label_attr, :value_attr, :min_attr, :max_attr
+
+    def initialize(device, type, chan_num)
+      super()
+      @device = device
+      @type = type
+      @chan_num = chan_num
+    end
+
+    def name
+      if label_attr
+        "#{device.name}/#{label_attr.value}"
+      else
+        "#{device.name}/#{@type}_#{@chan_num}"
+      end
+    end
+
+    def unit
+      value_attr&.unit
+    end
+
+    def fetch
+      value_attr&.fetch
+    end
+
+    def value(fetch: false)
+      value_attr&.value(fetch: fetch)
+    end
+
+    def minimum
+      min_attr&.value
+    end
+
+    def maximum
+      max_attr&.value
+    end
+
+    def units
+      value_attr&.unit
+    end
+  end
+
+  class HwmonVoltageSensor < HwmonSensor
+    def initialize(device, type, chan_num, attrs)
+      super(device, type, chan_num)
+      attrs.each do |a|
+        case a
+        when VoltageMin
+          @min_attr = a
+        when VoltageMax
+          @max_attr = a
+        when VoltageCriticalMin
+          @crit_min_attr = a
+        when VoltageCriticalMax
+          @crit_max_attr = a
+        when VoltageValue
+          @value_attr = a
+        when VoltageLabel
+          @label_attr = a
+        end
+      end
+    end
+
+    def summary
+      "Voltage Sensor (#{device.path.basename}/in#{@chan_num})"
+    end
+
+    def detail
+      result = []
+      result << "value: #{value_attr.path}" if value_attr
+      result << "label: #{label_attr.path}" if label_attr
+      result << "min: #{min_attr.path}" if min_attr
+      result << "max: #{max_attr.path}" if max_attr
+      result << "critical min: #{crit_min_attr.path}" if @crit_min_attr
+      result << "critical max: #{crit_max_attr.path}" if @crit_max_attr
+      result.join("\n")
+    end
+  end
+
+  class HwmonCurrentSensor < HwmonSensor
+    def initialize(device, type, chan_num, attrs)
+      super(device, type, chan_num)
+      attrs.each do |a|
+        case a
+        when CurrentMin
+          @min_attr = a
+        when CurrentMax
+          @max_attr = a
+        when CurrentCriticalMin
+          @crit_min_attr = a
+        when CurrentCriticalMax
+          @crit_max_attr = a
+        when CurrentValue
+          @value_attr = a
+        when CurrentLabel
+          @label_attr = a
+        end
+      end
+    end
+
+    def summary
+      "Current Sensor (#{device.path.basename}/curr#{@chan_num})"
+    end
+
+    def detail
+      result = []
+      result << "value: #{value_attr.path}" if value_attr
+      result << "label: #{label_attr.path}" if label_attr
+      result << "min: #{min_attr.path}" if min_attr
+      result << "max: #{max_attr.path}" if max_attr
+      result << "critical min: #{crit_min_attr.path}" if @crit_min_attr
+      result << "critical max: #{crit_max_attr.path}" if @crit_max_attr
+      result.join("\n")
+    end
+  end
+
+  class HwmonTemperatureSensor < HwmonSensor
+    def initialize(device, type, chan_num, attrs)
+      super(device, type, chan_num)
+      attrs.each do |a|
+        case a
+        when TemperatureMin
+          @min_attr = a
+        when TemperatureMax
+          @max_attr = a
+        when TemperatureValue
+          @value_attr = a
+        when TemperatureLabel
+          @label_attr = a
+        when TemperatureType
+          @temp_type_attr = a
+        end
+      end
+    end
+
+    def summary
+      "Temperature Sensor (#{device.path.basename}/temp#{@chan_num})"
+    end
+
+    def detail
+      result = []
+      result << "value: #{value_attr.path}" if value_attr
+      result << "label: #{label_attr.path}" if label_attr
+      result << "min: #{min_attr.path}" if min_attr
+      result << "max: #{max_attr.path}" if max_attr
+      result << "type: #{@temp_type_attr.path}" if @temp_type_attr
+      result.join("\n")
+    end
+  end
+
+  class HwmonFanSensor < HwmonSensor
+    def initialize(device, type, chan_num, attrs)
+      super(device, type, chan_num)
+      attrs.each do |a|
+        case a
+        when FanMin
+          @min_attr = a
+        when FanMax
+          @max_attr = a
+        when FanValue
+          @value_attr = a
+        when FanLabel
+          @label_attr = a
+        end
+      end
+    end
+
+    def summary
+      "Fan (#{device.path.basename}/fan#{@chan_num})"
+    end
+
+    def detail
+      result = []
+      result << "value: #{value_attr.path}" if value_attr
+      result << "label: #{label_attr.path}" if label_attr
+      result << "min: #{min_attr.path}" if min_attr
+      result << "max: #{max_attr.path}" if max_attr
+      result.join("\n")
+    end
+  end
+
+  class HwmonPwmSensor < HwmonSensor
+    def initialize(device, type, chan_num, attrs)
+      super(device, type, chan_num)
+      attrs.each do |a|
+        case a
+        when PwmValue
+          @value_attr = a
+        end
+      end
+    end
+
+    def summary
+      "PWM (#{device.path.basename}/pwm#{@chan_num})"
+    end
+
+    def detail
+      result = []
+      result << "value: #{value_attr.path}" if value_attr
+      result.join("\n")
+    end
+  end
+
+  class VoltageMin < HwmonAttribute
+    include Millivolts
+  end
+
+  class VoltageCriticalMin < HwmonAttribute
+    include Millivolts
+  end
+
+  class VoltageMax < HwmonAttribute
+    include Millivolts
+  end
+
+  class VoltageCriticalMax < HwmonAttribute
+    include Millivolts
+  end
+
+  class VoltageValue < HwmonAttribute
+    include Millivolts
+  end
+
+  class VoltageAverage < HwmonAttribute
+    include Millivolts
+  end
+
+  class VoltageLowest < HwmonAttribute
+    include Millivolts
+  end
+
+  class VoltageHighest < HwmonAttribute
+    include Millivolts
+  end
+
+  class VoltageLabel < HwmonAttribute
+    def fetch
+      @val = read.strip.gsub(/\s+/, '_')
+    end
+
+    def type
+      :voltage
+    end
+  end
+
+  class CurrentMin < HwmonAttribute
+    include Milliamps
+  end
+
+  class CurrentCriticalMin < HwmonAttribute
+    include Milliamps
+  end
+
+  class CurrentMax < HwmonAttribute
+    include Milliamps
+  end
+
+  class CurrentCriticalMax < HwmonAttribute
+    include Milliamps
+  end
+
+  class CurrentValue < HwmonAttribute
+    include Milliamps
+  end
+
+  class CurrentAverage < HwmonAttribute
+    include Milliamps
+  end
+
+  class CurrentLowest < HwmonAttribute
+    include Milliamps
+  end
+
+  class CurrentHighest < HwmonAttribute
+    include Milliamps
+  end
+
+  class FanMin < HwmonAttribute
+    include Rpm
+  end
+
+  class FanMax < HwmonAttribute
+    include Rpm
+  end
+
+  class FanValue < HwmonAttribute
+    include Rpm
+  end
+
+  class FanDivisor < HwmonAttribute
+    include IntegralNumber
+    def type
+      :fan
+    end
+  end
+
+  class FanPulses < HwmonAttribute
+    include IntegralNumber
+    def type
+      :fan
+    end
+  end
+
+  class FanTarget < HwmonAttribute
+    include Rpm
+    def type
+      :fan
+    end
+  end
+
+  class FanLabel < HwmonAttribute
+    def fetch
+      @val = read.strip
+    end
+
+    def type
+      :fan
+    end
+  end
+
+  class FanEnabled < HwmonAttribute
+    def fetch
+      @val = read.strip != '0'
+    end
+
+    def type
+      :fan
+    end
+  end
+
+  class PwmValue < HwmonAttribute
+    def fetch
+      @val = Float(read) / 255.0
+    end
+
+    def type
+      :pwm
+    end
+  end
+
+  class PwmEnabled < HwmonAttribute
+    def fetch
+      @val = read.strip != '0'
+    end
+
+    def type
+      :pwm
+    end
+  end
+
+  class TemperatureType < HwmonAttribute
+    CPU_DIODE = 1
+    TRANSISTOR_3904 = 2
+    THERMAL_DIODE = 3
+    THERMISTOR = 4
+    AMDSI = 5
+    PECI = 6
+
+    @type_vals = {
+      '1': CPU_DIODE,
+      '2': TRANSISTOR_3904,
+      '3': THERMAL_DIODE,
+      '4': THERMISTOR,
+      '5': AMDSI,
+      '6': PECI
+    }
+
+    def fetch
+      self.class.type_vals[read.strip]
+    end
+
+    def type
+      :temperature
+    end
+  end
+
+  class TemperatureMax < HwmonAttribute
+    include Celsius
+  end
+
+  class TemperatureMin < HwmonAttribute
+    include Celsius
+  end
+
+  class TemperatureMaxHysteresis < HwmonAttribute
+    include Celsius
+  end
+
+  class TemperatureMinHysteresis < HwmonAttribute
+    include Celsius
+  end
+
+  class TemperatureValue < HwmonAttribute
+    include Celsius
+  end
+
+  class TemperatureCriticalMax < HwmonAttribute
+    include Celsius
+  end
+
+  class TemperatureCriticalMaxHysteresis < HwmonAttribute
+    include Celsius
+  end
+
+  class TemperatureCriticalMin < HwmonAttribute
+    include Celsius
+  end
+
+  class TemperatureCriticalMinHysteresis < HwmonAttribute
+    include Celsius
+  end
+
+  class TemperatureEmergency < HwmonAttribute
+    include Celsius
+  end
+
+  class TemperatureEmergencyHysteresis < HwmonAttribute
+    include Celsius
+  end
+
+  class TemperatureLowest < HwmonAttribute
+    include Celsius
+  end
+
+  class TemperatureHighest < HwmonAttribute
+    include Celsius
+  end
+
+  class TemperatureLabel < HwmonAttribute
+    def fetch
+      @val = read.strip
+    end
+
+    def type
+      :temperature
+    end
+  end
+
+  class TemperatureEnable < HwmonAttribute
+    def fetch
+      @val = read.strip != '0'
+    end
+
+    def type
+      :temperature
+    end
+  end
+end
diff --git a/sensething.gemspec b/sensething.gemspec
new file mode 100644
index 0000000..43899ac
--- /dev/null
+++ b/sensething.gemspec
@@ -0,0 +1,14 @@
+Gem::Specification.new do |s|
+  s.name      = 'sensething'
+  s.version   = '0.0.1'
+  s.platform  = Gem::Platform::RUBY
+  s.summary   = 'Powerful sensor logging utility for Linux'
+  s.description = 'System-wide sensor data logging system with support for hwmon and nvidia-smi.'
+  s.authors   = ['Evan Perry Grove']
+  s.email     = ['evan@4grove.com']
+  s.homepage  = 'https://hardfault.life'
+  s.license   = 'GPL-3.0-only'
+  s.files     = Dir.glob("{lib,bin}/**/*") # This includes all files under the lib directory recursively, so we don't have to add each one individually.
+  s.require_path = 'lib'
+  s.executables = ['sensething']
+end
diff --git a/test/sanity_test.rb b/test/sanity_test.rb
new file mode 100644
index 0000000..21c658f
--- /dev/null
+++ b/test/sanity_test.rb
@@ -0,0 +1,10 @@
+# frozen_string_literal: true
+
+require 'minitest/autorun'
+require_relative '../lib/sensething'
+
+class SanityTest < Minitest::Test
+  def test_sanity
+    assert true
+  end
+end