dlux - hardware brightness control

dlux (pronunced like "deluxe") is a tiny hardware brightness control daemon that automatically sets hardware display brightness based on the time of day.

dlux requires a monitor that supports ddc/ci. Unlike f.lux or redshift, dlux:

• has zero performance impact with a tiny memory footprint
• reduces electricity use
• works with any Linux setup, even without a graphical session

Requirements

dlux requires userspace access to i2c devices through the i2c-dev module. This module must be loaded prior to launching dlux.

Additionally, your displays must support i2c brightness control (capability 0x10). You may preemptively check display capabilities through ddcutil. For example:

$ sudo ddcutil detect
Display 1
   I2C bus:             /dev/i2c-1
   EDID synopsis:
      Mfg id:           DEL
      Model:            DELL U2415
      Serial number:    DEADBEEF1744
      Manufacture year: 2019
      EDID version:     1.4
   VCP version:         2.1

Display 2
   I2C bus:             /dev/i2c-3
   EDID synopsis:
      Mfg id:           DEL
      Model:            DELL U2415
      Serial number:    JKLHF1200919
      Manufacture year: 2019
      EDID version:     1.4
   VCP version:         2.1

Display 3
   I2C bus:             /dev/i2c-6
   EDID synopsis:
      Mfg id:           DEL
      Model:            DELL U2720Q
      Serial number:    ABCD1234
      Manufacture year: 2020
      EDID version:     1.3
   VCP version:         2.1

$ sudo ddcutil getvcp 0x10 --bus 1 # from /dev/i2c-1
VCP code 0x10 (Brightness): current value = 100, max value = 100

$ sudo ddcutil getvcp 0x10 --bus 3 # /dev/i2c-3
VCP code 0x10 (Brightness): current value = 100, max value = 100

$ sudo ddcutil getvcp 0x10 --bus 6 # /dev/i2c-6
VCP code 0x10 (Brightness): current value = 100, max value = 100

Usage

dlux has three subcommands: probe, daemon, and run. run and daemon are functionally identically except daemon takes a config file and run uses entirely CLI parameters.

$ dlux --help
dlux 0.1.2
Dynamic hardware monitor brightness adjustment

USAGE:
    dlux <SUBCOMMAND>

FLAGS:
    -h, --help       Prints help information
    -V, --version    Prints version information

SUBCOMMANDS:
    daemon
    help      Prints this message or the help of the given subcommand(s)
    probe
    start

Daemon

The daemon takes a yaml configuration file as the first and only parameter:

$ dlux daemon --help
dlux-daemon 0.1.2

USAGE:
    dlux daemon <config>

FLAGS:
    -h, --help       Prints help information
    -V, --version    Prints version information

ARGS:
    <config>

$ dlux daemon config.yaml
[2020-12-19T22:33:01Z INFO  dlux::daemon] discovered 3 monitors
[2020-12-19T22:33:01Z INFO  dlux::daemon] updating brightness of all displays to nighttime value
[2020-12-19T22:33:01Z DEBUG lib::device] set brightness for /dev/i2c-1 to 40% (absolute 40)
[2020-12-19T22:33:01Z DEBUG lib::device] set brightness for /dev/i2c-3 to 40% (absolute 40)
[2020-12-19T22:33:01Z DEBUG lib::device] set brightness for /dev/i2c-5 to 40% (absolute 40)
[2020-12-19T22:33:01Z DEBUG dlux::daemon] finished setting monitor brightness
[2020-12-19T22:33:01Z INFO  dlux::daemon] sleeping for 1h 50m 55s until 2020-12-19 16:23:57.100 -08:00

Minimal configuration which manages all compatible devices automatically:

geo:
  latitude: 20
  longitude: -100
day_brightness: 100
night_brightness: 40

Configuration file with explicit device matches and per-device overrides of global settings. Note that all devices must be matched by the list.

geo:
  latitude: 20
  longitude: -100
  altitude: 200
logging:
  level: Debug
day_brightness: 100
night_brightness: 40
devices:
  - model: (?i)dell U2145
    day_brightness: 80
    night_brightness: 50
    manufacturer_id: DEL
  - model: DELL U2145

Configuration file with explicit device matches and per-device overrides of global settings. By default, devices matched are overriden but all devices are managed, but device_match_exclusive can make it so only matched devices are handled.

geo:
  latitude: 20
  longitude: -100
day_brightness: 100
night_brightness: 40
device_match_exclusive: true
devices:
  - model: (?i)dell U2145
  - model: DELL U2145

Legacy CLI

dlux start mirrors classic CLI usage. It will run a daemon indefinitely based on passed parameters. It does not accept a config file.

$ dlux start
dlux-start 0.1.2

USAGE:
    dlux start [OPTIONS] --latitude <latitude> --longitude <longitude>

FLAGS:
    -h, --help       Prints help information
    -V, --version    Prints version information

OPTIONS:
        --altitude <altitude>
            altitude from sea level in meters of your location for sunset calculations [default: 0.0]

    -d, --day-brightness <day-brightness>        percentage of the target screen brightness during day
        --latitude <latitude>                    latitude of your location for sunset calculations
        --log-level <level>
            minimum log level printed to STDERR. Choose from: trace, debug, info, warn, error, off [default: info]

        --longitude <longitude>                  longitude of your location for sunset calculations
    -n, --night-brightness <night-brightness>    percentage of the target screen brightness after sunset
        --log-style <style>
            controls when log output is colored. Choose from: auto, always, and never [default: Auto]

After compiling, provide your latitude, longitude, and desired nighttime brightness:

$ dlux --day-brightness 100 --night-brightness 40 --latitude 40 --longitude="-120"
[2020-12-19T22:27:51Z INFO  dlux::daemon] discovered 3 monitors
[2020-12-19T22:27:51Z INFO  dlux::daemon] updating brightness of all displays to daytime value
[2020-12-19T22:27:52Z INFO  dlux::daemon] sleeping for 18h 21m 29s until 2020-12-20 08:49:21.100 -08:00

Probe

dlux probe provides valid config yaml for all the currently available supported devices:

$ dlux probe
---
devices:
  - model: PA278CV
    manufacturer_id: AUS
    serial: M3LMQS362198
  - model: DELL U2720Q
    manufacturer_id: DEL
    serial: F8KFX13
  - model: ASUS PB277
    manufacturer_id: ACI
    serial: ""