Provided by: ddcutil_0.9.8-2_amd64 bug


       ddcutil - Query and change monitor settings


       ddcutil   [--adl|-a   adapter-index.display-index]   [--async]  [--bus|-b  busno]  [--ddc]
       [--display|--dis|-d  dispno]  [--edid  256  hex  character  EDID]  [--excp]   [-f|--force]
       [--force-slave-address]   [--hiddev   hiddevdevicenumber]   [--mfg|-g  manufacturer  code]
       [--maxtries (comma-separated-list)] [--model|-l model name] [--nodetect]  [--sn|-n  serial
       number]  [  --rw  |  --ro  |  --wo]  [--show-table|--no-table]  [-s|--stats [stats-class]]
       [-t|--terse|--brief|-v|--verbose]  [-U|--show-unsupported]   [--usb|-u   busnum.devicenum]
       [--verify  |  --noverify]  [-V|--version] [h|--help] detect | capabilities | scs | probe |
       getvcp [feature-code|feature-group] |setvcp feature-code new-value ] |  vcpinfo  [feature-
       code|feature-group]   |   dumpvcp   [filename]  |  loadvcp  filename  ]  |  environment  |
       usbenvironment'| interrogate


       ddcutil is used to query and change monitor settings.

       ddcutil communicates with monitors implementing MCCS (Monitor Control Command  Set)  using
       the  DDC/CI  protocol  on the I2C bus.  Normally, the video driver for the monitor exposes
       the I2C bus as devices named /dev/i2c-n.  Alternatively, ddcutil can communicate with  USB
       connected monitors implementing the USB Monitor Control Class Specification.

       The  Monitor  Control  Command  Set  describes a collection of Virtual Control Panel (VCP)
       features that a monitor can implement.  Each feature is identified using  a  single  byte.
       For example, feature x10 is the brightness control.

       In  general, the monitor settings that can be controlled by ddcutil are a superset of what
       can be changed using the buttons on a monitor and its on  screen  display.   The  specific
       capabilities vary from monitor to monitor.

       A  particular  use  case  for  ddcutil  is  as  part of color profile management.  Monitor
       calibration is relative to the monitor color settings currently in effect, e.g. red  gain.
       ddcutil allows color related settings to be saved at the time a monitor is calibrated, and
       then restored when the calibration is applied.

       Another common use case is to switch the monitor input source.

       This man  page  includes  only  abbreviated  documentation  of  trace  and  other  program
       diagnostic facilities.

       For extended documentation, use the "--help" option, and see


       detect Report monitors

       vcpinfo [ feature-code | feature-group ]
              Describe VCP feature codes that ddcutil knows how to interpret

              Query the monitor's capabilities string

       getvcp [ feature-code | feature-group ]
              Report a single VCP feature value, or a group of feature values

       setvcp [+|-] feature-code new-value
              Set  a  single VCP feature value.  If + or - is specified, it must be surrounded by
              blanks, and indicates a relative value change of a Continuous VCP feature.

       dumpvcp filename
              Save color profile related VCP feature values in  a  file.   If  no  file  name  is
              specified, one is generated and the file is saved <describe location>

       loadvcp filename
              Set  VCP  feature  values  from  a  file.   The monitor to which the values will be
              applied is determined by the monitor identification stored in  the  file.   If  the
              monitor is not attached, nothing happens.

              Probe the ddcutil installation environment.

       scs    Issue DDC/CI Save Current Settings request.

       usbenv Probe USB aspects of the ddcutil installation environment.

       probe  Explore the capabilities and features of a single monitor.

              Collect maximum information for problem diagnosis.

              Tests if hiddev device is a USB connected monitor, for use in udev rules.



       A  feature-code  is  specified  by  its  2 character hex feature number, with or without a
       leading "0x", e.g.  0x10, 10


       The following are the most useful feature groups recognized.  For a  complete  list,   use
       the --help option.

              All feature codes understood by ddcutil
       COLOR  Scan color related feature codes
              Subset  of  color  related feature codes that are saved and restored by dumpvcp and
       SCAN   Scan all possible feature codes 0x00..0xff, except those known the be write-only

       Feature group names can be abbreviated to the first 3 characters.  Case is ignored.   e.g.
       COL, pro


       A decimal number in the range 0..255, or hexadeciaml number in the range x00..xff.


       Options for monitor selection.  If none are of these options are specified, the default is
       the first detected monitor.  Options --mfg, --model and --sn can be specified together.
              display-number logical display number (starting from 1)
              bus-number I2C bus number
       -a,--adl adapterIndex.displayIndex
              ADL adapter and display indexes
              device number hiddev device number
       -u,--usb busnum.devicenum
              USB bus and device numbers
              3 letter manufacturer code
              model name
              serial number.  (This is the "serial ascii" field from the  EDID,  not  the  binary
              serial number.)
              256  hex  character  representation of the 128 byte EDID.  Needless to say, this is
              intended for program use.

       Options to control the amount and form of output.
       -t, --terse, --brief
              Show brief detail.  For command getvcp, the output is in machine readable form.
       -v, --verbose
              Show extended detail
       -U, --show-unsupported
              Normally, getvcp does not report unsupported  features  when  querying  a  feature-
              group.  This option forces output.
       --show-table | --no-table
              Normally, getvcp does not report Table type features when querying a feature-group.
              --show-table forces output.   --no-table is the default.
       --rw, --ro, --wo
              Limit getvcp or vcpinfo output to read-write, read-only, or  (for  vcpinfo)  write-
              only features.
       --mccs  MCCS version
              Tailor vcpinfo output to a particular MCCS version, e.g. 2.1

       Options for diagnostic output.
       --stats [all|errors|tries|calls|elapsed|time]
              Report  execution  statistics.   If  no argument is specified, or ALL is specified,
              then all statistics are output.  elapsed is a  synonym  for  time.   calls  implies
              I2C bus communication is an inherently unreliable.  It is the responsibility of the
              program using the bus to manage retries in case of failure.   This  option  reports
              retry counts and various performance statistics.
       --ddc  Reports  DDC  protocol  errors.  These may reflect I2C bus errors, or deviations by
              monitors from the MCCS specification.

       Options for program information.
              Show program help.
       -V, --version
              Show program version.

       Options to tune execution:
       --maxtries (max-read-tries, max-write-read-tries, max-multi-part-tries)
              Adjust the number of retries
              Take control of slave addresses on the I2C bus even they are in use.
       -f, --force
              Do not check certain parameters.
              Verify values set by setvcp or loadvcp. (default)
              Do not verify values set by setvcp or loadvcp.
              If there are multiple monitors, initial checks are performed in  multiple  threads,
              improving performance.
              If the monitor is specified by its I2C bus number (option --busno) skip the monitor
              detection phase, improving performance.


       Requires       read/write       access       to       /dev/i2c        devices.         See


       Some  newer  Nvidia  cards (e.g. GTX660Ti) require special settings to properly enable I2C
       support.   If you are using this driver and ddcctool does not work with your  Nvidia  card
       (TODO: Describe symptoms), you can try the following:

       Copy      file      /usr/local/share/ddcutil/data/90-nvidia-i2c.conf      to     directory

       sudo cp /usr/local/share/ddcutil/data/90-nvidia-i2c.conf /etc/X11/xorg.conf.d

       This file will work "out of the box" if you do not have an /etc/X11/xorg.conf  file.    If
       you  do,  adjust the Identifier value in the file to correspond to the value in the master
       xorg.conf file.

       (Note that the above instructions assume that datadir was  set  to  /usr/local/share  when
       ddcutil was installed.  YMMV)

       For further discussion of Nvidia driver settings, see


       AMD's  proprietary  video  driver fglrx does not expose the I2C bus.  Instead, it provides
       access to the  bus  through  the  AMD  Display  Library,  aka  ADL.   Owing  to  copyright
       restrictions,  the  ADL  header  files  are  not  distributed  with  the  ddcutil  source.
       Additional steps are required to build ddcutil with fglrx support.

       To see if your copy of ddcutil was built with fglrx support, issue the command:
       ddcutil --version

       ADL identifies monitors using an adapter-number/display-number pair.  To select a  monitor
       using  these numbers, specify the --adl option with a period separating the adapter-number
       and display-number, e.g.
       --adl 0.1


       Virtualized video drivers in VMWare and VirtualBox do not provide I2C emulation.   Use  of
       normal video drivers with PCI passthrough is possible.


       ddcutil detect
       Identify all attached monitors.

       ddcutil getvcp supported

       Show all settings that the default monitor supports and that ddcutil understands.

       ddctpp getvcp 10 --display 2
       Query the luminosity value of the second monitor.

       ddcutil setvcp 10 30 --bus 4
       Set the luminosity value for the monitor on bus /dev/i2c-4.

       ddcutil vcpinfo --verbose
       Show detailed information about VCP features that ddcutil understands.

       ddcutil interrogate > ~/ddcutil.out
       Collect  maximum information about monitor capabilities and the execution environment, and
       direct the output to a file.


       Returns 0 on success, 1 on failure.

       Requesting help is regarded as success.


       The project homepage:


       Sanford Rockowitz (rockowitz at minsoft dot com)
       Copyright 2015-2018 Sanford Rockowitz

                                          01 April 2018                                ddcutil(1)