Ubuntu Manpage: ddcutil - Query and change monitor settings

NAME

       ddcutil - Query and change monitor settings

SYNOPSIS

       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

DESCRIPTION

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 http://www.ddcutil.com.

COMMANDS

detect Report monitors

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

capabilities
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.

environment
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.

interrogate
Collect maximum information for problem diagnosis.

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

COMMAND ARGUMENTS

       feature-code

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

       feature-group

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

       ALL|KNOWN
              All feature codes understood by ddcutil
       COLOR  Scan color related feature codes
       PROFILE
              Subset of color related feature codes that are saved and restored by dumpvcp and loadvcp
       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

       new-value

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

OPTIONS

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.
-d,--display
display-number logical display number (starting from 1)
-b,--bus
bus-number I2C bus number
-a,--adl adapterIndex.displayIndex
ADL adapter and display indexes
--hiddev
device number hiddev device number
-u,--usb busnum.devicenum
USB bus and device numbers
-g,--mfg
3 letter manufacturer code
-l,--model
model name
-n,--sn
serial number. (This is the "serial ascii" field from the EDID, not the binary serial number.)
-e,--edid
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 time.
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.
-h,--help
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
--force-slave-address
Take control of slave addresses on the I2C bus even they are in use.
-f, --force
Do not check certain parameters.
--verify
Verify values set by setvcp or loadvcp. (default)
--noverify
Do not verify values set by setvcp or loadvcp.
--async
If there are multiple monitors, initial checks are performed in multiple threads, improving
performance.
--nodetect
If the monitor is specified by its I2C bus number (option --busno) skip the monitor detection
phase, improving performance.

EXECUTION ENVIRONMENT

       Requires read/write access to /dev/i2c devices.  See http://www.ddcutil.com/i2c_permissions.

NVIDIA PROPRIETARY DRIVER

       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 /etc/X11/xorg.conf.d

       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 http://www.ddcutil.com/nvidia.

AMD PRORIETARY DRIVER

       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

VIRTUAL MACHINES

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

EXAMPLES

       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.

DIAGNOSTICS

       Returns 0 on success, 1 on failure.

       Requesting help is regarded as success.

AUTHOR

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

                                                  01 April 2018                                       ddcutil(1)