Provided by: ddcutil_0.8.6-1_amd64 
NAME
ddcutil - Query and change monitor settings
SYNOPSIS
ddcutil [--display|--dis|-d dispno] [--bus|-b busno] [--adl|-a adapter-index.display-index] [--hiddev
hiddevdevicenumber] [--usb|-u busnum.devicenum] [--edid 256 hex character EDID] [--mfg|-g manufacturer
code] [--model|-l model name] [--sn|-n serial number] [--noverify] [-v|--verbose] [-t|--terse|--brief]
[-U|--show-unsupported] [--ddc] [-s|--stats] [--trace trace-class] [--timestamp|--ts] [--maxtries
commaseparatedlist] [--force-slave-address] [-f|--force] [--async] [--nodetect] [-V|--version] [h|--help]
detect | listvcp | capabilities | getvcp | probe [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.
For extended documentation, see http://www.ddcutil.com.
COMMANDS
detect Report attached 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
dumpvcp filename
Save color 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.
usbenv Probe USB aspects of the ddcutil installation environment.
probe Explore the capabilities and features of a sing 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 All feature codes understood by ddcutil
KNOWN Scan all understood feature codes, but show only codes supported by the monitor
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 number in the range 0..255
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.
-U, --show-unsupported
Normally, getvcp does not report unsupported features when querying a feature-group. This option
forces output.
-t, --terse, --brief
Show brief detail. For command getvcp, the output is in machine readable form.
-v, --verbose
Show extended detail
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.
--trace trace-class
Enable debug tracing for a trace class. Valid values are: base, i2c, adl, ddc, main, and the
special value all. Some trace classes are more useful than others.
Specify this option multiple times to enable multiple trace classes.
--timestamp, --ts
Prepend trace messages with elapsed time
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-read-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 package i2c-dev
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)
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 in a virtual machine has not been tested.
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.
SEE ALSO
The project homepage: http://www.ddcutil.com
AUTHOR
Sanford Rockowitz (rockowitz at minsoft dot com)
Copyright 2015-2016 Sanford Rockowitz
15 December 2015 ddcutil(1)