Linux's Display Brightness/Backlight Interface Is Finally Being Overhauled

[oiaohm]

I have a Samsung monitor but nothing in the datasheet, also not controllable over Windows or Xbox, so I guess Samsung doesn't care about such stuff.

A standard would be good, but one that makes it mandatory for at least HDMI and display port. Because as long as it's optional it will stay this way.

Samsung is one of the cursed. You need to open up the manual. Some have MCCS over USB and no dcc/ci or hdmi CEC on the HDMI or Displayport. Some only have dcc/ci on a particular port and none of the others like it could be the 1 of the display ports and none of the others with dcc/ci.

Some samsung monitors models you have to use dcc/ci because they don't have any buttons at all. That right you can only power on and off the monitor by dcc/ci so these monitors are serous problems when you are having UEFI problems and its the only monitor.

Samsung monitors are a total mixed bag. Samsung in manual will refer to DCC/CI support as Magictune and this has big habit of being non standard DCC/CI controls as they expect you to use the Samsung own software under Windows. Also lot of samsung monitors will disable their DCC/CI if you attempt to send messages faster than they like as well.

This is a cursed mess non standard mess. Samsung is model to model and more often than not non standard and touchy if they have dcc/ci. Some samsung monitors will be hdmi CEC with complete custom commands. When I say complete custom commands I mean magictune or reversed are going to be able to have the hdmi CEC do something useful. Xbox support or playstation support in manual with hdmi CEC is good because this says at-least some of the standard commands should be there.

We really do need standard body and reviewers to be checking out monitor CEC and dcc/ci and be calling them out when implementations are basically intentionally unstable/not usable..

Of course your monitor Anux could be a samsung monitor with nothing as in no CEC no dcc/ci and no MCCS over USB. Samsung selectively cares about CEC and dcc/ci and MCCS they do like there vendor lockins at times.

[Anux]

Many monitor/tv vendors are not making it simple to know if you can control you monitor/tv from your computer or game console. Please note most game consoles want hdmi/CEC not DDC/CI to allow the console to control monitor/tv brightness and so on.

Yes if the DDC/CI appears on datasheet or manual basic functionality normally there done in standard ways like muting audio if monitor has speakers selecting inputs and brightness controls. If DDC/CI does not appear on datasheet or manual and it has DDC/CI you are likely to find like the MSI where there is fairly much only vendor unique interfaces.

I have a Samsung monitor but nothing in the datasheet, also not controllable over Windows or Xbox, so I guess Samsung doesn't care about such stuff.

A standard would be good, but one that makes it mandatory for at least HDMI and display port. Because as long as it's optional it will stay this way.

[oiaohm]

Those this stuff appear in datasheets? I've never seen it.

https://www.lg.com/us/business/download/resources/BT00001837/BT00001837_640.pdf

Yes it appears on the datasheets with some vendors if they have the DDC/CI or hdmi/CEC when it a monitor or tv but not all. Notice that LG call their hdmi/CEC simplelink on the TV box fun part is that you at times have to disable simplelink to have hdmi/CEC option appear to enable to allow raspberry pi or equal to control the tv. hdmi/CEC you have the fun of who wants to be big chief sitting bull problem.

MSI it in their monitor manuals if the monitor support it hdmi/CEC. MSI monitors mostly don't fully support DDC/CI yes this includes not having brightness controls over DDC/CI. Yes you can download the manual before you buy the monitor.

https://download.msi.com/archive/mnu_exe/monitor/Optix_G273QF_G273QPFv1.0_English.pdf

MSI for example is one where you have to get the monitor manual and search it for CEC to see if it has CEC.
Do note the specification sheet of the MSI Optix G273QF that hat is the manual of does not list it has CEC support. Yes MSI here has brightness control by CEC to the hdmi CEC standard even over the display-ports.

Anux this is just a total level of mess. It is quite annoying that some vendors only put a cut down feature list on the datasheets and the full feature list is in the manual. Then there are vendors like MSI that datasheet is incomplete and the manual is incomplete. Please note MSI is not the only vendor out there like this.

That the fun part just because a monitor has DDC/CI does not mean that is how you are are able to control brightness or inputs or any other feature the DDC/CI may be only for vendor monitor calibration(that is nicely undocumented).

Many monitor/tv vendors are not making it simple to know if you can control you monitor/tv from your computer or game console. Please note most game consoles want hdmi/CEC not DDC/CI to allow the console to control monitor/tv brightness and so on.

Yes if the DDC/CI appears on datasheet or manual basic functionality normally there done in standard ways like muting audio if monitor has speakers selecting inputs and brightness controls. If DDC/CI does not appear on datasheet or manual and it has DDC/CI you are likely to find like the MSI where there is fairly much only vendor unique interfaces.

The reality here you are needing both DDC/CI and hdmi/CEC because it depend on what you have connected for what one you need to control the monitor/tv from the computer. Yes monitors with non functional DDC/CI but with functional hdmi/CEC exist and there are some that are really wacky that the hdmi/CEC does not work over the hdmi ports as you expect but its tunneled on the displayport.

Anux this is a really bad state of play. This is why I wish Vesa or equal for standard approval would add that functional DDC/CI or hdmi/CEC was mandatory with mandatory min functionality done as per the standards.

[Anux]

You do need to check that its on the feature list.

Those this stuff appear in datasheets? I've never seen it.

[oiaohm]

I've tried several branded monitors made in the last decade or so (such as HP, Beng, LG, Dell) and they at least support DDC/CI

I can tell you for sure you have been lucky. LG for sure still make some monitors with zero DDC/CI support new and these are not TVs I happen of bought one because in stock and slightly cheaper that was a mistake(yes about 20USD price difference between one with DDC/CI and one without) so I am really kicking myself know that I did not know about DDC/CI when I bought monitor 2 years ago. You do need to check that its on the feature list. If it a LG TV it is 100 percent you don't have DDC/CI instead have to use hdmi/CEC if it has that again check that its on the feature list.

Normal end users really don't want to have to think is this a TV or is this Monitor they more want to plug in item and have it work.

So far I've only encountered one external monitor that lacks DDC/CI entirely: a cheap IPS LCD purchased from Aliexpress. It's pretty barebones, I can see the backlight shining through the vesa mount holes.

Lot of them will turn out to support hdmi/CEC because a lot of them turn out to be TV controller boards.. Also look closer does the IPS LCD panel have anti-glare treatment. Monitor panels from factory in most cases get anti-glare treatment and TV IPS LCD panels don't. Lot of those are basically TVs without the tuner. Yes panel designed for TV is going to be matched up with controller made for TV.

Really I would love like hdmi and displayport standards to mandate something be there. As pick either DDC/CI or hdmi/CEC and say all monitors/tv newer than this standard must have it and the functionality will be tested as part of certification.

The mess of DDC/CI and hdmi/CEC is where we do need standard body to step up.

[digitaltrails]

I wish all desktop environments at least had a checkbox in display settings to disable monitor auto detection in order to prevent all these issues from happening.

Interestingly, Mate is the only DE that didn't give me any issues with power cycling. It also has a "detect monitor" button in its display settings, which implies that it works more like on Windows.

KDE's attempts to move windows around can be disabled by turning off the kscreen2 service.

How a monitor is connected to the desktop may also make a difference. If I recall correctly, kscreen2 responds to Displayport monitors being turned off and doesn't appear to notice for HDMI or DVI.

I don't think a lot of this stuff: brightness, colour, HiDPI mixed-DPI, has been well thought out, it's a mess. I think this is partly that experiences of key desktop developers vary considerably depending on what is present on their own desktop. In my own universe, I have absolutely no experience of using current desktops on a laptop.

[digitaltrails]

But then if you eg unplug your laptop with a monitor plugged in to work elsewhere, you can't access or move the windows that were open on the other monitor.

I'm used to window managers that can display an overview - such as KDE's the virtual desktop overview in the task-bar. In which case, off-screen windows can be dragged somewhere useful. As a result, I do prefer my windows stay where I put them.

[digitaltrails]

Back on topic: why is it not possible to do this on regular desktop monitors?

See https://www.ddcutil.com/, https://github.com/digitaltrails/vdu_controls (I wrote vdu_controls - a mini system-tray accessory front end to ddcutil, works on KDE, gnome, deepin and others).

Ddcutil seems robust. I've managed to use it with a variety of monitors and have helped several others get ddcuti/vdu_controls going with monitors with more cranky DDC/CI implementations. The author of ddcutil has also written a comprehensive DDCUI GUI.

Plus there are other implementations of DDC/CI such as https://github.com/ddccontrol/ddccontrol and other GUI's such as https://github.com/newAM/monitorcontrol. Neither of which I have tried. I think there may be more DDC/CI utilities out there.

[digitaltrails]

That a new one to me none of my monitors in fact support DDC/CI.

https://www.ddcutil.com/monitor_notes/

Yes DDC/CI is still a huge non standard mess.

Ddcutil may work with many external monitors not in the supported list.

I've tried several branded monitors made in the last decade or so (such as HP, Beng, LG, Dell) and they at least support DDC/CI for brightness and contrast. In other cases, some tweaking may help. I've written my own system tray front end to ddcutil (https://github.com/digitaltrails/vdu_controls) which attempts to work around DDC/CI implementations that are incomplete to at least provide brightness and contrast.

So far I've only encountered one external monitor that lacks DDC/CI entirely: a cheap IPS LCD purchased from Aliexpress. It's pretty barebones, I can see the backlight shining through the vesa mount holes.

[Anux]

If the monitor you connected supports the resolution of a saved set of panes, give the user the option to move them onto the newly attached monitor. Actually, include even the non-matching panes, with a warning that windows may get rearranged!

That would be a nice solution, but to combine this with extended monitors (two monitors acting as one) would be really hard with many edge cases.