Do these camera support long exposures? I don't see how this could be done using the V4L2 interface.

DMK should be able to make images of long exposure (up to 60 minutes with IC Capture software), but for now it does not work. I get a black image

Here is the tab setting for long exposure. I tried various settings with no results yet

That tab is meant for modded cams I think, I will have to verify with the author. I'm still researching whether there is a way in V4L to set manual exposure if possible.

Tab long exposure is rather complex to deal with, apart from the enable / disable button, I have no idea of ​​the proper configuration for the other settings. Indeed it seems reserved for advanced users and modded cameras.
Now it would be nice if we could just manage native long exposure cameras like mine ... Thank you for your help!

This has been addressed now by Jean-Luc. There is an option now for exposure in V4L2 Control called "Exposure (Absolute)". You also need to set exposure to Manual. But whether this particular V4L2 control is implemented for the DMK UVC driver I don't know, you'd have to try and find out if it works.

Not having found the V4L2 Control setting Called "Exposure (Absolute)" in INDI, I tested in guvcviewer that offers manual or auto exposure options and the famous exposure setting (absolute value)
And it works! It took me time to understand what scale was used for the absolute exposure, I remembered that the shortest exposure time of the camera is 1/10000 second, which corresponds here to the number 1. 1 seconds exposure equals 10000, 10 seconds, 100,000, etc.. And the maximum exposure of 60 minutes for the DMK camera is equivalent to 36 million.
The other options in guvcviewer correspond to what is possible for me to set on Windows: brightness (0 to 63), the gain (260-1023), gamma (1 to 500)

Are you sure you are using the latest libindi (from SVN, not PPA)? Can you post a screenshot of the V4L control tab?

Here is how the V4L2 tab looks:

No manual exposure control, or the setting of exposure in absolute value

Oh wait, the ppa offered me an update today... I reinstall via svn

Ok it works! The V4L2 tab contains exposure in absolute value and tab options V4L2 offers manual or auto mode. By cons, under Ekos in the CCD tab, the exposure setting is ineffective. Setting panel INDI prevails over Ekos. This is not really a problem, adjusting the exposure time is more accurate with INDI

Ok, I wanted a confirmation before updating the V4L2 driver. The driver will update "absolute exposure" value if it exists whenever a new exposure is requested, so the Ekos "expsoure" setting will be sufficient by itself.