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Jim2220 · 08-05-2016, 05:11 PM

I have written a program to output to a Xenarc 700TSU which contains a Displaylink. My program uses libdlo which uses libusb 1.0.20. After booting Linux Mint 17.2 and starting my application Mint makes a USB hotplug sound, the display moves from all blue then briefly flashes what my program sends it. But about 1 second later, the display goes back to blue, the hotplug sound happens again, and I get an error when my program attempts further output.

Here is why I believe this behavior has something to do with the udl module and Displaylink support for Windows plug and play:
If I do this experiment again with the Linux utility "Disks", I notice that after boot the Displaylink appears as a CD in the list of storage devices that are online! I also notice that lsmod does not initially show the presence of udl. lsusb shows
Bus 002 Device 005: ID 17e9:0199 DisplayLink

When I run my program, the Disks screen updates and the Displaylink as a CD rom disappears. But shortly thereafter when the Xenarc screen goes back to blue, Disks updates to again show Displaylink as a CD. udl appears when I run lsmod.

When libusb makes ioctrl calls what device or software is being addressed, udl or is it somehow being bypassed and I'm talking directly to the Displaylink?
Since udl is somehow being enabled did it load from the Displaylink CD Drive?
If so, how can my program get udl loaded and accessable to libusb, then get the Displaylink CD Drive out of the way?

08-05-2016, 05:11 PM	#1
Jim2220 Junior Member Join Date: Nov 2015 Posts: 11	udl module, essential? comes from where? I have written a program to output to a Xenarc 700TSU which contains a Displaylink. My program uses libdlo which uses libusb 1.0.20. After booting Linux Mint 17.2 and starting my application Mint makes a USB hotplug sound, the display moves from all blue then briefly flashes what my program sends it. But about 1 second later, the display goes back to blue, the hotplug sound happens again, and I get an error when my program attempts further output. Here is why I believe this behavior has something to do with the udl module and Displaylink support for Windows plug and play: If I do this experiment again with the Linux utility "Disks", I notice that after boot the Displaylink appears as a CD in the list of storage devices that are online! I also notice that lsmod does not initially show the presence of udl. lsusb shows Bus 002 Device 005: ID 17e9:0199 DisplayLink When I run my program, the Disks screen updates and the Displaylink as a CD rom disappears. But shortly thereafter when the Xenarc screen goes back to blue, Disks updates to again show Displaylink as a CD. udl appears when I run lsmod. When libusb makes ioctrl calls what device or software is being addressed, udl or is it somehow being bypassed and I'm talking directly to the Displaylink? Since udl is somehow being enabled did it load from the Displaylink CD Drive? If so, how can my program get udl loaded and accessable to libusb, then get the Displaylink CD Drive out of the way?