USB3 Display Driver, Raspberry Pi2, and Expectations

[Cotonou]

Hey there.

I've been waiting for the DisplayLink USB3 display driver for a bit now, and am very happy the beta version has been released!

I have an Raspberry Pi 2 I've been saving to pair with my AOC 1659 monitor and I've given it a go. The rPi2 is running Ubuntu 14.04, and of course is equipped with an ARM processor.

Unfortunately I'm not running into a huge amount of success in getting the driver to work. I've provided the install package with all the dependencies it complained about. It successfully completes and attempts to start the display service, but the syslog tells me that it immediately crashes out.

In the syslog, I find small stack of errors all looking more or less like this:

evdi: Unknown symbol drm_framebuffer_cleanup (err 0)
evdi: Unknown symbol drm_kms_helper_poll_fini (err 0)
evdi: Unknown symbol drm_open (err 0)
evdi: Unknown symbol drm_mode_vrefresh (err 0)
evdi: Unknown symbol drm_fb_helper_single_add_all_connectors (err 0)
evdi: Unknown symbol drm_fb_helper_init (err 0)

Which obviously points to something having to do with the DRM module, but unfortunately this is where my investigations run into a wall. I have noticed a few lines in the release notes that imply the driver only works on x86 processors at the moment, which would be sad if true. My question is if it is even possible to get the beta displaylink drivers working on a Raspberry Pi2, and if so perhaps some advice on what my next move should be.

Thanks for your time.

[mlukaszek]

The rPi2 is running Ubuntu 14.04, and of course is equipped with an ARM processor.

Hi,

There are few things that would need work:

evdi will only work on a system which uses drivers compatible with DRM
evdi has dependencies on drm_kms_helper and drm modules, and needs symbols from them, hence the errors you see

evdi: Unknown symbol drm_framebuffer_cleanup (err 0)
evdi: Unknown symbol drm_kms_helper_poll_fini (err 0)
evdi: Unknown symbol drm_open (err 0)
evdi: Unknown symbol drm_mode_vrefresh (err 0)
evdi: Unknown symbol drm_fb_helper_single_add_all_connectors (err 0)
evdi: Unknown symbol drm_fb_helper_init (err 0)


finally, as you already saw in the release note, the helper application currently only works on Intel platform. Providing ARM support is not impossible, but the driver is targeted at desktop Linux environments, which are Intel based and we're not looking at extending support to ARM at this time. That said, things may change if someone proves that evdi is ready to go and the only component that's left to do is DisplayLink Manager. Feel free to raise an Idea for this through our support page (http://support.displaylink.com) - that would help us see how much demand there is for this.


Hope this helps,
Michal

[mlukaszek]

If someone feels like experimenting, this is probably a good starting point...

https://www.phoronix.com/scan.php?page=news_item&px=RPi-No-3D-Driver-Review

Cheers,
Michal