Fwd: [from tech.openbsd.org] DisplayLink compatibility and performance issues

[Sławomir Gonet]

Hello everyone,

I just wanted to crosspost this from OpenBSD tech@ list as I am afraid
there's no one able to solve my problem – hope you will be more lucky :)

I know this is very OpenBSD-specific, but maybe you will be able to
introduce me somehow.

Cheers,
Slawek

Sławomir Gonet <slawek at otwiera.cz> writes:

> Hi everyone,
>
> I've recently bought DisplayLink device[1]. According to [2], it
> might/should work under OpenBSD so I gived it a try. My results are:
>
> 1) Not detected USB PID - I've added it as new device to kernel's udl
>    driver.
> 2) Conflict with bulit-in Intel HD graphics card.
>    I spent some time debugging why xf86-video-wsudl is not detecting my
>    DL-165 adapter. After downloading xenocara I was debugging wsudl and
>    what I found:
>    
>    WsudlProbe():
>    driver/xf86-video-wsudl/src/wsudl_driver.c:309 calls "xf86ClaimFbSlot()"
>
>    xf86ClaimFbSlot()
>    xserver/hw/xfree86/common/xf86fbBus.c:62 checks if pciSlotClaimed is
>    true.
>
>    And, unfortunately, on my platform pciSlotClaimed == 1, because of
>    intel driver. However, things started to work when before calling
>    xf86ClaimFbSlot() I've set pciSlotClaimed to 0.
> 3) UDL device does not get auto-detected
>    I had to define UDL device manually in xorg.conf and connect screens
>    using Xinerama to make it working
> 4) Resolution problems with Intel - maybe because of hacking from point
>    2 in random situations intel driver fails and messes up resolution on
>    one of the screens - about 3/4 of screen become "unusable". No idea
>    how to explain it.
> 5) Performance
>    What I've found: [3] - so more or less "It will not work, no
>    way". But under Linux there are no performance issues at all. I can
>    even play video (but not in fullscreen), 1080p works great. Where's
>    the bottleneck in OpenBSD? I am not even able to move window on the
>    desktop smoothly, in idle Xorg process consumes 5-10% of CPU with
>    peaks up to 40%.
>
> Further informations about my platform:
> - Lenovo ThinkPad t420s with Intel i7.
> - 2× BENQ G2420HD
> - i-tec 2.0 TRIO USB to DVI (DisplayLink DL-165 inside)
>
> Unfortunately, I am really newbie in both OpenBSD and kernel
> development, so I am afraid that debugging like this is everything I am
> able to. Are there any active developers of wsudl driver? Issues 4 and 5
> are fatal to me, I need two displays - do you have any ideas how to move
> things forward here?
>
> Regards,
> Slawek
>
>
> [1] - http://www.i-tec-europe.eu/?t=3&v=130
> [2] - http://libdlo.freedesktop.org/wiki/
> [3] - http://openbsd.7691.n7.nabble.com/Xorg-wsudl-4-DL-165-consumes-a-lot-of-cpu-td224195.html
>

Sławomir Gonet <slawek at otwiera.cz> writes:

> Is there any reason why claiming framebuffer slot cannot be done while
> having (another) PCI device already claimed? Also, I have no idea where
> Intel driver claims this device - I am not able to find corresponding
> code in xf86-driver-intel.

-- 

SG
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