xrandr providers and offloading to displaylink usb card

[Aaron Plattner]

On 03/18/2013 10:08 AM, Sam Lanning wrote:
> On 07/01/13 07:03, Dave Airlie wrote:
>> On Mon, Jan 7, 2013 at 10:23 AM, Sam Lanning <sam at samlanning.com> wrote:
>>> Hi There,
>>>
>>> I have a displaylink usb adapter which i have been trying to get working
>>> with my setup for a while.
>>>
>>> when i run
>>>
>>>> xrandr --listproviders
>>> i get the output
>>>
>>>> Providers: number : 2
>>>> Provider 0: id: 106 cap: 0xb, Source Output, Sink Output, Sink Offload
>>>> crtcs: 2 outputs: 4 associated providers: 1 name:Intel
>>>> Provider 1: id: 68 cap: 0x2, Sink Output crtcs: 2 outputs: 3 associated
>>>> providers: 1 name:modesetting
>>> and after running the command
>>>
>>>> xrandr --setprovideroutputsource 68 106
>>> I get 3 new outputs added to xrandr:
>>>
>>>> LVDS-0 disconnected
>>>> VGA-0 disconnected
>>>> HDMI-0 disconnected
>> that doesn't seem like displaylink to me, the driver will never create
>> LVDS outputs.
>>
>> Might want to confirm with a copy of the log file.
>>
>> Dave.
> Hey,
>
> It's been a while (busy with academia) but now i have some time to try
> and get this working again.
>
> I'm running on a laptop with optimus, i believe that the second provider
> listed above is actually my nvidia card. Now i am aware that the hdmi
> port is connected only to the nvidia card, this would match up nicely
> with what i have above, i.e. i activated my nvidia card, hence
> activating my hdmi output, along with the outputs of the other display
> ports (which are connected to both cards)
>
> So it seems my problem at the moment is this:
>
> I have (what i believe to be) the latest display link drivers installed.
> When i plug in my usb gpu, i have a new device listed under lsusb:
>
>> Bus 002 Device 008: ID 17e9:01d7 DisplayLink
>
> And a new corresponding framebuffer device /dev/fbx appears (although
> interestingly it is fb1 sometimes if plugged in at boot).
>
> So my question is, why is it not appearing after calling xrandr
> --listproviders (which shows only my integrated and nvidia cards). Any
> help would be greatly appreciated.

There are two DisplayLink drivers: udl, and udlfb.  In my experience, 
the udlfb one creates a /dev/fb* device and is *not* a DRM driver.  You 
need to unload and/or blacklist that one to let the udl driver do its thing.

The udl driver creates outputs named DVI-*, even if it's really a VGA 
device.

-- 
Aaron