xrandr providers and offloading to displaylink usb card

[Sam Lanning]

On 18/03/13 21:27, Aaron Plattner wrote:
> 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.
>
Thanks Aaron

Ok so i unloaded and blocked udlfb. I am now getting sporadic results.
Sometimes i can see my nvidia card in --listproviders and other times i
can not. And I am still unable to get the displaylink adapter to appear
in listproviders.

I had one success though, in one instance in a fresh boot with udlfb
blacklisted (udl also did not load automatically) i called modprobe udl,
plugged in the displaylink usb gpu and it, along with the nvidia and
intel cards appeared in --listproviders. I have been unable to reproduce
this, and have since only been able to see the integrated intel card in
this listing.

I'm not entirely sure as to what is going on here, partiularly with the
nvidia card sometimes showing up and sometimes not!

Sam.