[PATCH] modesetting: fail PreInit() if the device has zero connectors

[Hans de Goede]

Hi,

On 03-11-17 17:56, Giuseppe Bilotta wrote:
> On Fri, Nov 3, 2017 at 10:09 AM, Hans de Goede <hdegoede at redhat.com> wrote:
>> Weird, on my XPS15 9550 where the nvidia GPU does not have/drives any
>> outputs
>> I do get 2 devices in xrandr --listproviders as expected. You may want to
>> start
>> with figuring out why the normal setup where you load nouveau normally is
>> not
>> working. Perhaps once that works, it will also powerdown the GPU properly.
> 
> I have an XPS15 9350 with a similar situation. You get two devices if
> nouveau is loaded before Xorg starts.
> 
> If I understand Tobias' mail, his situation is with nouveau modprobed
> _while X is running already_, not if it's loaded before X starts. I've
> tried it in the past and I got the same segfaults that he is getting.
> I have AutoAddGPU set to false specifically to avoid this segfault,
> since I use a similar setup (no driver loaded, modprobe as needed),
> although in my case it's more out of a need to be able to switch to
> nvidia's proprietary as-needed.
> 
> In my case I have verified that without loading nouveau or nvidia the
> GPU is powered up, which is supoptimal battery-wise, and I'm not sure
> nvidia powers down the GPU while not in use (nouveau does, byt to me
> is mostly useless, because the performance it achieves on the dGPU is
> less than the one I get on Intel's iGP, and I still need the nvidia
> one for CUDA), but as Tobias mentioned, that's a separate issue from
> the segfault that comes from runtime nouveau modprobing.

Right, so the thing to fix here is pin down where the segfault from
runtime nouveau probing comes from and fix that, so that once
modprobed things work the same as they do when nouveau is loaded
before X starts.

Regards,

Hans