Regression: drm: Lobotomize set_busid nonsense for !pci drivers (a325725633c2)

[Hans de Goede]

Hi,

On 30-09-16 10:28, Hans de Goede wrote:
> Hi,
>

<snip>

> Xorg when running without a Xorg.conf searches for what it considers
> a "primary" gpu / video-card, basically it attempts to bring up the
> right card in setups where there are multiple cards and if it does not
> find one exits with an error.
>
> The xserver has a 2 step process for finding the primary card:
>
> 1) It searches for is a card which has a vga-bios mapped,
> as we've already determined in the mentioned Red Hat bug that works for
> the classic qemu emulated video-cards, but not for qemu's virtio-vga.
>
> 2) If that does not work Xorg will fallback to any video class device
> on pci-bus 1.
>
> This fallback actually has been broken in the Xorg xserver for quite a
> while now and only 2 days ago a patch from Laszlo was merged to fix this.
>
> Only for things to break again due to this kernel patch.
>
> Since the whole step 2) thingie is very much tied to x86 machines
> where pci-bus 0 used to be the main bus and pci-bus 1 the agp,
> which is sorta an obsolete assumption now a days and  since relying
> on bus numbers / enumeration order is a bad idea in general I'm not
> entirely sure if this counts as a regression.
>
> I've discussed the problem of the xserver exiting with an error when
> no primary device can be found with some people (ajax) at XDC last week
> since there are other use-cases where the pci-bus 1 fallback does not
> work.
>
> As such I've been working on a xserver patch-set to make the xserver
> try harder (pick the first available device) when both steps described
> above fail to find one, which should make things work even with the
> newest (broken / regressed) kernels.
>
> Given this mail thread, I guess I'm working after all today (I had
> planned a day off) and I'll try to wrap up this patch-set and reply
> to this mail with the server patches attached for Joachim and/or
> Laszlo to test.

Attached are 2 patches against the xserver which should fix this,
please give them a try.

Regards,

Hans
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