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Date:   Tue, 9 Apr 2019 10:47:19 +0200
From:   Gerd Hoffmann <kraxel@redhat.com>
To:     David Airlie <airlied@redhat.com>
Cc:     David Airlie <airlied@linux.ie>,
        open list <linux-kernel@vger.kernel.org>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        "open list:DRM DRIVER FOR QXL VIRTUAL GPU" 
        <virtualization@lists.linux-foundation.org>,
        "open list:DRM DRIVER FOR QXL VIRTUAL GPU" 
        <spice-devel@lists.freedesktop.org>
Subject: Re: [PATCH] drm/qxl: drop prime import/export callbacks
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  Hi,

> > Should we add something like DRM_PRIME_CAP_SAME_DEVICE?
> 
> Yeah I expect we need some sort of same device only capability, so
> that dri3 userspace can work.
> 
> If we just fail importing in these cases what happens? userspace just
> gets confused, I know we used to print a backtrace if we hit the mmap
> path, but if we didn't do that what happens?

Well, we printed a backtrace and returned -EINVAL.  So it looked a bit
scary due to the backtrace which is usually printed for more serious
problems.  But we also returned a proper error code.

Userspace was not happy.  It was wayland (gnome-shell) which ran into it
it, and it didn't came up with a working display.

cheers,
  Gerd