From mboxrd@z Thu Jan  1 00:00:00 1970
From: Gerd Hoffmann <kraxel@redhat.com>
Subject: Re: [PATCH] Add virtio gpu driver.
Date: Tue, 31 May 2016 08:29:20 +0200
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To: Daniel Vetter <daniel@ffwll.ch>
Cc: virtio-dev@lists.oasis-open.org, "Michael S. Tsirkin" <mst@redhat.com>, "open list:ABI/API" <linux-api@vger.kernel.org>, Rusty Russell <rusty@rustcorp.com.au>, open list <linux-kernel@vger.kernel.org>, "open list:DRM DRIVERS" <dri-devel@lists.freedesktop.org>, "open list:VIRTIO CORE, NET..." <virtualization@lists.linux-foundation.org>, Dave Airlie <airlied@redhat.com>
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  Hi,

> > Why attach the hotspot to the plane?  Wouldn't it make more sense to
> > make it a framebuffer property?
> 
> We don't have properties on the framebuffer. I guess you /could/ just add
> it internally to struct drm_framebuffer, and not bother exposing to
> userspace. I guess that would be a lot simpler,

Yes.  I can simply stick the hotspot into drm_framebuffer in
drm_mode_cursor_universal() and pick up the values in the driver's plane
update function.

>  but it also means that
> atomic userspace can't use hotspots before we add properties to fbs. And
> doing that is a bit tricky since drm_framebuffer objects are meant to be
> invariant - this assumption is deeply in-grained into the code all over
> the place, everything just compares pointers when semantically it means to
> compare the entire fb (including backing storage pointer/offsets and
> everything).

Hmm, the hotspot location for a given cursor image is invariant too, so
I don't think that would be a big issue.

I'd expect userspace define a bunch of cursors, then switch between them
(instead of defining a single cursor, then constantly updating it).

cheers,
  Gerd