From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1756073AbcEaG31 (ORCPT <rfc822;w@1wt.eu>);
	Tue, 31 May 2016 02:29:27 -0400
Received: from mx1.redhat.com ([209.132.183.28]:35310 "EHLO mx1.redhat.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1755908AbcEaG3X convert rfc822-to-8bit (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Tue, 31 May 2016 02:29:23 -0400
Message-ID: <1464676160.5978.24.camel@redhat.com>
Subject: Re: [PATCH] Add virtio gpu driver.
From: Gerd Hoffmann <kraxel@redhat.com>
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>
Date: Tue, 31 May 2016 08:29:20 +0200
In-Reply-To: <20160530144755.GK27098@phenom.ffwll.local>
References: <1427213239-8775-1-git-send-email-kraxel@redhat.com>
	 <20150324165057.GN1349@phenom.ffwll.local>
	 <1427718227.3372.33.camel@nilsson.home.kraxel.org>
	 <20150330144927.GN23521@phenom.ffwll.local>
	 <CAKMK7uFUNT193f5djZD6T8cgRxxnZL73yrqbupPHOd2P-+Y=pQ@mail.gmail.com>
	 <1464335302.10663.10.camel@redhat.com>
	 <20160527090313.GX27098@phenom.ffwll.local>
	 <1464616236.5179.41.camel@redhat.com>
	 <20160530144755.GK27098@phenom.ffwll.local>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 8BIT
Mime-Version: 1.0
X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Tue, 31 May 2016 06:29:23 +0000 (UTC)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

  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