linux-kernel - Re: [RFC v2 5/8] drm/fence: add in-fences support

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Message-ID: <20160428175124.GG4329@intel.com>
Date:	Thu, 28 Apr 2016 20:51:24 +0300
From:	Ville Syrjälä <ville.syrjala@...ux.intel.com>
To:	Daniel Vetter <daniel@...ll.ch>
Cc:	Gustavo Padovan <gustavo@...ovan.org>,
	Daniel Stone <daniel@...ishbar.org>,
	Greg Hackmann <ghackmann@...gle.com>,
	Gustavo Padovan <gustavo.padovan@...labora.co.uk>,
	Daniel Stone <daniels@...labora.com>,
	Riley Andrews <riandrews@...roid.com>,
	dri-devel <dri-devel@...ts.freedesktop.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Arve Hjønnevåg <arve@...roid.com>,
	John Harrison <John.C.Harrison@...el.com>
Subject: Re: [RFC v2 5/8] drm/fence: add in-fences support

On Thu, Apr 28, 2016 at 07:43:16PM +0200, Daniel Vetter wrote:
> On Thu, Apr 28, 2016 at 6:56 PM, Ville Syrjälä
> <ville.syrjala@...ux.intel.com> wrote:
> >>  - better for tracing, can identify the buffer/fence promptly
> >
> > Can fences be reused somehow while still attached to a plane, or ever?
> > That might cause some oddness if you, say, leave a fence attached to one
> > plane and then do a modeset on another crtc perhaps which needs to turn
> > the first crtc off+on to reconfigure something.
> 
> Fences auto-disappear of course and don't stick around when you
> duplicate the drm_plane_state again. I still don't really get the real
> concerns though ...

Properties that magically change values shouldn't exist IMO. I guess if
you could have write-only properties or something it migth be sensible?

> In the end it's purely a transport question, and
> both ABI ideas work out semantically exactly the same in the end. It's
> just that at least in my opinion FENCE_FD prop is a lot more
> convenient.
> -Daniel
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch

-- 
Ville Syrjälä
Intel OTC