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

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Message-ID: <20160426143635.GW8291@phenom.ffwll.local>
Date:	Tue, 26 Apr 2016 16:36:36 +0200
From:	Daniel Vetter <daniel@...ll.ch>
To:	Gustavo Padovan <gustavo.padovan@...labora.co.uk>
Cc:	Ville Syrjälä 
	<ville.syrjala@...ux.intel.com>,
	Gustavo Padovan <gustavo@...ovan.org>,
	Daniel Stone <daniels@...labora.com>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Riley Andrews <riandrews@...roid.com>,
	dri-devel@...ts.freedesktop.org, 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 Tue, Apr 26, 2016 at 11:14:22AM -0300, Gustavo Padovan wrote:
> 2016-04-26 Ville Syrjälä <ville.syrjala@...ux.intel.com>:
> 
> > On Mon, Apr 25, 2016 at 07:33:25PM -0300, Gustavo Padovan wrote:
> > > From: Gustavo Padovan <gustavo.padovan@...labora.co.uk>
> > > 
> > > There is now a new property called FENCE_FD attached to every plane
> > > state that receives the sync_file fd from userspace via the atomic commit
> > > IOCTL.
> > 
> > I still don't like this property abuse. Also with atomic, all passed
> > fences must be waited upon before anything is done, so attaching them
> > to planes seems like it might just give people the wrong idea.
> 
> I'm actually fine with this as property, but another solutions is use
> an array of {plane, fence_fd} and extend drm_atomic_ioctl args just like
> we have done for out fences. However the FENCE_FD property is easier to
> handle in userspace than the array. Any other idea?

Imo FENCE_FD is perfectly fine. But what's the concern around giving
people the wrong idea with attaching fences to planes? For nonblocking
commits we need to store them somewhere for the worker, drm_plane_state
seems like an as good place as any other.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch