linux-kernel - Re: [RFC 0/5] rework fences on struct sync

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Message-ID: <20160624131724.GA2503@joana>
Date:	Fri, 24 Jun 2016 10:17:24 -0300
From:	Gustavo Padovan <gustavo@...ovan.org>
To:	Christian König <christian.koenig@....com>
Cc:	dri-devel@...ts.freedesktop.org, marcheu@...gle.com,
	Daniel Stone <daniels@...labora.com>, seanpaul@...gle.com,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	linux-kernel@...r.kernel.org, laurent.pinchart@...asonboard.com,
	Gustavo Padovan <gustavo.padovan@...labora.co.uk>,
	John Harrison <John.C.Harrison@...el.com>, m.chehab@...sung.com
Subject: Re: [RFC 0/5] rework fences on struct sync_file

Hi Christian,

2016-06-24 Christian König <christian.koenig@....com>:

> Am 23.06.2016 um 17:29 schrieb Gustavo Padovan:
> > From: Gustavo Padovan <gustavo.padovan@...labora.co.uk>
> > 
> > Hi all,
> > 
> > This is an attempt to improve fence support on Sync File. The basic idea
> > is to have only sync_file->fence and store all fences there, either as
> > normal fences or fence_arrays. That way we can remove some potential
> > duplication when using fence_array with sync_file: the duplication of the array
> > of fences and the duplication of fence_add_callback() for all fences.
> > 
> > Now when creating a new sync_file during the merge process sync_file_set_fence()
> > will set sync_file->fence based on the number of fences for that sync_file. If
> > there is more than one fence a fence_array is created. One important advantage
> > approach is that we only add one fence callback now, no matter how many fences
> > there are in a sync_file - the individual callbacks are added by fence_array.
> > 
> > Two fence ops had to be created to help abstract the difference between handling
> > fences and fences_arrays: .teardown() and .get_fences(). The former run needed
> > on fence_array, and the latter just return a copy of all fences in the fence.
> > I'm not so sure about adding those two, speacially .get_fences(). What do you
> > think?
> 
> Clearly not a good idea to add this a fence ops, cause those are specialized
> functions for only a certain fence implementation (the fence_array).

Are you refering only to .get_fences()?

> 
> What you should do is try to cast the fence in your sync file using
> to_fence_array() and then you can access the fences in the array.

Yes, that seems a better idea I think. The initial idea was to abstract         
the difference as much as possible, but it doesn't seem really worth            
for .get_fences().

	Gustavo