linux-kernel - Re: [PATCH 2/2] dma-buf/fence: add fence

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Date:	Fri, 20 May 2016 11:47:28 -0300
From:	Gustavo Padovan <gustavo@...ovan.org>
To:	Christian König <deathsimple@...afone.de>
Cc:	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	daniel.vetter@...ll.ch
Subject: Re: [PATCH 2/2] dma-buf/fence: add fence_array fences v4

2016-05-20 Christian König <deathsimple@...afone.de>:

> From: Gustavo Padovan <gustavo.padovan@...labora.co.uk>
> 
> struct fence_collection inherits from struct fence and carries a
> collection of fences that needs to be waited together.
> 
> It is useful to translate a sync_file to a fence to remove the complexity
> of dealing with sync_files on DRM drivers. So even if there are many
> fences in the sync_file that needs to waited for a commit to happen,
> they all get added to the fence_collection and passed for DRM use as
> a standard struct fence.
> 
> That means that no changes needed to any driver besides supporting fences.
> 
> fence_collection's fence doesn't belong to any timeline context, so
> fence_is_later() and fence_later() are not meant to be called with
> fence_collections fences.
> 
> v2: Comments by Daniel Vetter:
> 	- merge fence_collection_init() and fence_collection_add()
> 	- only add callbacks at ->enable_signalling()
> 	- remove fence_collection_put()
> 	- check for type on to_fence_collection()
> 	- adjust fence_is_later() and fence_later() to WARN_ON() if they
> 	are used with collection fences.
> 
> v3: - Initialize fence_cb.node at fence init.
> 
>     Comments by Chris Wilson:
> 	- return "unbound" on fence_collection_get_timeline_name()
> 	- don't stop adding callbacks if one fails
> 	- remove redundant !! on fence_collection_enable_signaling()
> 	- remove redundant () on fence_collection_signaled
> 	- use fence_default_wait() instead
> 
> v4 (chk): Rework, simplification and cleanup:
> 	- Drop FENCE_NO_CONTEXT handling, always allocate a context.
> 	- Rename to fence_array.
> 	- Return fixed driver name.
> 	- Register only one callback at a time.
> 	- Document that create function takes ownership of array.

This looks good to me. Dropping NO_CONTEXT was a good idea, also
registering only one callback makes it looks better.

	Gustavo