[Intel-gfx] [PATCH 2/3] drm/i915: add syncobj timeline support

[Chris Wilson]

Quoting Lionel Landwerlin (2020-07-31 14:45:52)
> Introduces a new parameters to execbuf so that we can specify syncobj
> handles as well as timeline points.
> 
> v2: Reuse i915_user_extension_fn
> 
> v3: Check that the chained extension is only present once (Chris)
> 
> v4: Check that dma_fence_chain_find_seqno returns a non NULL fence (Lionel)
> 
> v5: Use BIT_ULL (Chris)
> 
> v6: Fix issue with already signaled timeline points,
>     dma_fence_chain_find_seqno() setting fence to NULL (Chris)
> 
> v7: Report ENOENT with invalid syncobj handle (Lionel)
> 
> v8: Check for out of order timeline point insertion (Chris)
> 
> v9: After explanations on
>     https://lists.freedesktop.org/archives/dri-devel/2019-August/229287.html
>     drop the ordering check from v8 (Lionel)
> 
> v10: Set first extension enum item to 1 (Jason)

The other unaddressed issue here is that we do not need to arbitrarily
limit the caller to only a single extension. The code to handle multiple
invocations is actually smaller...
-Chris