John Stultz | 28 Feb 03:14 2013

[RFD] Proposal for merging Android sync driver in staging

I'd like to get a discussion going about submitting the Android sync 
driver to staging.

I know there is currently some very similar work going on with the 
dmabuf-fences, and rather then both approaches being worked out 
individually on their own, I suspect there could be better collaboration 
around this effort.

So my proposal is that we merge the Android sync driver into staging.

In my mind, this has the following benefits:
1) It allows other drivers that depend on the sync interface to also be 
submitted to staging, rather then forcing those drivers to be hidden 
away in various out of tree git repos, location unknown.

2) It would provide a baseline view to the upstream community of the 
interface Android is using, providing  a real-world, active use case of 
the functionality.

Once the sync driver is in staging, if the dmabuf-fences work is fully 
sufficient to replace the Android sync driver, we should be able to 
whittle down the sync driver until its just a interface shim (and at 
which point efforts can be made to convert Android userland over to 
dmabuf-fences).

However, if the dmabuf-fences work is not fully sufficient to replace 
the android sync driver, we should be able to at least to whittle down 
the driver to those specific differences, which would provide a concrete 
example of where the dmabuf-fences, or other work may need to be 
expanded, or if maybe the sync driver is the better approach.
(Continue reading)

Greg KH | 28 Feb 03:32 2013

Re: [RFD] Proposal for merging Android sync driver in staging

On Wed, Feb 27, 2013 at 06:14:24PM -0800, John Stultz wrote:
> I'd like to get a discussion going about submitting the Android sync
> driver to staging.
> 
> I know there is currently some very similar work going on with the
> dmabuf-fences, and rather then both approaches being worked out
> individually on their own, I suspect there could be better
> collaboration around this effort.
> 
> So my proposal is that we merge the Android sync driver into staging.
> 
> In my mind, this has the following benefits:
> 1) It allows other drivers that depend on the sync interface to also
> be submitted to staging, rather then forcing those drivers to be
> hidden away in various out of tree git repos, location unknown.
> 
> 2) It would provide a baseline view to the upstream community of the
> interface Android is using, providing  a real-world, active use case
> of the functionality.
> 
> Once the sync driver is in staging, if the dmabuf-fences work is
> fully sufficient to replace the Android sync driver, we should be
> able to whittle down the sync driver until its just a interface shim
> (and at which point efforts can be made to convert Android userland
> over to dmabuf-fences).

Sounds like a good plan to me.

> I've gone through the Android tree and reworked the sync driver to
> live in staging, while still preserving the full patch
(Continue reading)

John Stultz | 28 Feb 19:28 2013

Re: [RFD] Proposal for merging Android sync driver in staging

On 02/27/2013 06:32 PM, Greg KH wrote:
> On Wed, Feb 27, 2013 at 06:14:24PM -0800, John Stultz wrote:
>> I'd like to get a discussion going about submitting the Android sync
>> driver to staging.
>>
>> I know there is currently some very similar work going on with the
>> dmabuf-fences, and rather then both approaches being worked out
>> individually on their own, I suspect there could be better
>> collaboration around this effort.
>>
>> So my proposal is that we merge the Android sync driver into staging.
>>
>> In my mind, this has the following benefits:
>> 1) It allows other drivers that depend on the sync interface to also
>> be submitted to staging, rather then forcing those drivers to be
>> hidden away in various out of tree git repos, location unknown.
>>
>> 2) It would provide a baseline view to the upstream community of the
>> interface Android is using, providing  a real-world, active use case
>> of the functionality.
>>
>> Once the sync driver is in staging, if the dmabuf-fences work is
>> fully sufficient to replace the Android sync driver, we should be
>> able to whittle down the sync driver until its just a interface shim
>> (and at which point efforts can be made to convert Android userland
>> over to dmabuf-fences).
> Sounds like a good plan to me.
>
>> I've gone through the Android tree and reworked the sync driver to
>> live in staging, while still preserving the full patch
(Continue reading)

Erik Gilling | 28 Feb 04:03 2013

Re: [RFD] Proposal for merging Android sync driver in staging

On Wed, Feb 27, 2013 at 6:14 PM, John Stultz <john.stultz <at> linaro.org> wrote:
> Also note: I've done this so far without any feedback from the Android devs
> (despite my reaching out to Erik a few times recently), so if they object to
> pushing it to staging, in deference to it being their code I'll back off,
> even though I do think it would be good to have the code get more visibility
> upstream in staging. I don't mean to step on anyone's toes. :)

Yeah, sorry about that.  I kept meaning to get back to you but kept
getting distracted.  A little background on the patches:

In Honeycomb where we introduced the Hardware Composer HAL.  This is a
userspace layer that allows composition acceleration on a per platform
basis.  Different SoC vendors have implemented this using overlays, 2d
blitters, a combinations of both, or other clever/disgusting means.
Along with the HWC we consolidated a lot of our camera and media
pipeline to allow their input to be fed into the GPU or
display(overlay.)  In order to exploit parallelism the the graphics
pipeline, this introduced lots of implicit synchronization
dependancies.  After a couple years of working with many different SoC
vendors, we found that it was really difficult to communicate our
system's expectations of the implicit contract and it was difficult
for the SoC vendors to properly implement the implicit contract in
each of their IP blocks (display, gpu, camera, video codecs).  It was
also incredibly difficult to debug when problems/deadlocks arose.

In an effort to clean up the situation we decided to create set of
simple synchronization primitives and have our compositor
(SurfaceFlinger) manage the synchronization contract explicitly.  We
designed these primitives so that they can be passed across processes
(much like ion/dma_buf handles), can be backed by hardware
(Continue reading)


Gmane