lkml.org 
[lkml]   [2011]   [Dec]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [RFC v2 1/2] dma-buf: Introduce dma buffer sharing mechanism
From
On Mon, Dec 05, 2011 at 04:11:46PM -0600, Rob Clark wrote:
> On Mon, Dec 5, 2011 at 3:23 PM, Daniel Vetter <daniel@ffwll.ch> wrote:
> > On Mon, Dec 05, 2011 at 02:46:47PM -0600, Rob Clark wrote:
> >> I sort of preferred having the DMABUF shim because that lets you pass
> >> a buffer around userspace without the receiving code knowing about a
> >> device specific API.  But the problem I eventually came around to: if
> >> your GL stack (or some other userspace component) is batching up
> >> commands before submission to kernel, the buffers you need to wait for
> >> completion might not even be submitted yet.  So from kernel
> >> perspective they are "ready" for cpu access.  Even though in fact they
> >> are not in a consistent state from rendering perspective.  I don't
> >> really know a sane way to deal with that.  Maybe the approach instead
> >> should be a userspace level API (in libkms/libdrm?) to provide
> >> abstraction for userspace access to buffers rather than dealing with
> >> this at the kernel level.
> >
> > Well, there's a reason GL has an explicit flush and extensions for sync
> > objects. It's to support such scenarios where the driver batches up gpu
> > commands before actually submitting them.
>
> Hmm.. what about other non-GL APIs.. maybe vaapi/vdpau or similar?
> (Or something that I haven't thought of.)

They generally all have a concept of when they've actually commited the
rendering to an X pixmap or egl image. Usually it's rather implicit, e.g.
the driver will submit any outstanding batches before returning from any
calls.
-Daniel
--
Daniel Vetter
Mail: daniel@ffwll.ch
Mobile: +41 (0)79 365 57 48
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2011-12-05 23:35    [W:0.122 / U:3.156 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site