Re: [PATCH 1/4] introduce intel_ring_buffer structure

From: Daniel Vetter <daniel@ffwll.ch>
To: "Zou, Nanhai" <nanhai.zou@intel.com>
Cc: "Anholt, Eric" <eric.anholt@intel.com>,
	Intel GFX <intel-gfx@lists.freedesktop.org>
Subject: Re: [PATCH 1/4] introduce intel_ring_buffer structure
Date: Mon, 17 May 2010 19:42:33 +0200	[thread overview]
Message-ID: <20100517174232.GA3546@viiv.ffwll.ch> (raw)
In-Reply-To: <41EFD7A46E18724CAB128DAD0073348006A62B749A@shsmsx502.ccr.corp.intel.com>

Hi

On Mon, May 17, 2010 at 09:43:02AM +0800, Zou, Nanhai wrote:
> 	You may check how user space works in VAAPI code, if you have an Ironlake system.
> We have install guide at http://intellinuxgraphics.org/h264.html.
> We have some customer requests for H.264 decoding, so we point to an
> early kernel and a similar patch on that page.

I'll try this out. But likely takes a while till I get around - there's
enough other stuff going on to keep me busy.

> Actually no additional synchronize was add to user space, after BSD
> decoding is done, we map the BSD output for media pipe input command
> stream, at this point kernel will wait BSD decoding done before it begin
> media pipe.
> 
> so unprivileged client can not damage GPU with this.
> 
> Though this is not the most efficient way to do the work, 
> 
> One of our optimize plan is to have double ring buffer for H.264
> decoding later, e.g. while BSD is decoding to one buffer, media pipe may
> consume another buffer,
> 
> So media and BSD ring can work in parallel. Once we begin to do that, we
> may need to design a better synchronize method.

Well, that's exactly the problem. You simply can't optimize a kernel
interface once it's in use. And if you try to, your users will get the
pitchforks and scream bloody murder trying to get you ;) So we need to get
these patches right (at least the semantics of the interface) beforehand.

> Thanks
> Zou Nan hai

Yours, Daniel
-- 
Daniel Vetter
Mail: daniel@ffwll.ch
Mobile: +41 (0)79 365 57 48