[Intel-gfx] [PATCH 1/4] introduce intel_ring_buffer structure

[Zou, Nanhai]

>>-----Original Message-----
>>From: Daniel Vetter [mailto:daniel at ffwll.ch]
>>Sent: 2010年5月18日 1:43
>>To: Zou, Nanhai
>>Cc: Owain Ainsworth; Daniel Vetter; Intel GFX; Anholt, Eric
>>Subject: Re: [Intel-gfx] [PATCH 1/4] introduce intel_ring_buffer structure
>>
>>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
>>

Hi,
Since VAAPI will be the only client for this multi ring buffer for a period of time.
We may not have so much pain to optimize both kernel and user space.
This approach touches little user space interface, only 1 new  flag  is added to IOCTL. 
We have new kinds of ring buffer to come in SandyBridge and later chips. Since we are still enabling  SandyBridge. I can not for cast how those rings would be synchronized to each other. 
We may use minimum API to work first.

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