What kind of situation trigger the alloc_surface & free_surface function in video.c (video-driver)

[Cui, Hunk]

Hi, Alex,
	Many thanks for your hints, about the xawtv, only know it is a television viewer-X11 application, I will try to it, any other info, I will reform to you. :)

Thanks,
Hunk Cui 

> -----Original Message-----
> From: Alex Deucher [mailto:alexdeucher at gmail.com]
> Sent: Thursday, August 12, 2010 12:29 AM
> To: Adam Jackson
> Cc: Cui, Hunk; xorg-driver-geode at lists.x.org; xorg-devel at lists.x.org
> Subject: Re: What kind of situation trigger the alloc_surface & free_surface
> function in video.c (video-driver)
> 
> On Wed, Aug 11, 2010 at 10:26 AM, Adam Jackson <ajax at nwnk.net> wrote:
> > On Wed, 2010-08-11 at 10:24 +0800, Cui, Hunk wrote:
> >> Hi, guys,
> >>       Now I am researching about allocate the video overlay memory,
> >> some confuse to inquire.
> >>       In xf86-video-geode -> lx_video.c -> LXInitOffscreenImages:
> >>               alloc_surface = LXAllocateSurface;
> >>               free_surface  = LXFreeSurface;
> >>
> >>       In xf86-video-ati         -> radeon_video.c ->
> >> RADEONInitOffscreenImages:
> >>               alloc_surface = RADEONAllocateSurface;
> >>               free_surface  = RADEONFreeSurface;
> >>
> >>       Inquire: what kind of situation trigger above functions? What
> >> are the mainly effect?
> >
> > The answer appears to be: nothing.  The alloc_surface hook is never
> > called from the core X server.  Which does sort of make me wonder what
> > people thought they were writing when they wrote them...
> >
> > I suspect the intent was to allow XV to offscreen surfaces.
> 
> IIRC, these used to be used by the v4l ddx to stream directly to
> another Xv adapter, or something like that.  I think xawtv used to use
> it back in the day.
> 
> Alex