Re: waitforVBlank, how does this even work?

[Eric Sellers <sellers-eric@rogers.com>]

On Wednesday 02 March 2005 12:45, Vladimir Dergachev wrote:
> On Wed, 2 Mar 2005, Jon Smirl wrote:
> > On Wed, 2 Mar 2005 12:15:18 -0500 (EST), Vladimir Dergachev
> >
> > <volodya@mindspring.com> wrote:
> >>> I would find it useful if someone came up with a standard kernel space
> >>> V4L radeon driver instead of the Gatos stuff.
> >>
> >> By "standard" you mean "self-contained", right ?
> >
> > One that doesn't depend on X being there.
> >
> > Can one be build now that just ignores the memory management hooks?
>
> Sure, but you would have to give up using X on that card.
>
> In fact, Eric Sellers has already written such a module that provides V4L
> 1 and 2 support (Eric, please correct me if I got anything wrong..)

You can use my module with or without X 
(right now it only supports the older mach64 cards)

The only problem is there is no way of telling X where 
the capture buffers are. So you might get some corruption on screen when X 
uses that memory and it gets overwritten by a frame and then copied back.

The more memory you have the less you will notice this.
(so if you have a 4 meg card, you might want to keep your resolution and bit 
depth down)

If there was a userspace program that could allocate the end of video memory 
there would be no problem.

Eric


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