On 28 Nov 2007 06:19:39 +0100, Soeren Sandmann <[EMAIL PROTECTED]> wrote:
>
> "Stephane Marchesin" <[EMAIL PROTECTED]> writes:
>
> > I fail to see how this works with a lockless design. How do you ensure
> the X
> > server doesn't change cliprects between the time it has written those in
> the
> > shared ring buffer and the time the DRI client picks them up and has the
> > command fired and actually executed ? Do you lock out the server during
> that
> > time ?
>
> The scheme I have been advocating is this:
>
> - A new extension is added to the X server, with a
> PixmapFromBufferObject request.
>
> - Clients render into a private back buffer object, for which they
> used the new extension to generate a pixmap.
>
> - When a client wishes to copy something to the frontbuffer (for
> whatever reason - glXSwapBuffers(), glCopyPixels(), etc), it uses
> plain old XCopyArea() with the generated pixmap. The X server is
> then responsible for any clipping necessary.
>
> This scheme puts all clip list management in the X server. No
> cliprects in shared memory or in the kernel would be required. And no
> locking is required since the X server is already processing requests
> in sequence.
Yes, that is the idea I want to do for nvidia hardware.
Although I'm not sure if we can/want to implement it in term of X primitives
or a new X extension.
To synchronize with vblank, a new SYNC counter is introduced that
> records the number of vblanks since some time in the past. The clients
> can then issue SyncAwait requests before any copy they want
> synchronized with vblank. This allows the client to do useful
> processing while it waits, which I don't believe is the case now.
Since we can put a "wait until vblank on crtc #X" command to a fifo on
nvidia hardware, the vblank issue is non-existent for us. We get precise
vblank without CPU intervention.
Stephane
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