Re: Where/how to start implementing vertical retrace interrupt interface?

[Will Dyson <will.dyson@gmail.com>]

On 7/2/05, Peter Ronnquist <pronnquist@yahoo.com> wrote:

I've added the dri-devel and xorg mailing lists to the cc: list.

> If I have understood things correctly then X/x.org can
> not provide a flicker free update of the graphics on a
> display since the linux kernel does not provide a way
> to synchronize to the vertical retrace of a display.
> 
> See
> http://lists.freedesktop.org/archives/xdg/2004-August/004561.html

I don't know if that was true at the time it was written, but today
the DRM implements vblank wait for 3 drivers (mga, r128, and radeon).
However, as far as I can tell, none of the X server's 2d  drivers
makes use of it. Perhaps some more work is needed to make the
interface convient for the X server?

If you have a card supported by one of these drivers, you can move on
to getting the X server to use that capability to support vblank
counters in the XSync extension.

http://freedesktop.org/~jg/roadmap.html#mozTocId921013

Then you only need for toolkits (and/or individual apps) to get with
the program and start using using XSync.

> If a person with little previous experience of the
> linux kernel source tree would like to start on such a
> feature then how complicated do you believe it is to
> implement? (days or months of work)
>
> Where in the kernel source is a good place to start
> looking?

linux/drivers/char/drm/  is where the kernel drivers for graphics cards live. 

Here is an overview of the different pieces of the current
drm/dri/xserver graphics puzzle:
http://dri.freedesktop.org/wiki/DriverFiles

-- 
Will Dyson