On 28/06/2011 11:35, Martin Kielhorn wrote:
Hi list,
is it possible to synchronise the drawing process to the vsync cycle of
the graphics
card from user level?
Or should I try to modify driver/linux/ogp_skel.c to my needs?
ogp_skel doesn't really do anything. It is just a skeleton of a driver.
I have never tested any of the vblank interrupt generation support. I
think the hardware is wired up, but you'd really have to read the RTL to
see. I guess the ogp_skell example might be useful to see if the
interrupt is being generated? I guess if you do start getting them it
will flood some logging buffer somewhere - it's not a very sensible
program. You should be able to see plug/unplug interrupts with ogp_skel.
I came to the project after the discussions on how this was going to
work, but I was always a bit suspicious that we would need more features
adding to better handle this. At the moment to change the starting
address of the video output you have to reprogram the VC, and the start
address is stored in (at least) two different locations, so there is the
risk of tearing. I suspect that we really need something like a
register that you write to that then becomes the starting address of the
"next" frame. I also suspect that a register that you can read that
"counts" frames would also be interesting / useful.
(A lot of the hardware hasn't been designed to make debugging easy).
MM
I want to have a program that consecutive draws numbers on the
framebuffer, so that
every frame displays the following integer. Then I want to use a camera
to capture these
images.
I had a really hard time when I tried to do this with Nvidia or ATI
cards and I think I still haven't solved it.
Regards, Martin
--
Martin Kielhorn
Randall Division of Cell & Molecular Biophysics
King's College London, New Hunt's House
Guy's Campus, London SE1 1UL, U.K.
tel: +44 (0) 207 848 6519, fax: +44 (0) 207 848 6435
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