Hi Janet,
If you go to http://www.realtimelinux.org/CRAN/examples/ there are some
examples (see README.rtexamples, and get rtexamples.tar.gz)
If you untar this, there is a subdirectory sine_wave. This example
shows direct writes to the video adapter, from user and kernel space.
It works with 2.0 (RTLv1) or 2.2 (RTAI) so you should be able to see how
to do it for either the 2.0 or 2.2 kernels (the mechanism for RTLv2
would be the same). As Dave Schleef sugested, the initialisation in
userspace uses VGA lib, once this is done, the adapter is mapped into
the user's address space and can be directly written.
Note: This example won't work on 2.2 if you have build Linux with frame
buffer support.
Regards, Stuart.
Estabridis, Janet P wrote:
>
> Dave,
> I am doing this from user space right now. I am using fd "/dev/mem" which
> is what Mr. Rubini's book example and he's advice via e-mail was.
>
> What is the difference between "/dev/mem" and "/dev/kmem" ?
>
> I'll try "/dev/kmem" and I'll try and look at the SVGAlib source.
>
> I truely did not think accessing a memory mapped card would be trouble from
> user space and I thought it would be easier until things are working (if you
> can map it). I'll also try it from kernel space if all else fails.
>
> Thanks -
> Janet
>
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