Driver for device behind a PCI-VME bridge

Konstantin Boyanov kkboyanov at
Tue Aug 21 19:49:25 EST 2007

Hi again,

I also work with devices on the VME bus. The approach we took is to map
> all the devices into userspace, and use Xenomai for RT performance. This
> avoids the need to write drivers for all the devices. The RT-performance
> of Xenomai is quite good: the jitter on a timer-interrupt is always less
> than 20usec, even under high load, where standard Linux only achieves
> this in a no load situatieo, under high load standard Linux has a jitter
> of over 10 msec.

Good advice, I will investigate in this direction.

The setup we choose was to have a RT-interrupt handler and a RT IOCTL
> call "WAIT_FOR_INTERRUPT". This is a slightly modified version from the
> Motorola driver (I guess that you also use the Tundra chipset to access
> the VME-bus).

Yes, I do. It is the Tsi148 in fact. I'll be interested to see some sample
code of yours, if it doesn't violate some restrictions ofcourse.

Here you can wait for a specific VME interrupt-level, and
> it returns the vector number. So you can have several applications
> connect to the same VME driver, but all on different levels.

So, if I understand you correctly, you altered the Motorola driver in order
for it to be able to communicate with user spae programms through Xenomai.
Which version of Xenomai ws that? I tried to test Xemonai 2.0 on my setup
but it iterfred somehow with SSH configuration and thats why i dropped it.

Many thanks,
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