Dario Dallefrate wrote:
Dear Rtai developers,
I'm looking for suggestions regarding the use of arcnet devices in a
rtai environment.
Linux kernel 2.4 and 2.6 provide drivers for such devices but I wonder
if they are suitable for hard RT.
Specifically, I would use Arcnet in raw mode sending custom messages to
a controller trough a dedicated network with just two nodes
Is there any drivers available for rtai? Is rtnet suitable for arcnet?
I know almost nothing about arcnet, but from what I quickly grabbed from
the Linux sources it seems that it is "only" some further network driver
that should be registrable with the existing RTnet core.
For this purpose you would have to port the required modules from Linux
to RTnet following the existing porting hints for network drivers (see
Documentation directory). One critical point might be the way buffer are
handled by arcnet devices. RTnet provides a deterministic pooling
mechanism to pre-allocate required realtime skbs (rtskbs) of fixed size
(so far the maximum Ethernet packet size + the largest overhead of the
available drivers = 1544 bytes). Don't know what packet sizes can occure
on arcnet, you may have to adapt this value (RTSKB_SIZE).
Further topics might be arcnet-specific configuration of the network
adapters. RTnet comes with an infrastructure for this, but it may be
required to extend it in case arcnet has additional requirements (so far
RTnet is Ethernet-oriented).
Feel free to suggest/discuss extensions or modifications required for
RTnet to support arcnet, preferably on the rtnet-developer list. We will
try to help explaining the internal structure where questions arise. And
we would be very happy to welcome another transport media in the RTnet
project (note that Ethernet-over-FireWire is on its way to RTnet
integration in a similar manner)!
Jan
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