The ubuntu "-rt" kernel is not compatible with emc.  Only the "-rtai"
kernel is compatible with the precompiled version of emc, and only
"rtai" and "rtlinux" realtime kernels are supported for compiling emc.

The ubuntu "-rt" kernel does not provide the APIs that are used by emc2
for its realtime components and hardware drivers.  One reason that we
have not worked to support "-rt" is because it generally offers lower
realtime performance on the same hardware compared to rtai.

My limited experience with the "-rt" indicates that it might be OK for
"smart hardware" like mesa/ppmc but probably not for "dumb hardware"
like software step generation on the PC parallel port.

I believe that an interested developer with a knowledge of kernel and/or
pthreads programming could write a new implementation of emc's "rtapi"
compatability layer for the Ubuntu Studio "-rt" kernel.  Personally, I
would be happy to consider such a patch for inclusion in the development
version of emc.  You can find some work I did along these lines a year
ago here:
   http://axis.unpy.net/01190912545
however I am not sure that the userspace/pthreads approach is the right
one, because it means that HAL device drivers can't use kernel APIs such
as pci_find_device and ioremap_nocache.  In that case, rtapi would need
a new set of APIs for these tasks, implemented in kernel space with the
kernel APIs and in userspace with some kind of PCI access library.

Jeff

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