To specific questions of the PRU software I would rather defer to one of the experts. Charles S would probably be the person to talk to on this matter.
What I would do in your place however is probably get a recent image. If wheezy ( which I personally prefer - sysv versus systemd init daemon - stock ), then use apt-cache search linux-image, to find the kernel I want. I usually go with the latest 4.x kernel . . . then apt-cache search pru to find the PRU compiler tools.
One thing to be aware of. You do not have to compile your own kernel and create a module to use the PRU. As I am not 100% sure what you’re going to do to achieve your end goal. But the drivers for the pru etc are all there already. All you really need is a software interface to get the data from the PRU, to Linux, and then out ethernet I’m gathering ?
I had / have a similar project but reading CANBus and spitting the data out over ethernet( websockets ). Without creating my own kernel module. Just using the socketCAN library, and a library called “libmongoose”.
I have no hands on with using the PRUs yet. I have done a lot of reading on them. But it seems to reason that a kernel module is not exactly necessary ? I’m thinking from 30,000ft that the pru library set once in Linux, could be used similar to how I used socketCAN. Then write intermediate code between the PRU libraries to something like libmongoose to achieve your goal ? Perhaps through an IPC mechanism ( I’m leaning towards Message Queues but still debating ).
IDK perhaps food for thought ?