[Xen-devel] Writing custom Xen backend/frontend driver example

[Roderick Colenbrander <thunderbird2k@xxxxxxxxx>]

Hi all,

I'm trying to write a Xen backend/frontend Linux driver for a custom
device, but I'm having some issues bringing up the frontend and the
backend. For the record I'm using Xen 4.0.1 using a Linux kernel from
the xen/stable-2.6.32.x git repository.

I started by recreating the 'deviceback / devicefront' sample
documented on the wiki at
http://wiki.xensource.com/xenwiki/XenIntro#head-e2e4a234896aa188a9addd5e326e818265ba2fea.
The drivers compile properly and load properly (though I had to set
the module license to GPL to get rid of missing symbols). The sample
contains a script to bring up the backend/frontend by writing certain
keys to xenstore. Executing the backend script triggers the 'probe'
call in the backend driver, but when I execute the frontend script it
doesn't seem to trigger the 'probe' call in the frontend driver.

Is this example still supposed to work on recent Xen / Linux kernel
versions? I have the feeling something changed which is not yet in the
example. At a quick glance other Linux drivers look more or less
similar (though they implement some extra xenbus methods to handle
XenbusState changes). What I did notice was that other pv-ops drivers
have extra keys in the xenstore as shown by xenstore-ls. Is this were
some things changed? I tried to look at the xend python scripts, but
with limited xen hacking experience it is hard to judge what's
relevant.

Regards,
Roderick Colenbrander

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