Re: [Xen-devel] Is there example code and/or documentation for developing a Xen back-end/front-end driver pair?

[Randy Thelen <rthelen@xxxxxxxxxx>]

Anthony Liguori wrote:

> (although it's probably stable enough now to document)
I'm getting that feeling.

> In principle, once you have bring up working, making it work in  
> Xend isn't so bad.  Do you have specific questions or are you just  
> looking for a where to begin?
I see this "orange of a problem" and I'm trying to get my fingernail  
under the orange peel.
It appears that in order to get the front-end to talk to the back- 
end, using the standard xenbus and interface type files I seen in  
blkback/ and blkfront/ driver source code directories, that I need to  
begin in Xend.  So, I'm looking in Xend and I -think- I get most of  
the architecture relevant here.  But, it's not clear to me, yet,  
exactly what Xend asks of the back end driver in order to get the  
system going.
For example, when it's decided that a blk back end will be used,  
blkif.py is run and part of what appears to happen is that the dom0  
blk driver is kicked somehow (!?) and a Python Event is used (in  
DevController.py) with an xswatch() call to wait for the backed to  
startup.  And, it seems that the trigger to observing the startup is  
complete is the back end putting some data into XenStore (into  
statusPath = backpath + '/' + HOTPLUG_STATUS_NODE).
I'm trying to figure out how this aspect of Xend works,  
specifically.  :-)
Any pointers there?  Or, am I way out in the weeds?

-- Randy

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