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Re: [Xen-devel] Trans.: Device drivers and Xend


  First thanks for your answer and your encouragements.

So first, why I am using Xen 2.0.7 instead of Xen 3.x, whereas things I want
would be easier to implement with the Xen3 API, is because I need a XenoLinux
2.4 kernel. And, if I am right, Xen3 currently support Linux 2.6 but not 2.4.
And... in fact it is the only reason.

Now, what I want to be implemented in my driver : when the front-end
(corresponding to my driver) is loaded in a domU, I need an event channel to be
set up and a shared memory page. By this way the front-end will communicate data
to the back-end, by writing data in the shared memory page and sending a
notification event. Something very classical. Of course, several front-end
could connect to the same back-end.

So (I think) what I need (with Xen2) is to add in Xend the management of my new
driver, by adding the right python script, like mydevif.py. I need to define my
control message, like CMSG_MYDEV_CONNECT, to add them to
/usr/lib/python/xend/server/messages.py. By this way when a front-end starts,
it sends a CMSG_MYDEV_CONNECT via the control interface, and Xend creates the
event channel between the back and front end and set up a shared memory page.

If I am right above, I just need to understand where to add the needed code in
Xend, how to add a new device type, which are the methods / class to implement,
..., which seems difficult to me, as Xend is not well documented. Also if I
want this virtual driver to be set up juste for particular guests, I need to
modify the configuration script for domain and so xm, to add a new parameter,
like mydev = 0 | 1. But once again, as the process of adding a new device type
in Xend is not described, it seems difficult to me.

Of course, it seems that such things are really easier to implement in Xen3.x,
as I saw in some examples. But I do really need a Linux 2.4 kernel,

So what I wondered first if is I am right on the above explanations, and if some
body can tell me the tips I need about Xend.

Thanks again.

PS : If nobody can help me and that I don't succeed by myself in adding what I
want in Xend, I will try with Xen3, but I really need a 2.4 Linux kernel (for

Selon Mark Williamson <mark.williamson@xxxxxxxxxxxx>:

> Hi there,
> It's great that you're working on Xen.  Sounds like you're making good
> progress.
> However, do you really have to use Xen 2.0.7?  It's not really supported any
> more - the 3.x series gets all the attention these days.  The main difference
> between the two from your point of view is probably in the control interface.
> The Xend parts of the code are concerned with sending control messages to
> domains in the right sequence so that their drivers may handshake and set up
> shared memory / event channel.  In Xen 3.x, the Xend components of a split
> driver are very different and *much* simpler, but you need to use XenStore in
> the devices.
> Could you give any more detail about your device drivers?  What requirements
> do they have? (shared memory pages, event channels, other metadata etc...)
> Cheers,
> Mark
> On Wednesday 06 September 2006 15:10, nicko.koinkoin@xxxxxxx wrote:
> > Hi everybody
> >
> > I am currently writting a split device driver for a custom device.
> >
> > I have understood the way it works, I wrote the code (kernel module) but
> > currently it is static (i.e. port number) because I am not using Xend.
> >
> > And I want to use it, but I don't know how to add a new device type in
> > Xend, i.e. which files are needed, ... I looked at blkif.py and netif.py, I
> > know I have to write such a script for my new device, but what are the
> > classes/object that must be present, the same for the methods ?
> >
> > Also how do I set up a virtual custom device for the domains
> > (XendDomainInfo.py ?) ?
> >
> > In fact I search for a manual describing in details Xend, like a HowTo Xend
> > device drivers, what I didn't find in the ML. I am using xen-2.0.7, so I
> > think there is no XenBus and XenStore.
> >
> > If somebody can give me advice.
> >
> > Thanks.
> >
> >
> >
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-devel
> --
> Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
> Mark: To answer a question with a question: What use is a skateboard?
> Dave: Skateboards have wheels.
> Mark: My wheel has a wheel!


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