[Xen-devel] First post-xenbus-change USB patch

[harry <harry@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx>]

Here's the first snapshot of the USB code after updating to the new
xenbus.

The xenidc code provides a much higher level of abstraction than the new
xenbus code so the changes didn't affect the usb driver much.

I had to put in empty frontend_changed and backend_changed functions
because the new xenbus code segfaults without them.  The USB code
doesn't need them because the entire state machine and all associated
ring/shared page setup is factored out into the xenidc_endpoint object
and the driver code gets connect and disconnect callbacks from the
endpoint instead.

I'd like the otherend_changed entrypoint to be optional please.  This
will also let me remove the MixedCaps XenbusState typename from my
code :-)

I took the opportunity to implement suspend and resume in the frontend
(and the backend to keep the code equivalent) though this is currently
untested.

I did a quick bit of testing and managed to mount the USB key again etc
but had a few problems with module unload and reload.  I think I maybe
got hit by the unregister_watch deadlock then, after I killed the FE
domain, the new xenbus code gave an error message when I tried to unload
and reload the BE.

I think there must have been some stale state in the store which was
confusing the state machine in the new xenbus code.

I'm using this state machine
http://lists.xensource.com/archives/html/xen-devel/2005-10/msg01199.html
in the xenidc endpoint code.  It is designed to be robust against stale
state left in the store and was working nicely for module load and
unload.

There were a couple of small wins for my code: I could use the otherend
and otherend_id fields from the xenbus_device instead of having my own
and I was able to remove the xenbus_gather from the FE since it doesn't
need any configuration parameters other than the otherend and
otherend_id fields.

The BE still needs to read the USB path so I couldn't remove the gather
from the BE.

Thanks for your offer of help BTW.  Just saw it as I'm writing this :-)

Harry.

Attachment: latest-usb-patch.gz
Description: GNU Zip compressed data

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