Re: [Xen-devel] How to decide the xenstore path for a domain

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Sat, 2012-08-25 at 12:15 +0100, Bei Guan wrote:
> Hi,
> 
> 
> Can anyone tell me how to decide the number in the Xenstore key path
> for a DomU's front driver? 
> In Mini-OS, the block front driver write the key-value to
> "device/vbd/768/[ring-ref|event-channelprotocol|...]" according to the
> code mini-os/blkfront.c.
> So why does it use the number "768" in the path here? Can this number
> be another one? For a new DomU's block front driver, how to decide
> this number?

It is the VBD number, as described in docs/misc/vbd-interface.txt. 768
is "3<<8 | 0" per the "Concrete encoding in the VBD interface (in
xenstore)" section.

You (as frontend driver author) don't need to decide it since it is
provided by the toolstack/guest config. You should just process each
sub-directory of "device/vbd" as a separate disk.

Ian.




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