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Re: [libvirt] [PATCH] startupPolicy: Change event argument



On 10/26/2011 05:30 AM, Daniel P. Berrange wrote:
The device aliases are not intended to be limited to just QEMU. The
intention when adding device aliases was to have a standard way to
uniquely refer to a particular device, no matter what type of device
it is. Previously you had to use disk targets, net MAC addrs, serial
port numbers, etc, etc, and some device types didn't even have any
good unique attribute. With device alias, we have a way to provide
a standard identifer for any type of device. While other drivers
may not use this ability yet, there's nothing preventing them from
doing so.

I guess I can live with devAlias on output, if there were an easy way to map from target to devAlias, and also to map from devAlias to target. Also, it would be nice if functions that take device names and/or device paths on input could also be taught to take devAlias on input as another synonym.

In particular, I'm thinking of my recent work in commits 88a993b and 89b6284, where I taught disk snapshots, block peek, and getBlockInfo to all operate on target name or disk path as synonyms. Making those functions also operate on device aliases, as well as making 'virsh domblklist' capable of outputting the devAlias that corresponds to each disk, will make it easier to go between any of the three namespaces (where two are under the control of the xml).

But your argument that blk io error events already use devAlias is pretty convincing. I guess even if we don't have full transparency between the namespaces yet, that consistency argues that both disk-related events should be using the same data. So I think the best plan forward is for this patch to keep devAlias after all (it needs documentation, but it reduces the number of other places to patch), and then later add a patch (series) that makes it easier to convert between aliases and target names.

--
Eric Blake   eblake redhat com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org


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