Re: [virtio] [OASIS Issue Tracker] Issue Comment Edited: (VIRTIO-30) allow required features

OASIS Issues Tracker <> writes:
>     [ http://tools.oasis-open.org/issues/browse/VIRTIO-30?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=34614#action_34614 ] 
>
> Michael Tsirkin edited comment on VIRTIO-30 at 9/12/13 4:10 PM:
> ----------------------------------------------------------------
>
> a similar issue if some features or device configuration
> field values are mutually exclusive.
> we would want a way for device to report to driver
> that it's trying to create an inconsistent configuration.
>
>
>       was (Author: mstsirkin):
>     a similar issue if some features are mutually exclusive.
> we would want a way for device to report to driver
> that it's trying to create an inconsistent configuration.

Also, a device may choose not to be completely backwards compatible and
it would be nice to give the guest a way of knowing that (eg. may only
support event indexes).

However, the reason a device would do this is to keep it simple.  Thus
adding a new mechanism to identify this problem may make it worse by
adding complexity and over-engineering, for very little benefit.

As to feature dependencies, there are many ways a driver can be flawed,
and this is probably one of the lesser ones.  The spec should clearly
identify dependent features, though.

I created VIRTIO-33 for the documentation issue, which we should do
anyway.

Cheers,
Rusty.