Re: [Xen-devel] [PATCH 10/14] docs: update xl-disk-configuration.txt to describe new syntax

[Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>]

On Wed, 2011-05-18 at 11:31 +0100, Ian Jackson wrote:
> 
> > > +where each diskspec is in this form:
> > > +
> > > +   [<key>=<value>|flag]*,
> > > +     [<target>, [<format>, [<vdev>, [<access>]]]],
> > > +     [<key>=<value>]*,
> > > +     [target=<target>]
> > 
> > The actual meaning of this is pretty opaque. The paragraphs following
> > "More formally" does a pretty good job of describing it but I still have
> > a few questions/misunderstandings.
> 
> Do you think I should get rid of this template ? 

I think it would be ok if you correct the * placements etc. Having some
sort of (semi-)formal syntax declaration in addition to the wordy
description is useful IMHO.

Would the syntax be clearer as a BNF style thing rather than a regexp-y
thing? e.g. this would allow "[<target>, [<format>, [<vdev>,
[<access>]]]]," to be declared as "POSITIONAL_PARAMETERS := ..." making
the syntax a little more self-documenting and "KEY := ..." could be
defined with reference to the relevant following sections etc.

Should the second "<key>=<value>" usage also have a "|flag"?

I presume "key" can also == "target" and can be the non-ultimate key so
long as the value does not contain any problematic characters. In this
case the explicit target= needs to be marked as optional.

Ian.


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