Re: [Xen-devel] [PATCH 2 of 5] blkif.h: Provide more complete documentation of the blkif interface

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Justin T. Gibbs writes ("Re: [Xen-devel] [PATCH 2 of 5] blkif.h: Provide more 
complete documentation of the blkif interface"):
> On Feb 7, 2012, at 10:51 AM, Ian Jackson wrote:
> > Justin T. Gibbs writes ("[Xen-devel] [PATCH 2 of 5] blkif.h: Provide more 
> > complete documentation of the blkif interface"):
> >> + * params
> >> + *      Values:         string
> > 
> > this is not intended for use by guests and they should not look at it.
> 
> Guests can export back-end devices.  Here at Spectra we do this all the
> time. :-)

Sorry, I meant, not intended for use by frontends.  I was using
"guest" as a shorthand for that.

> It would be hard to implement a blkback driver without this information.
> The comment at the top of your email implies you're okay with it being
> in this file, but that I should mark "local-end use only" nodes?

Certainly I think it would be good to document this somewhere and here
is as good as any.

> >> + * virtual-device
> >> + *      Values:         <uint16_t> (XEN_*_MAJOR << 8 | Minor)
> > 
> > This should be a reference to docs/misc/vbd-interface.txt.  But isn't
> > this also encoded in the device path in xenstore ?
> 
> It would appear so.  Should this path naming convention be mandated by
> this file?  Since "virtual-device" exists, it seems that front-ends should
> read it, not parse the path, to determine this information.

Do we know what current frontends actually do ?

Ian.

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