Re: [Xen-devel] [PATCH v5 6/8] libxl: introduce libxl__alloc_vdev

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2012-05-04 at 17:46 +0100, Ian Jackson wrote:
> Ian Campbell writes ("Re: [PATCH v5 6/8] libxl: introduce libxl__alloc_vdev"):
> > On Fri, 2012-05-04 at 12:13 +0100, Stefano Stabellini wrote:
> > > Introduce libxl__alloc_vdev: find a spare virtual block device in the
> > > domain passed as argument.
> ...
> > > +    libxl__device_disk_dev_number(blkdev_start, &disk, &part);
> > 
> > If you specify the default blkdev_start in xl as d0 instead of xvda
> > doesn't at least this bit magically become portable to BSD etc too?
> 
> This bit is portable already.  It's specified in terms of the guest
> device name rather than the host device name.  This may be confusing
> but it saves on having a converter for host device names to disk
> numbers.

Right. I think I really should have made this comment on the previous
patch, What I was trying to suggest is that using the Linux specific
"xvda" in the example in the config file and as the default (as patch
5/8 does) is not portable, even though the infrastructure itself is
quite capable of dealing with the portable alternatives -- IOW using
"d0" both in the example and in the actual default would make xl be
automatically portable without other patches (libxl still needs a patch
for the BSD libxl__devid_to_localdev but that's it).

> > Or couldn't it actually be an int and save you parsing at all?
> 
> In general it's surely more friendly to allow the user to specify this
> with a name, like we do with vdevs elsewhere.

That seems reasonable.

Ian.


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