Re: [Xen-devel] [PATCH v2 1/7] blkif: document how FreeBSD uses the physical-device backend node

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Thu, Feb 25, 2016 at 08:25:12PM +0100, Roger Pau Monne wrote:
> FreeBSD blkback uses the physical-device xenstore node in order to fetch the
> path to the underlying backing storage (either a block device or raw image).
> This node is set by the hotplug scripts.
> 
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> ---
> Cc: Ian Campbell <ian.campbell@xxxxxxxxxx>
> Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> Cc: Jan Beulich <jbeulich@xxxxxxxx>
> Cc: Tim Deegan <tim@xxxxxxx>
> ---
>  xen/include/public/io/blkif.h | 16 ++++++++++------
>  1 file changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/xen/include/public/io/blkif.h b/xen/include/public/io/blkif.h
> index 99f0326..9a5baa4 100644
> --- a/xen/include/public/io/blkif.h
> +++ b/xen/include/public/io/blkif.h
> @@ -89,14 +89,18 @@
>   *      Values:         string
>   *
>   *      A free formatted string providing sufficient information for the
> - *      backend driver to open the backing device.  (e.g. the path to the
> - *      file or block device representing the backing store.)
> + *      hotplug script to attach the device and provide a suitable
> + *      handler (ie: a block device) for blkback to use.
>   *
> - * physical-device
> - *      Values:         "MAJOR:MINOR"
> + * physical-device:
> + *      Values:         OS specific
>   *
> - *      MAJOR and MINOR are the major number and minor number of the
> - *      backing device respectively.
> + *      A free formatted string that contains the OS specific path to the
> + *      backing device for this blkback instance.
> + *
> + *      Linux and NetBSD encode the block device major and minor numbers 
> using
> + *      the following printf format: "%x:%x", while FreeBSD places the path 
> to
> + *      the file or device in the filesystem.

I think this is a sensible approach FWIW.

Wei.

>   *
>   * type
>   *      Values:         "file", "phy", "tap"
> -- 
> 2.5.4 (Apple Git-61)
> 
> 
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