[libvirt] PATCH: Allow xen bus type for disks in QEMU driver

[Jim Meyering]

"Daniel P. Berrange" <berrange at redhat.com> wrote:
> With the recent work to support -drive arg, the QEMU driver now supports
> many types of bus for disks attached to VMs - ide, scsi, virtio. This patches
> adds another type 'xen' for the Xen blkfront driver.
...
> diff -r f6b47c9986b9 src/util.c
> --- a/src/util.c	Sat May 10 12:57:20 2008 -0400
> +++ b/src/util.c	Sat May 10 12:57:46 2008 -0400
> @@ -779,23 +779,17 @@
>      const char *ptr = NULL;
>      int idx = 0;
>
> -    if (strlen(name) < 3)
> +    if (!STRPREFIX(name, "fd") &&
> +        !STRPREFIX(name, "hd") &&
> +        !STRPREFIX(name, "vd") &&
> +        !STRPREFIX(name, "sd") &&
> +        !STRPREFIX(name, "xvd"))
>          return -1;
>
> -    switch (*name) {
> -        case 'f':
> -        case 'h':
> -        case 'v':
> -        case 's':
> -            break;
> -        default:
> -            return 0;
> -    }
> -
> -    if (*(name + 1) != 'd')
> -        return -1;
> -
> -    ptr = name+2;
> +    if (STRPREFIX(name, "xvd"))
> +        ptr = name+3;
> +    else
> +        ptr = name+2;

Looks fine.
The only change I'd be tempted to make would be to
iterate over the prefixes, so that the fact "xvd" is
a different length isn't handled separately:

    const char *ptr = NULL;
    static char const* const drive_prefix[] = {"fd", "hd", "vd", "sd", "xvd"};
    unsigned int i;
    for (i = 0; i < ARRAY_CARDINALITY(drive_prefix); i++)
        if (STRPREFIX(name, drive_prefix[i]) {
            ptr = name + strlen(drive_prefix[i]);
            break;
        }

    if (!ptr)
        return -1;