vnd geometry

[Patrick Welche <prlw1%cam.ac.uk@localhost>]

Having enabled DIOCGDISKINFO support for vnd, I am surprised that the
numbers don't add up - the plist and the disklabel differ:

$ ./labeltest vnd0a
size of /dev/vnd0a: 12582912 bytes
sectors-per-unit: 24576
sector-size: 512 bytes

from label:
size of /dev/vnd0a: 12761600 bytes
d_secperunit: 24925
d_secsize: 512 bytes
a: 24925 (+0)
b: 0 (+0)
c: 0 (+0)
d: 24925 (+0)

The first few lines of output are the plist. For a real disk, they match:

$ ./labeltest rwd0a
size of /dev/rwd0a: 500107862016 bytes
sectors-per-unit: 976773168
sector-size: 512 bytes

from label:
size of /dev/rwd0a: 500107862016 bytes
...


One oddity while perusing the code is:

        /*
         * Use pseudo-geometry specified.  If none was provided,
         * use "standard" Adaptec fictitious geometry.
         */
        if (vio->vnd_flags & VNDIOF_HASGEOM) {
 
            memcpy(&vnd->sc_geom, &vio->vnd_geom,
                sizeof(vio->vnd_geom));

How can VNDIOF_HASGEOM ever be set?

Any thoughts on how this is meant to work?


Cheers,

Patrick