newfs_udf(8) and wedges

[tlaronde%polynum.com@localhost]

Context: in a previous thread, I had suggested that UDF was a way to
share a filesystem (in my case via an USB connected disk---umass) with,
at least Windows (probably works with Mac too and others, due to the
nature of UDF, but haven't tested).

The trick is to use a GPT header with a sole UDF partition (but,
apparently, from tests, the partition has to start at offset 2048 
_sectors_ for Windows).

I had GPT'ed and formatted under Windows and NetBSD was able to read
using mount_udf(8) and the wedge.

The remaining has been attempted on 6.1.5.

I tried the reverse: setting everything on NetBSD, but it fails:

1) If I can create a GPT (need to force and possibly even to destroy
first to have sensible results) and then add a partition, I was then
unable to dkctl(8) addwedge: I needed to disconnect the disk and
reconnect so that the automatic wedge creation happens ;

2) newfs_udf(8) is using DIOCGDINFO and DISKPART that is relies AFAIU on
disklabel and is unable to deal with wedges. Trying to fake a disklabel
as a workaround lead to disaster.

Is there somewhere documentation or a code canonical example to update
an utility for wedge support?

-- 
        Thierry Laronde <tlaronde +AT+ polynum +dot+ com>
                     http://www.kergis.com/
                     http://www.arts-po.fr/
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