port-amd64/51216: Can't create wedges on a large (3TB) disk, gpt is ok but dkctl gives an error message

[m33%tok715.net@localhost]

>Number:         51216
>Category:       port-amd64
>Synopsis:       Can't create wedges on a large (3TB) disk, gpt is ok but dkctl gives an error message
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    port-amd64-maintainer
>State:          open
>Class:          support
>Submitter-Id:   net
>Arrival-Date:   Sat Jun 04 22:50:00 +0000 2016
>Originator:     ML
>Release:        7.0.1
>Organization:
>Environment:
NetBSD nxxxxt 7.0.1 NetBSD 7.0.1 (GENERIC.201605221355Z) amd64

>Description:
[ Can't create wedges on a 3TB disk, dkctl error message ]


I follow this tutorial : https://wiki.netbsd.org/users/mlelstv/using-large-disks/ with the GPT + Wedges solution to partition a large disk.

Note: This disk is brand new and functional. 

dmesg output:
wd1 at atabus3 drive 0
wd1: <WDC WD30PURX-64P6ZY0>
wd1: drive supports 16-sector PIO transfers, LBA48 addressing
wd1: 2794 GB, 5814021 cyl, 16 head, 63 sec, 512 bytes/sect x 5860533168 sectors
wd1: drive supports PIO mode 4, DMA mode 2, Ultra-DMA mode 6 (Ultra/133)
wd1(ahcisata0:1:0): using PIO mode 4, DMA mode 2, Ultra-DMA mode 6 (Ultra/133) (using DMA)


This is how I get there:

# dd if=/dev/zero of=/dev/wd1 bs=1m count=10
10+0 records in
10+0 records out
10485760 bytes transferred in 0.025 secs (419430400 bytes/sec)

# gpt show wd1
  start   size  index  contents
      0  20480         

# gpt create wd1

# gpt show wd1
  start   size  index  contents
      0      1         PMBR
      1      1         Pri GPT header
      2     32         Pri GPT table
     34  20413         
  20447     32         Sec GPT table
  20479      1         Sec GPT header

# gpt add -a 32k -l wdc3twdg -t ffs wd1
Partition 1 added, use:
        dkctl wd1 addwedge <wedgename> 64 20352 <type>
to create a wedge for it

# gpt show wd1
  start   size  index  contents
      0      1         PMBR
      1      1         Pri GPT header
      2     32         Pri GPT table
     34     30         
     64  20352      1  GPT part - NetBSD FFSv1/FFSv2
  20416     31         
  20447     32         Sec GPT table
  20479      1         Sec GPT header

<reboot to reload all this stuff>

# gpt show wd1
  start   size  index  contents
      0      1         PMBR
      1      1         Pri GPT header
      2     32         Pri GPT table
     34     30         
     64  20352      1  GPT part - NetBSD FFSv1/FFSv2
  20416     31         
  20447     32         Sec GPT table
  20479      1         Sec GPT header

# dkctl wd1 addwedge wdgwdc3t 64 20352 ffs
dkctl: /dev/rwd1: addwedge: Inappropriate ioctl for device


Find the dkctl ktruss trace : http://pastebin.com/sqe1G5jB

Am I missing something ?
>How-To-Repeat:
dd zero on the fist megabyte of wd1
reboot
start again with gpt
fail at dkctl wd1 makedeges
>Fix:
Workaround: disklabel and force huge size partition. 
I don't like it much.