port-evbarm/48117: disklabel(8) and mount_msdos(8) on evbarm don't work with USB pen drives that work on other architectures

[dhgutteridge%sympatico.ca@localhost]

>Number:         48117
>Category:       port-evbarm
>Synopsis:       disklabel(8) and mount_msdos(8) on evbarm don't work with USB 
>pen drives that work on other architectures
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-evbarm-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Aug 13 02:10:00 +0000 2013
>Originator:     David H. Gutteridge
>Release:        6.99.23
>Organization:
>Environment:
(I don't have access to run "uname -a" right now, but it's 6.99.23/evbarm from 
a July 31st releng build.)
>Description:
If I try to mount a USB pen drive with an FAT12 or FAT16 file system
on a Raspberry Pi running 6.99.23/evbarm, the actual partition with
data on it isn't being recognized. The same examples work on other
architectures I've tried (amd64, i386, macppc).

Disklabel output on amd64:

# /dev/rsd1d:
type: SCSI
disk: Store 'n' Go    
label: fictitious
flags: removable
bytes/sector: 512
sectors/track: 32
tracks/cylinder: 16
sectors/cylinder: 512
cylinders: 980
total sectors: 501760
rpm: 3600
interleave: 1
trackskew: 0
cylinderskew: 0
headswitch: 0           # microseconds
track-to-track seek: 0  # microseconds
drivedata: 0 

5 partitions:
#        size    offset     fstype [fsize bsize cpg/sgs]
 d:    501760         0     unused      0     0        # (Cyl.      0 -    979)
 e:    501728        32      MSDOS                     # (Cyl.      0*-    979)

Disklabel output on evbarm:

# /dev/rsd0c:
type: SCSI
disk: Store 'n' Go    
label: fictitious
flags: removable
bytes/sector: 512
sectors/track: 32
tracks/cylinder: 16
sectors/cylinder: 512
cylinders: 980
total sectors: 501760
rpm: 3600
interleave: 1
trackskew: 0
cylinderskew: 0
headswitch: 0           # microseconds
track-to-track seek: 0  # microseconds
drivedata: 0 

3 partitions:
#        size    offset     fstype [fsize bsize cpg/sgs]
 c:    501760         0     unused      0     0        # (Cyl.      0 -    979)

>How-To-Repeat:
Try mounting a USB pen drive with an FAT partition.
>Fix:
None known.