port-macppc/52869: Kernel unable to enumerate boot device when booting from a USB flash disk (sd(4))

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>Number:         52869
>Category:       port-macppc
>Synopsis:       Kernel unable to enumerate boot device when booting from a USB flash disk (sd(4))
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-macppc-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Dec 27 21:55:00 +0000 2017
>Originator:     Sevan Janiyan
>Release:        NetBSD-8
>Organization:
>Environment:
>Description:
I have a IDE disk less PowerBook5,2 which I boot from a USB flash disk (attached to a sd(4) device).
The kernel is unable to enumerate the boot device correctly and so pause to ask for the root disk, dump device, init before continuing.

I have the following changes made to openfirmware:
boot-device is set to usb0/disk@1:2,\ofwboot.xcf
boot-file is blank
boot-command is set to ." hello" cr " screen" output

I boot the system, run probe-usb proceeded by boot & the system is happy to run the boot loader from a HFS partition of the flash disk & run the kernel from the UFS partition.

>How-To-Repeat:

>Fix: