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Date:      Mon, 17 Oct 2016 11:34:19 -0700
From:      bob prohaska <fbsd@www.zefox.net>
To:        freebsd-arm@freebsd.org
Subject:   Are all USB ports equivalent?
Message-ID:  <20161017183418.GA43296@www.zefox.net>

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In upgrading stable/11 on one of my RPI2 hosts it seems that /dev/da0 isn't being
created by the kernel. A second machine with the same software has no such problem.
Both are self-hosting, with /usr, /var /tmp and swap on a usb flash drive. Root is
on microSD.

It happens that the USB flash drive holding the outboard filesystems (root is on
microSD for both machines) is in a different slot on the two machines.

The one which boots successfully reports

FreeBSD www.zefox.com 11.0-STABLE FreeBSD 11.0-STABLE #9 r307491: Mon Oct 17 03:01:20 PDT 2016     bob@www.zefox.com:/usr/obj/usr/src/sys/RPI2  arm

and shows
ugen0.6: <SanDisk> at usbus0
umass0 on uhub1
umass0: <SanDisk Extreme, class 0/0, rev 2.10/0.10, addr 6> on usbus0
ugen0.7: <vendor 0x067b> at usbus0
da0 at umass-sim0 bus 0 scbus0 target 0 lun 0
da0: <SanDisk Extreme 0001> Removable Direct Access SPC-4 SCSI device
da0: Serial Number AA010509160727180727
da0: 40.000MB/s transfers
da0: 59836MB (122544516 512 byte sectors)
da0: quirks=0x2<NO_6_BYTE>

The machine which has trouble reports

FreeBSD 11.0-STABLE #1 r307523: Mon Oct 17 09:30:28 PDT 2016
    bob@ns1.zefox.net:/usr/obj/usr/src/sys/RPI2 arm
and reports

ugen0.4: <SanDisk> at usbus0
umass0 on uhub1
umass0: <SanDisk Extreme, class 0/0, rev 2.10/0.10, addr 4> on usbus0
ugen0.5: <FTDI> at usbus0

with no mention of da0.

The clearest difference I can find between the machines is that the
one which creates /dev/da0 has the flash drive on address 6, the one
which fails to create /dev/da0 has the flash drive at address 4. It's
hard to believe that should matter, but it's the only clue found so far.

Rebooting the failed machine with an older kernel results in normal
operation. Svnlite status /usr/src shows no plausible differences in
the source trees.

I'm thoroughly stumped and would be grateful for any hints. 

Thanks for reading, and any ideas,

bob prohaska




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