180 lines
7.3 KiB
Groff
180 lines
7.3 KiB
Groff
.\"
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.\"
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.\" Copyright (c) 1997 Joerg Wunsch
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.\"
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.\"
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.\" " (emacs disconfusion)
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.Dd December 21, 1998
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.Dt RDP 4 i386
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.Os
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.Sh NAME
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.Nm rdp
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.Nd Ethernet driver for RealTek RTL 8002 pocket ethernet
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.Sh SYNOPSIS
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.Cd "device rdp0 at isa? port 0x378 irq 7"
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.Cd "device rdp0 at isa? port 0x378 irq 7 flags 0x2"
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.Sh DESCRIPTION
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The
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.Nm
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device driver supports RealTek RTL 8002-based pocket ethernet adapters,
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connected to a standard parallel port.
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.Pp
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These adapters seem to belong to the cheaper choices among pocket
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ethernet adapters. The RTL 8002 is the central part, containing an
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interface to BNC and UTP (10 Mbit/s) media, as well as a host
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interface that is designed to talk to standard parallel printer
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adapters. For the full ethernet adapter to work, it is completed by
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an external RAM used as the Tx and Rx packet buffer (16 K x 4 for the
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RTL 8002), and an EEPROM to hold the assigned ethernet hardware
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address. For the RTL 8002, the EEPROM can be either a standard 93C46
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serial EEPROM (which seems to be a common choice), or a 74S288
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parallel one. The latter variant needs the device configuration flag
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0x1 in order to work.
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.Pp
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Since standard printer adapters seem to vary wildly among their timing
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requirements, there are currently two possible choices for the way
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data are being exchanged between the pocket ethernet adapter and the
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printer interface. The default is the fastest mode the RTL 8002
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supports. If the printer adapter to use is particularly slow (which
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can be noticed by watching the ethernet wire for crippled packets, or
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by not seeing correctly received packets), the configuration flag 0x2
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can be set in order to throttle down the
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.Nm
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driver. Note that in fast mode, the data rate is asymmetric, sending
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is a little faster (up to two times) than receiving. Rates like 150
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KB/s for sending and 80 KB/s for receiving are common. For slow mode,
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both rates are about the same, and in the range of 50 KB/s through 70
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KB/s. As always, your mileage may vary.
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.Pp
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In case the adapter isn't recognized at boot-time, setting the
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.Em bootverbose
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flag
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.Pq Ql Fl v
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might help in diagnosing the reason. Since the RTL 8002 requires
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the availability of a working interrupt for the printer adapter (unlike
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the
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.Xr ppc 4
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driver), the
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.Nm
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driver fails to attach if the ethernet adapter cannot assert an
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interrupt at probe time.
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.Pp
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The RTL 8002 doesn't support (hardware) multicast.
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.Pp
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The
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.Nm
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driver internally sets a flag so it gets probed very early. This way,
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it is possible to configure both, an
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.Nm
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driver as well as a
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.Xr ppc 4
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driver into the same kernel. If no RTL 8002 hardware is present, probing
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will eventually detect the printer driver.
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.Sh DIAGNOSTICS
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.Dl "rdp0: configured IRQ (7) cannot be asserted by device"
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.Pp
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The probe routine was unable to get the RTL 8002 asserting an interrupt
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request through the printer adapter.
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.Pp
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.Dl "rdp0: failed to find a valid hardware address in EEPROM"
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.Pp
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Since there doesn't seem to be a standard place for storing the hardware
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ethernet address within the EEPROM, the
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.Nm
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driver walks the entire (serial) EEPROM contents until it finds something
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that looks like a valid ethernet hardware address, based on the IEEE's
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OUI assignments. This diagnostic tells the driver was unable to find
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one. Note: it might as well be the current adapter is one of the rare
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examples with a 74S288 EEPROM, so
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.Ql flags 0x1
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should be tried.
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.Pp
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.Dl "rdp0: Device timeout"
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.Pp
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After initiating a packet transmission, the ethernet adapter didn't
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return a notification of the (successful or failed) transmission. The
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hardware is likely to be wedged, and is being reset.
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.Sh SEE ALSO
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.Xr ng_ether 4 ,
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.Xr ppc 4 ,
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.Xr ifconfig 8
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.Sh AUTHORS
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This driver was written by
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.An J\(:org Wunsch ,
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based on RealTek's packet driver for the RTL 8002, as well as on some
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description of the successor chip, RTL 8012, gracefully provided by
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RealTek.
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.Sh BUGS
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There are certainly many of them.
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.Pp
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Since the
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.Nm
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driver wants to probe its hardware at boot-time, the adapter needs
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to be present then in order to be detected.
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.Pp
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Only two out of the eight different speed modes RealTek's packet
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driver could handle are implemented. Thus there might be hardware
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where even the current slow mode is too fast.
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.Pp
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There should be a DMA transfer test in the probe routine that figures
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out the usable mode automatically.
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.Pp
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Abusing a standard printer interface for data exchange is error-prone.
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Occasional stuck hardware shouldn't surprise too much, hopefully the
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timeout routine will catch these cases. Flood-pinging is a good
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example of triggering this problem. Likewise, albeit BPF is of course
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supported, it's certainly a bad idea attempting to watch a crowded
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ethernet wire using promiscuous mode.
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.Pp
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Since the RTL 8002 has only 4 KB of Rx buffer space (2 x 2 KB are used
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as Tx buffers), the usual NFS deadlock with large packets arriving too
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quickly could happen if a machine using the
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.Nm
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driver NFS-mounts some fast server with the standard NFS blocksize of
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8 KB. (Since NFS can only retransmit entire NFS packets, the same
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packet will be retransmitted over and over again.)
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.Pp
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The heuristic to find out the ethernet hardware address from the
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EEPROM sucks, but seems to be the only sensible generic way that
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doesn't depend on the actual location in EEPROM. RealTek's sample
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driver placed it directly at address 0, other vendors picked something
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like 15, with other junk in front of it that must not be confused with
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a valid ethernet address.
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.Pp
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The driver should support the successor chip RTL 8012, which seems to
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be available and used these days. (The RTL 8002 is already somewhat
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aged, around 1992/93.) The RTL 8012 offers support for advanced
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printer adapter hardware, like bidirectional SPP, or EPP, which could
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speed up the transfers substantially. The RTL 8012 also supports
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hardware multicast, and has the ability to address 64 K x 4 packet
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buffer RAM.
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.Pp
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The driver should be layered upon the ppc driver, instead of working
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standalone, and should be available as a loadable module, so the
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device probing can be deferred until the pocket ethernet adapter has
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actually been attached.
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