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RDP(4) FreeBSD/i386 Kernel Interfaces Manual RDP(4) NAME rdp -- Ethernet driver for RealTek RTL 8002 pocket ethernet SYNOPSIS device rdp0 at isa? port 0x378 irq 7 device rdp0 at isa? port 0x378 irq 7 flags 0x2 DESCRIPTION The rdp device driver supports RealTek RTL 8002-based pocket ethernet adapters, connected to a standard parallel port. These adapters seem to belong to the cheaper choices among pocket ether- net adapters. The RTL 8002 is the central part, containing an interface to BNC and UTP (10 Mbit/s) media, as well as a host interface that is designed to talk to standard parallel printer adapters. For the full ethernet adapter to work, it is completed by an external RAM used as the Tx and Rx packet buffer (16 K x 4 for the RTL 8002), and an EEPROM to hold the assigned ethernet hardware address. For the RTL 8002, the EEP- ROM can be either a standard 93C46 serial EEPROM (which seems to be a common choice), or a 74S288 parallel one. The latter variant needs the device configuration flag 0x1 in order to work. Since standard printer adapters seem to vary wildly among their timing requirements, there are currently two possible choices for the way data are being exchanged between the pocket ethernet adapter and the printer interface. The default is the fastest mode the RTL 8002 supports. If the printer adapter to use is particularly slow (which can be noticed by watching the ethernet wire for crippled packets, or by not seeing cor- reclty received packets), the configuration flag 0x2 can be set in order to throttle down the rdp driver. Note that in fast mode, the data rate is assymetric, sending is a little faster (up to two times) than receiv- ing. Rates like 150 KB/s for sending and 80 KB/s for receiving are com- mon. For slow mode, both rates are about the same, and in the range of 50 KB/s through 70 KB/s. As always, your mileage may vary. In case the adapter isn't recognized at boot-time, setting the bootverbose flag (`-v') might help in diagnosing the reason. Since the RTL 8002 requires the availability of a working interrupt for the printer adapter (unlike the ppc(4) driver), the rdp driver fails to attach if the ethernet adapter cannot assert an interrupt at probe time. The RTL 8002 doesn't support (hardware) multicast. The rdp driver internally sets a flag so it gets probed very early. This way, it is possible to configure both, an rdp driver as well as a ppc(4) driver into the same kernel. If no RTL 8002 hardware is present, probing will eventually detect the printer driver. DIAGNOSTICS rdp0: configured IRQ (7) cannot be asserted by device The probe routine was unable to get the RTL 8002 asserting an interrupt request through the printer adapter. rdp0: failed to find a valid hardware address in EEPROM Since there doesn't seem to be a standard place for storing the hardware ethernet address within the EEPROM, the rdp driver walks the entire (serial) EEPROM contents until it finds something that looks like a valid ethernet hardware address, based on the IEEE's OUI assignments. This diagnostic tells the driver was unable to find one. Note: it might as well be the current adapter is one of the rare examples with a 74S288 EEPROM, so `flags 0x1' should be tried. rdp0: Device timeout After initiating a packet transmission, the ethernet adapter didn't return a notification of the (successful or failed) transmission. The hardware is likely to be wedged, and is being reset. SEE ALSO ng_ether(4), ppc(4), ifconfig(8) AUTHORS This driver was written by Jorg Wunsch, based on RealTek's packet driver for the RTL 8002, as well as on some description of the successor chip, RTL 8012, gracefully provided by RealTek. BUGS There are certainly many of them. Since the rdp driver wants to probe its hardware at boot-time, the adapter needs to be present then in order to be detected. Only two out of the eight different speed modes RealTek's packet driver could handle are implemented. Thus there might be hardware where even the current slow mode is too fast. There should be a DMA transfer test in the probe routine that figures out the usable mode automatically. Abusing a standard printer interface for data exchange is error-prone. Occasional stuck hardware shouldn't surprise too much, hopefully the timeout routine will catch these cases. Flood-pinging is a good example of triggering this problem. Likewise, albeit BPF is of course supported, it's certainly a bad idea attempting to watch a crowded ethernet wire using promiscuous mode. Since the RTL 8002 has only 4 KB of Rx buffer space (2 x 2 KB are used as Tx buffers), the usual NFS deadlock with large packets arriving too quickly could happen if a machine using the rdp driver NFS-mounts some fast server with the standard NFS blocksize of 8 KB. (Since NFS can only retransmit entire NFS packets, the same packet will be retransmitted over and over again.) The heuristic to find out the ethernet hardware address from the EEPROM sucks, but seems to be the only sensible generic way that doesn't depend on the actual location in EEPROM. RealTek's sample driver placed it directly at address 0, other vendors picked something like 15, with other junk in front of it that must not be confused with a valid ethernet address. The driver should support the successor chip RTL 8012, which seems to be available and used these days. (The RTL 8002 is already somewhat aged, around 1992/93.) The RTL 8012 offers support for advanced printer adapter hardware, like bidirectional SPP, or EPP, which could speed up the transfers substantially. The RTL 8012 also supports hardware multi- cast, and has the ability to address 64 K x 4 packet buffer RAM. The driver should be layered upon the ppc driver, instead of working standalone, and should be available as a loadable module, so the device probing can be deferred until the pocket ethernet adapter has actually been attached. FreeBSD 11.1 December 21, 1998 FreeBSD 11.1
NAME | SYNOPSIS | DESCRIPTION | DIAGNOSTICS | SEE ALSO | AUTHORS | BUGS
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