Meeting Pearls 1/Meeting Pearls Vol 1 (1994).iso/installed_progs/text/faqs/linux.howto.ethernet.part1

Internet Message Format | 1994-04-26 | 60.3 KB

Subject: Linux Ethernet HOWTO (part 1/2)
Newsgroups: comp.os.linux.announce,comp.os.linux.admin,comp.answers,news.answers
From: Paul Gortmaker <[e-mail]>
Date: Mon, 25 Apr 1994 19:39:04 GMT

Archive-Name: linux/howto/ethernet/part1
Last-modified: 15 Apr 94

Linux Ethernet HOWTO v1.0 -- Last updated Mar 16, 1994
=================================================================

-- covers changes up to and including Linux kernel v1.0

INDEX:

0    Introduction.
0.01        How do I use this Guide?
0.01        Disclaimer and Copyright
0.02        Questions already?
0.03        Related Documentation
0.04        New Versions of this Document
0.05        Feedback

1    What card should I buy for Linux?
1.01        Eight bit vs 16 bit
1.02        Low price Ethernet cards
1.03        Vendors and brands to avoid.
1.04        Type of cable that your card should support

2    Status of various Ethernet cards under Linux.
2.01        3Com
2.02        Western Digital / SMC
2.03        NExxxx
2.04        Hewlett Packard Cards
2.05        D-Link
2.06        Cabletron
2.07        Allied Telesis
2.08        Arcnet
2.09        Digital / DEC
2.10        Intel
2.11        PureData
2.12        Xircom
2.13        Zenith
2.14        Racal-Interlan
2.15        AMD LANCE (79C960)
2.16        AT-Lan-Tec / RealTek Pocket adaptor
2.17        Ansel
2.18        DFI

3    Clones of popular Ethernet cards.
3.01        WD80x3 Clones
3.02        NE2000 Clones

4    Cables, coax, twisted pairs etc.
4.01        Thin Ethernet (thinnet)
4.02        Twisted Pair
4.03        Thick Ethernet

5    Technical information.
5.01        Probed addresses
5.02        Skeleton / prototype driver
5.03        Driver interface to the kernel
5.04        Interrupts and linux
5.05        Programmed I/O vs. shared mem. vs slave/master DMA
5.06        Programming the Intel chips (i82586 and i82593)
5.07        Programming information from 3Com
5.08        Notes on AMD PCnet-ISA / LANCE Based cards (79C960)
5.09        Multicast and Promiscuous mode
5.10        The Berkeley Packet Filter (BPF)
5.11        Unresolved questions / concerns

6    Possible problems, questions and troubleshooting.
6.01        Problems with NE2000 (and clones)
6.02        Problems with WD80*3 cards
6.03        Problems with 3Com cards

7    Networking with a laptop computer.
7.01        Option 1 -- using SLIP
7.02        Option 2 -- Built in NE2000 compatible or PCMCIA Ethercard.
7.03        Option 3 -- ISA Ethercard in the docking station.
7.04        Option 4 -- Pocket / parallel port adaptors.

8    Frequently asked questions.
8.01        Just the FAQ's ma'am -- just the FAQ's.

9    Miscellaneous.
9.01        Bad Vendors
9.02        Closing

======================================================================

0. Introduction.

    This is the Ethernet-HOWTO, which is a compilation of information
    about which ethernet devices can be used for Linux, and how to
    set them up.

    This Ethernet-HOWTO is by:
        Donald J. Becker    <[e-mail]>
        Paul Gortmaker        <[e-mail]>

    It covers what cards you should and shouldn't buy; how to set
    them up, how to run more than one, and other common problems and
    questions. It does *not* cover the software end of things, as that
    is covered in the NET-2 HOWTO.

    Other people who have contributed (directly or indirectly) are,
    in alphabetical order:

    Peter Bauer        <[e-mail]>
    Ross Biro        <[e-mail]>
    Alan Cox        <[e-mail]>
    David C. Davies        <[e-mail]>
    Bjorn Ekwall        <[e-mail]>
    Charles Hedrick        <[e-mail]>
    Mike Jagdis        <[e-mail]>
    Duke Kamstra        <[e-mail]>
    Russell Nelson        <[e-mail]>
    Cameron Spitzer        <[e-mail]>
    Dave Roberts        <[e-mail]>
    Glenn Talbott        <[e-mail]>
    Miquel van Smoorenburg    <[e-mail]>

    Many thanks to the above people, and all the other unmentioned
    testers out there.

0.01 How Do I Use This Guide?

    As this guide is getting bigger and bigger, you probably don't want
    to spend the rest of your afternoon reading the whole thing. And you
    don't *have* to read it all. If you haven't got an ethernet card, then
    you will want to start with section one to see what you should buy,
    and what you should avoid. If you have already got an ethernet card,
    but are not sure if you can use it with Linux, then you will want to
    read section two, which contains specific information on each
    manufacturer, and their cards. If you are having trouble with your
    card, then you will want to read the specific information about
    your card in section two and the troubleshooting information in
    section six. If you are interested in some of the technical aspects
    of the device drivers, then you can find that information in
    section 5.

0.01 Disclaimer and Copyright

    This document is *not* gospel. However, it is probably the most
    up to date info that you will be able to find. Nobody is responsible
    for what happens to your hardware but yourself. If your ethercard
    or any other hardware goes up in smoke (...nearly impossible!)
    we take no responsibility. ie. THE AUTHORS ARE NOT RESPONSIBLE
    FOR ANY DAMAGES INCURRED DUE TO ACTIONS TAKEN BASED ON THE
    INFORMATION INCLUDED IN THIS DOCUMENT.

    This document is Copyright (c) 1994 by Donald Becker and
    Paul Gortmaker. Permission is granted to make and distribute
    verbatim copies of this manual provided the copyright notice
    and this permission notice are preserved on all copies.

    Permission is granted to copy and distribute modified versions
    of this document under the conditions for verbatim copying,
    provided that this copyright notice is included exactly as in
    the original, and that the entire resulting derived work is
    distributed under the terms of a permission notice identical
    to this one.

    Permission is granted to copy and distribute translations
    of this document into another language, under the above
    conditions for modified versions.

0.02 Questions already?

    If you have questions about your ethernet card, please READ this
    document first. You may also want to join the NET channel of the
    Linux-activists mailing list by sending mail to
        [e-mail]
    with the line
        X-Mn-Admin: join NET
    at the top of the message body (not the subject). If you want to
    learn how to use the mailing channels, then send an empty message
    to the above address, and you will get an instruction manual sent
    back to you in a few hours. However, it is worth noting that the NET
    channel is primarily used for discussion of the networking code, and
    you may not see much discussion about a particular driver.
    Furthermore keep in mind that the NET channel is for development
    discussions only. General questions on how to configure your system
    should be directed to comp.os.linux.help unless you are actively
    involved in the development of part of the networking for Linux.
    We ask that you *please* respect this general guideline for content.
    You can safely bet that neither of the authors will respond to
    any plea for help that *should* be posted to c.o.l.help, but is
    inappropriately placed elsewhere.

0.03 Related Documentation

    Much of this info came from saved postings from the comp.os.linux
    groups, which shows that it is a valuable resource of information.
    Other useful information came from a bunch of small files by Donald
    himself. Some of these are found at /pub/linux/info on ftp.super.org
    [192.31.192.1] Of course, if you are setting up an Ethernet card,
    then you will want to read the NET-2 HOWTO so that you can actually
    do something with it. ftp.super.org is the home of most alpha drivers
    that are not presently in the kernel. And last but not least, the
    contributions from the individuals and companies listed above are
    greatly appreciated as well. Oh yeah, if you fancy yourself as
    a bit of a hacker, you can always scrounge some additional info
    from the driver source files as well. There is usually a paragraph
    in there describing any important points.

0.04 New versions of this document

    New versions of this document can be retrieved via anonymous
    FTP from sunsite.unc.edu:/pub/Linux/docs/HOWTO/* and various
    Linux ftp mirror sites. It will also be posted to the newsgroup
    comp.os.linux.announce at a regular interval. Updates will be made
    as new information / drivers becomes available. If this copy
    that you are reading is more than 2 months old, it is either out of
    date, or it means that I have been lazy and haven't updated it.

0.05 Feedback

    Any corrections can be sent to one of us ([e-mail]
    or [e-mail]) We will *attempt* to keep this up to date as
    more drivers become available, and as the networking code matures.

1 What card should I buy for Linux?

    For impatient users that just want a quick, cheap answer the
    summary is: get 16 bit thinnet 8013 cards. For more detail as
    to the who what where and why, read on.

1.01 Eight bit vs 16 bit

    Unless you are a light user, or are confined to using the smaller
    ISA slot, the use of the 8 bit cards like the wd8003 and the 3c503
    is really not worth the cost savings. Get the 8013 or the 3c503/16
    instead.

1.02 Low price Ethernet cards

    I keep track of the current low-price vendors, just because it's
    asked so often. Call AT-LAN-TEC at 301-948-7070. Ask for their
    technical support person, "Vincent Bono". As with all purchases,
    you should indicate you are buying this for a Linux system.
    The last I checked the price for 10 NE2000s was $480, or $48 ea.!
    NB: Their current NE2000 clone is a model that "traps" other
    drivers that probe into their address space. AT-LAN-TEC also carries
    a clone, non-EEPROM 8013 board for somewhat more, and a NE2100 clone.
    Either is a better choice if the very lowest price isn't essential.
    Also, SMC is offering an evaluation deal on their new Ultra cards,
    and the word is that you can get one for $50. You can ask them
    yourself by calling 1-800-SMC-4YOU in Canada and the USA.

    The Allied Telesis AT1500 is offered at a good price by many vendors.
    Even Inmac, known for their premium markup, has this card for under
    $100.

1.03 Vendors and Brands to Avoid

    These vendors have decided *not* to release programming information
    about their products, without signing a non-disclosure agreement.
    More information can be found in section two and 9.01. Hence it is
    strongly advised that you avoid buying products offered from
    these companies.

        (1) Cabletron
        (2) Xircom

    These particular cards should be avoided, as they are obsolete.
    The reasons as to why they have been classified as such can be
    found in section 2 of this document.

        (1) 3c501
        (2) Arcnet

1.04 Type of cable that your card should support

    Unless you have to conform to an existing network, you will want
    to use thinnet or thin ethernet cable. This is the style with the
    standard BNC connectors. See section 4 for other concerns with
    different types of ethernet cable.

    Most ethercards also come in a "Combo" version for only $10-$20 more.
    These have both twisted pair and thinnet transceiver built-in,
    allowing you to change your mind later.

2 Status of Various Ethernet Cards under Linux

    The only thing that one needs to use an ethernet card with Linux
    is the appropriate driver. For this, it is essential that the
    manufacturer will release the technical programming information to
    the general public without you (or anyone) having to sign your life
    away. A good guide for the likelihood of getting documentation
    (or, if you aren't writing code, the likelihood that someone
    else will write that driver you really, really need) is the
    availability of the Crynwr (nee Clarkson) packet driver. Russ
    Nelson (see the acknowledgements in the intro.) runs this
    operation, and has been very helpful in supporting the development
    of drivers for Linux.

    Given the documentation, you can write a driver for
    your card and use it for Linux, at least in theory. Keep in
    mind that some old hardware that was designed for XT type
    machines will not function very well in a multitasking
    environment such as Linux. Use of these will lead to major
    problems if your network sees a reasonable amount of traffic.

    Most cards come with drivers for MS-DOS interfaces such as
    NDIS and ODI, but these are useless for Linux. Many people
    have suggested directly linking them in or automatic
    translation, but this is nearly impossible. The MS-DOS
    drivers expect to be in 16 bit mode and hook into "software
    interrupts", both incompatible with the Linux kernel. This
    incompatibility is actually a feature, as some Linux drivers
    are considerably better than their MS-DOS counterparts. The
    "8390" series drivers, for instance, use ping-pong transmit
    buffers, which are only now being introduced in the MS-DOS world.

    Keep in mind that PC ethercards have the widest variety of
    interfaces (shared memory, programmed I/O, bus-master, or slave
    DMA) of any computer hardware for anything, and supporting a
    new ethercard sometimes requires re-thinking most of the lower-level
    networking code. (If you are interested in learning more about
    these different forms of interfaces, see section 5)

    Also, similar product numbers don't always indicate similar products.
    For instance, the 3c50* product line from 3Com varies wildly
    between different members.

    Enough talk. Let's get down to the information you want.

2.01 3Com

    Supported:

        3c503, 3c503/16
            3Com shared-memory ethercards. They also have a
            programmed I/O mode that doesn't use the 8390
            facilities (their engineers found too many bugs!)
            It should be about the same speed as the same bus
            width WD80x3, but I don't have a 16 bit version
            to benchmark. Unless you are a light user, spend
            the extra money and get the 16 bit model, as the
            price difference isn't significant. The 3c503 does not
            have "EEPROM setup", so the diagnostic/setup program
            isn't needed before running the card with Linux. The
            shared memory address of the 3c503 is set using jumpers
            that are shared with the boot PROM address. This is
            confusing to people familiar with other ISA cards,
            where you always leave the jumper set to "disable"
            unless you have a boot PROM.

            The Linux 3c503 driver can also work with the 3c503
            programmed-I/O mode, but this is slower and less
            reliable than shared memory mode. Also, programmed-I/O
            mode is not tested when updating the drivers, the
            deadman (deadcard?) check code may falsely timeout on
            some machines, and the probe for a 3c503 in
            programmed-I/O mode is turned off by default in some
            versions of the kernel. This was a panic reaction to
            the general device driver probe explosion; the 3c503
            shared memory probe is a safe read from memory, rather
            than an extensive scan through I/O space. As of pl13,
            the kernel has an I/O port registrar that makes I/O
            space probes safer, (see section 5.1 for more info.)
            and the programmed-I/O 3c503 probe has been re-enabled.
            You still shouldn't use the programmed-I/O mode though,
            unless you need it for MS-DOS compatibility.

            The 3c503's IRQ line is set in software, with no hints
            from an EEPROM. Unlike the MS-DOS drivers, the
            Linux driver has capability to autoIRQ: it uses the
            first available IRQ line in {5,2/9,3,4}, selected each
            time the card is 'ifconfig'ed. (Older driver versions
            selected the IRQ at boot time.) The ioctl() call
            in 'ifconfig' will return EAGAIN if no IRQ line is
            available at that time.

        3c509
            A fairly new card from 3Com. It's inexpensive and has
            excellent performance for a non-bus-master design. The
            drawbacks are that it _requires_ very low interrupt
            latency, and it isn't rated for bus speeds greater than
            8Mhz.

            A working 3c509 driver was first included as an
            alpha-test version in the 0.99pl13 kernel sources.
            It is now in the standard kernel.

            The 3c509 has a tiny Rx buffer, causing the driver to
            occasionally drop a packet if interrupts are masked for
            too long. To minimize this problem, the driver should
            be completely rewritten to use predictive interrupts.
            (Note: performance re-writes of working drivers are low
            priority unless there is some particular incentive or
            need.)

            There is also an alpha version of a Linux 3c509
            diagnostic and EEPROM setup program, but for now
            users that don't like the defaults should use the
            MS-DOS EEPROM setup program.

        3c579
            The EISA version of the 509. The current EISA version
            uses the same 16 bit wide chip rather than a 32 bit
            interface, so the performance increase isn't stunning.
            The EISA probe code was added to 3c509.c for pl14.
            We would be interested in hearing progress reports
            from any 3c579 users. (Read the above 3c509
            section for info on the driver.)

            Cameron Spitzer writes:
            "The 3C579 (Etherlink III EISA) should be configured
            as an EISA card. The IO Base Address (window 0
            register 6 bits 4:0) should be 1f, which selects EISA
            addressing mode. Logic outside the ASIC decodes the
            IO address s000, where s is the slot number. I don't
            think it was documented real well. Except for its IO
            Base Address, the '579 should behave EXACTLY like the
            '509 (EL3 ISA), and if it doesn't, I want to hear
            about it (at my work address).

            I will leave it to the Real Programmers to suggest
            the right hack to /usr/src/linux/net/inet/3c509.c to
            take care of the EISA case.

            (Note that the drivers now reside in ./drivers/net/
             and *not* ./inet/net/ --- pg.)

            Beware that if you put a '509 in EISA addressing mode
            by mistake and save that in the EEPROM, you'll have
            to use an EISA machine or the infamous Test Via to
            get it back to normal, and it will conflict at IO
            location 0 which may hang your ISA machine. It's not
            my job to say whether this is a bug or feature, but I
            have heard loud and clear that customers don't like
            it and I don't think we'll do it that way again."

    Unsupported:

        3c501
            Too brain-damaged to use. Available surplus from many
            places. Avoid it like the plague. Again, do not
            purchase this card, even as a joke. It's performance
            is horrible, and it breaks in many ways.

            (I have a standing offer: I'll pay $2 for each 3c501
            shipped to me postpaid, but only if you include the
            BNC 'T' connector and the jumpers. $2.50 if you just
            send the 'T', jumpers, and address PROM and promise to
            destroy the board. -djb)

            Cameron L. Spitzer of 3Com said:
            "I'm speaking only for myself here, of course, but I
            believe 3Com advises against installing a 3C501 in a
            new system, mostly for the same reasons Donald has
            discussed. You probably won't be happy with the
            3C501 in your Linux box. The data sheet is marked
            "(obsolete)" on 3Com's Developers' Order Form, and
            the board is not part of 3Com's program for sending
            free Technical Reference Manuals to people who need
            them. The decade-old things are nearly
            indestructible, but that's about all they've got
            going for them any more."

            For those not yet convinced, the 3c501 can only do one
            thing at a time -- while you are removing one packet
            from the single-packet buffer it cannot receive
            another packet, nor can it receive a packet while are
            loading a transmit packet. This was fine for a
            network between two 8088-based computers where
            processing each packet and replying took 10's of
            msecs, but modern networks send back-to-back
            packets for almost every transaction.

            Having read this far, you must be persistent, so you
            get let in on a secret. As of pl13, some more of
            the hardware problems were "compensated for".

            Ie. in a fit of madness I wasted a whole day updating
            my 3c501 driver and then trying to track down a few
            more of the 3c501 glitches. It now works well enough
            to NFS mount filesystems, but the receiver still
            occasionally hangs. I'm mostly certain that this is
            a hardware bug. When it hangs, the next set of
            outgoing packets will reset the board, but that's
            only useful if you have something occasionally
            generating outgoing packets.

            The driver is now in the std. kernel, but under the
            following conditions: This is unsupported code. I
            know my usual copyright says all the code is
            unsupported, but this is _really_ unsupported. I
            DON'T want to see bug reports, and I'll accept bug
            fixes only if I'm in a good mood that day.

            I don't want to see a fest of "Linux ethercards for
            sale" postings. A bunch of people have bought dozens
            of "dumpster special" 3c501s, and they hope to sell
            them at rip-off prices. A 3c501 is barely worth the
            shipping cost, and if I see people trying to sell
            them here by claiming "supported by Linux" I _will_
            flame them. They are _not_ supported by Linux.

            I don't want to be flamed later for putting out bad
            software. I don't know all all of the 3c501 bugs,
            and I know this driver only handles a few that I've
            been able to figure out. It has taken a long
            intense effort just to get the driver working this
            well.

            That said, you will find it included in "config.in"
            No special mods are needed to use it with pl15
            or greater kernels. Jumper your card to 0x280.

            AutoIRQ works, DMA isn't used, the autoprobe only
            looks at 0x280, the debug level is set with the third
            boot-time argument. You'll probably want to change
            the default EL_DEBUG to '2'.

            Once again, THE USE OF A 3c501 IS STRONGLY DISCOURAGED
            and it is NOT SUPPORTED BY LINUX.


        3c505
            An Intel-based ethercard with no driver available
            at present. (Not a very common card.)

        3c507
            This card uses one of the Intel chips, and the
            development of the driver is closely related to
            the development of the Intel Ether Express driver.
            The driver has been included in the standard
            release of pl15. You will have to un-comment
            the 3c507 line in "config.in" -- in case you
            didn't figure it out already, it is commented
            out because it is still being tested.

            Technical information is available in section 5.06,
            and if you have experience in writing drivers, see
            section 5.07 as well.

2.02 Western Digital / SMC

    The ethernet part of Western Digital has been bought by SMC. The
    SMC Elite and SMC Elite Plus are the same as late-model WD8003
    and WD8013 cards. Note that the SMC Elite Ultra is *not* the
    same as the plain SMC Elite / WD8013 card. (see below)

    Supported:

        WD8003, WD8013, SMC Elite, SMC Elite Plus
            A shared memory design by Western Digital. The
            8 bit 8003 is slightly less expensive, but only
            worth the savings for light use. Over the
            years the design has added more registers and an
            EEPROM. Clones usually go by the '8013' name, and
            usually use a non-EEPROM (jumpered) design. This part
            of WD has been sold to SMC, so you'll usually see
            something like SMC/WD8013 or SMC Elite Plus (WD8013).
            The shared memory makes the cards 10-20% faster,
            especially with larger packets. More importantly
            (to me at least) it avoids a few bugs in the
            programmed-I/O mode of the 8390, allows safe
            multi-threaded access to the packet buffer, and
            doesn't have a programmed-I/O data register that
            hangs your machine during warm-boot probes.

        SMC Elite 16 ULTRA
            This ethercard is based on a new chip from SMC, with
            a few new features. While it has a mode that is
            similar to the older SMC ethercards, it's not
            compatible with the old WD80*3 drivers. However, in
            this mode it shares most of its code with the other
            8390 drivers, while operating somewhat faster than a
            WD8013 clone.

            Some of the device probe checks in pl14 were too
            too strict, causing some cards to not be detected
            every time. This was fixed for pl14a, and hence is
            fine for pl15. Since part of the Ultra "looks" like
            an 8013, the Ultra probe is supposed to find an
            Ultra before the wd8013 probe has a chance to
            mistakenly identify it.

            Std. as of pl14, and made possible by documentation
            and ethercard loan from [e-mail],
            Duke Kamstra. If you plan on using an Ultra with Linux
            send him a note of thanks to let him know that there
            are Linux users out there!

            I'm considering writing a separate driver for the
            Ultra's "Altego" mode which allows chaining transmits
            at the cost of inefficient use of receive buffers,
            but that will probably not happen right away.
            Performance re-writes of working drivers are low
            priority unless there is some particular incentive
            or need.

2.03 NExxxx

    The prefix "NE" came from Novell Ethernet. Novell followed the
    cheapest NatSemi databook design and sold the manufacturing rights
    (spun off?) Eagle, just to get reasonably-priced ethercards into
    the market.

    Supported:

        NE1000, NE2000
            The now-generic name for a bare-bones design around
            the NatSemi 8390. They use programmed I/O rather than
            shared memory, leading to easier installation but
            slightly lower performance and a few problems. Again,
            the savings of using an 8 bit NE1000 over the NE2000
            are only warranted if you expect light use. Some
            recently introduced NE2000 clones use the National
            Semiconductor "AT/LANTic" 83905 chip, which offers
            a shared memory mode similar to the 8013 and EEPROM
            or software configuration. Some problems can arise
            with poor clones. See the question and answer section
            later in this document, and the section on clones.
            I have written a NE2000 diagnostic program, but it
            is still presently in alpha test. (ne2k)

        NE1500, NE2100
            The AT1500 driver, recently added to the list of
            supported cards, also supports the NE1500, NE2100 and
            clones. The driver shipped with pl12 kernel doesn't
            detect non-AT1500 cards with autoprobe, but will work
            fine if you specify the base address explicitly and
            jumper for DMA channel 5. Read the Allied Telesis
            section for more information on LANCE based cards.

2.04 Hewlett Packard

    The 272** cards use programmed I/O, similar to the NE*000 boards,
    but the data transfer port can be "turned off" when you aren't
    accessing it, avoiding problems with autoprobing drivers.

    Thanks to Glenn Talbott for cleaning up the confusion in this
    section regarding the version numbers of the HP hardware, and
    adding lots of new info.

    Supported:

        27245A
            8 Bit 8390 based 10BaseT, not recommended for all the
            8 bit reasons. It was re-designed a couple years
            ago to be highly integrated which caused some
            changes in initialization timing which only
            affected testing programs, not LAN drivers. (The
            new card is not 'ready' as soon after switching
            into and out of loopback mode.)

        27247B, 27252A
            The 47B is a 16 Bit 8390 based 10BaseT w/AUI, and
            the 52A is a 16 Bit 8390 based ThinLAN w/AUI.
            These cards are high performers (3c509 speed) without
            the interrupt latency problems (32K onboard RAM for TX
            or RX packet buffering). They both offer LAN
            connector autosense, data I/O in I/O space (simpler) or
            memory mapped (faster), and soft configuration. 27247B
            was rated Best for ISA Servers by PC Mag this year.

        27247A
            This is the older model that existed before the "B".
            Two versions 27247-60001 or 27247-60002 have part
            numbers marked on the card. Functionally the same to
            the LAN driver, except bits in ROM to identify
            boards differ. -60002 has a jumper to allow
            operation in non-standard ISA busses (chipsets
            that expect IOCHRDY early.)

        HP J2405A
            These are lower priced, and slightly faster than the
            27247B/27252A, but are missing some features, such
            as AUI, ThinLAN connectivity, and boot PROM socket.
            This is a fairly generic LANCE design, but a minor
            design decision makes it incompatible with a generic
            "NE2100" driver. Special support for it (including
            reading the DMA channel from the board) is in pl14
            and up, thanks to information provided by HP's Glenn
            Talbott, [e-mail]. Note that the pre pl14
            driver should not be used with this card.

            More information on LANCE based cards can be found in
            section 5.08.

2.05 D-Link

    Supported:

        DE-600
            Laptop users and other folk who might want a quick
            way to put their computer onto the ethernet may want
            to use this. The driver was included with the default
            kernel source tree as of pl12 and possibly earlier.
            Bjorn Ekwall <[e-mail]> wrote the original.
            Expect about 80kb/s transfer speed from this via the
            parallel port. You should read the README.DLINK
            file in the kernel source tree. The latest release
            of this driver is v0.32, and it is included in the
            standard kernel of pl15

        DE-650
            Some people have been using this PCMCIA card for
            some time now with their notebooks. Note however,
            that using a PCMCIA card with Linux is not trivial.
            See the section on networking with a notebook for
            more information on PCMCIA cards. This driver is
            *not* part of the standard kernel.

        DE-100, DE-200, DE-220-T
            The manual says that it is 100% compatible with the
            NE2000. This is not true. You should call them and
            tell them you are using their card with Linux, and they
            should correct their documentation. Some pre-0.99pl12
            driver versions may have trouble recognizing the DE2**
            series as 16 bit cards, and these cards are the most
            widely reported as having the spurious transfer address
            mismatch errors. Note that there are cards from
            Digital (DEC) that are also named DE100 and DE200,
            but the similarity stops there.

    Unsupported:

        DE-620
            Same as the DE-600, only with two output formats.
            (BNC and RJ-45, I would assume... ????)
            Bjorn writes: "I have still no information on the
            DE-620 that I can include in this release. (Maybe
            someone well connected to D-Link sees this,
            hint, hint, hint...)

2.06 Cabletron

    Yes, another one of these companies that won't release its
    programming information. They waited for months before actually
    confirming that all their information was proprietary, deliberately
    wasting my time. Avoid their cards like the plague if you can.
    Also note that some people have phoned Cabletron, and have been
    told things like "a [e-mail] is working on a driver
    for linux" -- making it sound like I work for them. This is
    NOT the case. Anyway, if I were working for them, or even if
    I had signed a ND agreement, I wouldn't be able to tell
    everyone what a sleazy design the E2100 is. (See below.)

    If you feel like asking them why they don't want to release their
    info so that people can use their cards, write to [e-mail]
    Tell them that you are using Linux, and are disappointed that they
    don't support open systems. (See section 9.01)

    Supported: (...well, not *really* supported)

        E10**, E10**-x, E20**, E20**-x
            These are NEx000 almost-clones that are reported to
            work with the standard NEx000 drivers, thanks to a
            ctron-specific check during the probe. If there are
            any problems, they are unlikely to be fixed, as the
            programming information is unavailable.


        E21**
            Again, there is not much one can do when the
            programming information is proprietary.
            The E2100 is a poor design. Whenever it maps its
            shared memory in during a packet transfer, it
            maps it into the *whole 128K region*! That means you
            *can't* safely use another interrupt-driven shared
            memory device in that region, including another E2100.
            It will work _most_ of the time, but every once in
            a while it will bite you. (Yes, this problem can
            be avoided by turning off interrupts while
            transferring packets, but that will almost certainly
            lose clock ticks.

            Also, don't confuse the E2100 for a NE2100 clone.
            The E2100 is a shared memory NatSemi DP8390 design,
            roughly similar to a brain-damaged WD8013, whereas
            the NE2100 (and NE1500) use a bus-mastering AMD
            LANCE design.

            There is an alpha test driver available (even though
            I shouldn't have bothered) in the normal place
            (see the FAQ section) -- e2100.c -- let me know if
            you use it, and how it works. Don't forget to
            un-comment the line in config.in.

2.07    Allied Telesis

    Allied Telesis is the worlds largest maker of separate
    transceivers thanks to their low prices, and they now have a
    series of low-cost ethercards using the 79C960 version of the AMD
    LANCE. These are bus-master cards, and thus probably the fastest
    ISA bus ethercards available (although the 3c509 has lower latency
    thanks to predictive interrupts).

    Supported:

        AT1500
            The driver for the AT1500 series is new in the
            0.99pl12 kernel, but it won't work "out-of-the-box"
            with >16M machines. (NB This isn't a fundamental
            limitation, so stop pointing and laughing at the ISA
            bus. The driver just needs a hook to allocate
            low-memory buffers for the bus-master DMA, and should
            be just as fast on >16M systems. It can be easily
            fixed by initializing the LANCE driver with the
            character devices, but this fix depends on the
            resolution of the networking code uncertainty.)

            For the ISA bus master mode all structures used
            directly by the LANCE, the initialization block,
            Rx and Tx rings, and data buffers, must be accessible
            from the ISA bus, i.e. in the lower 16M of real memory.
            This is a problem for current Linux kernels on >16M
            machines. The network devices are initialized after
            memory initialization, and the kernel doles out memory
            from the top of memory downward. The current solution
            is to have a special network initialization routine
            that's called before memory initialization; this will
            eventually be generalized for all network devices.
            Low-memory "bounce-buffers" are used when needed.

            This driver should also work with NE1500 and NE2100
            clones.

            Future driver versions may figure out a way to
            autoDMA. Although there is no autoDMA (until I verify
            that autoDMA is safe and reliable), some versions
            (pl13) allow passing the DMA channel at boot-time via
            LILO. (Boot-time parameters can be made permanent in
            LILO v13+, read the docs.) The DMA channel otherwise
            defaults to DMA5.

            In pl14, there was a buglet that would hang some
            machines with AT1500 like cards. Either get pl15
            or newer, or go into ./init/main.c and move the
            sti(); and claibrate_delay(); (near line 366) in
            *front of* the #ifdef CONFIG_INET, instead of
            after it.

            Please report the exact chip used by your ethercard,
            and any success or failure you have. This driver is
            still young, and I've gotten few reports.

            More information on AMD LANCE based Ethernet cards
            can be found in section 5.08.

        AT1700
            The Allied Telesis AT1700 series ethercards are based
            on the Fujitsu MB86965. This chip uses a programmed
            I/O interface, and a pair of fixed-size transmit
            buffers. This allows small groups of packets to sent
            be sent back-to-back, with a short pause while
            switching buffers.

            A unique feature is the ability to drive 150ohm STP
            (Shielded Twisted Pair) cable commonly installed for
            Token Ring, in addition to 10baseT 100ohm UTP
            (unshielded twisted pair).

            A mis-feature to watch out for is that the current
            production version silently wires to DMA channel 5,
            rendering it useless. No device driver will be
            written using DMA if installing a second card into
            the machine breaks both, and the only way to disable
            the DMA is with a knife.

            The at1700 driver is included in the standard pl15
            kernel source tree.

2.08 Arcnet

    There is no Arcnet driver for Linux. Feel free to write a driver. With
    the very low cost and better performance of ethernet, I expect that
    most places will be giving away their Arcnet hardware for free,
    resulting in a lot of home systems with Arcnet.

    An advantage of Arcnet is that all of the cards have identical
    interfaces, so once a driver is available it will work for everyone.

2.09 Digital / DEC

    Supported: DE200, DE210, DE202, DE100, DEPCA rev E

        As of linux v1.0, there is a driver included as standard
        for these cards. It was written by David C. Davies.
        There is documentation included in the source file
        "depca.c", which includes info on how to use more than
        one of these cards in a machine.

        If you have / want to use the pl15 kernel or older,
        then you will have to use Peter Bauer's driver.
        It can be found as a separate patch called depca-0.8.tar.gz.
        You will have to un-comment the DEPCA line in "config.in"
        after installing the patch. You can find the patch on
        ftp.funet.fi, /pub/OS/Linux/BETA/depca/depca-0.8.tar.gz
        This version resets the card upon close so that you can
        use it with broken DOS drivers after a warm boot.


    Unsupported: Digital Etherlink III

        Peter Bauer said that "the new etherlink III seems to
        be a break: No official docu from DEC as far as today,
        other (incompatible??) hardware used, and (no joke) (at least
        for the first delivered cards) also a sharp knife necessary
        to get the card working (needs cut of some irq lines ...)
        As far as I know, lots of DEC Employees use Linux (at least
        for hobby purposes) and the depca-driver, because its a
        de-facto standard in DEC, so I encourage any DEC-employee
        reading this to check wether my writing is true, and to
        support sources of information about the etherworks-III."

2.10 Intel Ethernet Cards

    Supported: Ether Express

        This card uses the intel i82586. (Surprise, huh?)
        The driver is in the standard release of pl15.
        However, you will have to uncomment the line in
        "config.in" to use it. -- yes, this line is
        commented out for a reason. The driver is still
        in the testing phases, as of v1.0 as well.

        There is some technical information available on
        the i82586 in section 5.06, and also in the
        source code for the driver "eexpress.c". Don't
        be afraid to read it. ;-)

        The rason is that the driver works well with slow machines,
        but the i82586 occasionally hangs from the packet buffer
        contention that a fast machine can cause. I'll have
        to find a work-around before releasing the driver.
        One reported hack fix is to change all of the outw()
        calls to outw_p().


        If you do try the driver please post or send a report.
        Include the kind of machine you are trying it with,
        and how heavily loaded your network is.


2.11 PureData

    Supported: PDUC8028, PDI8023

        The PureData PDUC8028 and PDI8023 series of cards are reported
        to work, thanks to special probe code contributed by Mike
        Jagdis <[e-mail]>. The support is integrated
        with the WD driver.

2.12 Xircom

    Another group that won't release documentation. No cards
    supported. Don't look for any support in the future unless
    they release their programming information. And this is
    highly unlikely, as they *forbid* you from even reverse-
    engineering their drivers. If you are already stuck with one,
    see if you can trade it off on some DOS (l)user. Read section
    9.01 if you are bored.

    And if you just want to verify that this is the case, you can
    reach Xircom at 1-800-874-7875 or [phone].

2.13 Zenith

    The built-in Z-Note network adaptor is based on the Intel
    i82593 using two DMA channels. There might be a driver for it
    in mid 1994. See section 5.06 for more information.
    Also note that the Z-Note is compatible with the IBM ThinkPad 300.

2.14 Racal-Interlan

    Note: I have been told that the following two drivers are
    for patchlevel 11, and hence are a bit dated. The original
    author is Michael Hipp, and can be reached at the following addr:
        [e-mail]

    NI52**

    There is an alpha driver for the NI5210 floating about.
    (last seen on tsx-11.mit.edu /pub/linux/ALPHA/ni/ni52.tar.gz)
    This card also uses one of the Intel chips. See section
    5.06 for more information.

    NI65**

    There is also a driver for the LANCE based NI6510, and it
    can be found in the same place as the NI5210 driver above.
    I am not sure how much work it would be to hack the current
    LANCE driver in the kernel to support this card. If anyone
    has done so, let me know.

2.15 AMD LANCE (79C960)

    There really is no AMD ethernet card. You are probably reading this
    because the only markings you could find on your card said AMD
    and the above number. The above number refers to a chip from AMD
    that is the heart of many ethernet cards. See the section on the
    Allied Telesis AT1500, the NE1500/2100 and the information in
    section 5.08. Chances are that the existing LANCE driver will work
    with all AMD LANCE based cards. (...except perhaps the above
    mentioned NI6510 ???)

2.16 AT-Lan-Tec / RealTek Pocket adaptor

    This is a generic, low-cost OEM pocket adaptor being sold by
    AT-Lan-Tec, and (likely) a number of other suppliers. A
    driver for it is included in the standard pl15 kernel.
    Note that there is substantial information contained in the
    driver source file "atp.c" which presently lives in ./drivers/net/
    BTW, the adaptor (AEP-100L) has both 10baseT and BNC connections!
    You can reach AT-Lan-Tec at 1-301-948-7070. Ask for the model
    that works with Linux, or ask for "Vincent Bono" in tech support.
    In the Netherlands a compatible adaptor is sold under the name SHI-TEC
    PE-NET/CT, and sells for about $125. The vendor was Megasellers.
    They state that they do not sell to private persons, but I just
    gave them the name of my home institute. No questions asked.
    They are: Megasellers, Vianen, The Netherlands. They always
    advertise in Dutch computer magazines. In Germany, a similar
    adaptor comes as a no-brand-name product. Prolan 890b, no
    brand on the casing, only a roman II. Resellers can get a price
    of about $130, including a small wall transformer for the power.

    Physical Description

    The adaptor is "normal size" for the product class, about 57mm wide,
    22mm high tapering to 15mm high at the DB25 connector, and 105mm long
    (120mm including the BNC socket). It's switchable between the RJ45
    and BNC jacks with a small slide switch positioned between the two:
    a very intuitive design.

    It's powered by a lightweight 5V "wall brick" adaptor that terminates
    in a standard 5.0mm power connector. I measured an unconnected
    quiescent power draw of 102ma for BNC and 84ma for 10baseT. I hooked
    the pocket adaptor up to my home thinnet and started FTPing a large
    file. The power measurements were:

        idle, connected        99ma @ 5.1V
        active, connected    107ma @ 5.1V

    This was measured using a Fluke 8026B true-RMS multimeter, so I'm
    pretty confident the numbers are good. This power draw is low enough
    that you could buy or build a cable to take the 5V directly from the
    keyboard/mouse port available on many laptops. (Bonus points here
    for using a standardized power connector instead of proprietary one.)

2.17 Ansel

    Supported: AC3200 EISA

        This driver is not included in the pl15 kernel. To
        *alpha* test it, get the files ac3200.[c,h] from
        where you usually get alpha drivers (see the FAQ in
        this document if you dont know) and uncomment the
        line in config.in for the ac3200. If you use it,
        please let me know how things work out.

2.18 DFI

    Supported: DFINET-300 (NE1000) and DFINET-400 (NE2000)

        These cards are now detected (as of pl15) thanks to
        Eberhard Moenkeberg <[e-mail]> who noted that
        they use "DFI" in the first 3 bytes of the prom, instead
        of using 0x57 in bytes 14 and 15, which is what all the
        NE1000 and NE2000 cards use.

3. Clones of popular Ethernet cards.

    Due to the popular design of some cards, different companies will
    make "clones" or replicas of the original card. However, one must
    be careful, as some of these clones are not 100% compatible, and
    can be troublesome. Some common problems with "not-quite-clones"
    are noted in the question and answer section of this document.

    Also note that if your card isn't mentioned here, that really
    means nothing. Chances are that even if it is only a half decent
    clone of the original, then it will still work.

3.1 WD80x3 clones

    The following clones are reported to work with the standard
    WD80x3 driver:

    AT-LAN-TEC 8013
    PureData (not a 8013 clone, but the 8013 driver has special code)
    LANNET LEC-45
    PE-8013 (WD-8013 Compatible)

3.2 NE2000 clones

    The following clones are reported to work with the standard
    NE2000 driver:

    Accton NE2000 (might not get detected at boot, see section 6)
    Alta Combo NE2000 clone
    Aritsoft LANtastic AE-2 (OK, but has flawed error-reporting registers)
    Asante Etherpak 2001/2003
    AT-LAN-TEC NE2000 clone (uses Winbond chip that traps SCSI drivers)
    Cabletron products: E10**, E10**-x, E20**, E20**-x
    Cnet UTP 10baseT (NE 2000 emulation)
    D-Link Ethernet II (bad clones, but the driver checks for them)
    4-Dimension FD0490 EtherBoard16
    LTC E-NET/16 P/N: 8300-200-002 ([e-mail])
    Network Solutions HE-203
    SIIG Inc E-Lan/200 (NE 2000 comp.)
    SVEC 4 Dimension Ethernet

4. Cables, coax, twisted pairs etc.

    If you are starting a network from scratch, it's considerably less
    expensive to use thin ethernet, RG58 co-ax cable with BNC connectors,
    than old-fashioned thick ethernet, RG-5 cable with N connectors, or
    10baseT, twisted pair telco-style cables with RJ-45 eight wire "phone"
    connectors.

4.01 Thin Ethernet (thinnet)

    Thin ethernet is the "ether of choice". The cable is inexpensive. If
    you are making your own cables solid-core RG58A is $0.09/ft. and
    stranded RG58AU is $0.15/ft. Twist-on BNC connectors are < $2 ea.,
    and other misc. pieces are similarly inexpensive. It is essential
    that you properly terminate each end of the cable with 50 ohm
    terminators, so budget $2 ea. for a pair. It's also vital that
    your cable have no "stubs" -- the 'T' connectors must be attached
    directly to the ethercards. The only drawback is that if you have
    a big loop of machines connected together, and some bonehead breaks
    the loop by taking one cable off the side of his tee, the whole
    network goes down because it sees an infinite impedance (open
    circuit) instead of the required 50 ohm termination. Note that
    you can remove the tee piece from the card itself without killing
    the whole subnet, as long as you don't remove the cables from the
    tee itself. Of course this will disturb the machine that you
    pull the actual tee off of. 8-) And if you are doing a small
    network of two machines, you *still* need the tees and the 50 ohm
    terminators -- you *can't* just cable them together!


4.02 Twisted pair

    Twisted pair networks require active hubs, which start around $200,
    and the raw cable cost can actually be higher than thinnet. They are
    usually sold using the claim that you can use your existing telephone
    wiring, but it's a rare installation where that turns out to be the
    case. The claim that you can upgrade to higher speeds is also
    suspect, as most proposed schemes use higher-grade (read $$) cable and
    more sophisticated termination ($$$) than you would likely install on
    speculation. New gizmos are floating around which allow you to
    daisy-chain machines together, and the like. For example,
    Falleron sells EtherWave adaptors and transceivers. This device
    allows multiple 10baseT devices to be daisy-chained. They also
    sell a 3c509 clone that includes the EtherWave transceiver.
    The drawback is that it's more expensive and less reliable than a
    cheap ($100-$150) mini-hub and another ethercard. IMO, you should
    either go for the hub approach or switch over to 10base2 thinnet.

    On the other hand, hubs are rapidly dropping in price, all 100Mb/sec
    ethernet proposals use twisted pair, and most new business
    installations use twisted pair. (This is probably to avoid the
    problem with idiots messing with the BNC's as described above.)

    If you are only connecting two machines, it is possible to avoid
    using a hub, by swapping the Rx and Tx pairs (1-2 and 3-6).

    Also, Russ Nelson adds that "New installations should use Category 5
    wiring. Anything else is a waste of your installer's time, as
    100Base-whatever is going to require Cat 5."

4.03 Thick Ethernet

    Thick ethernet is mostly obsolete, and is usually used only to remain
    compatible with an existing implementation. You can stretch the rules
    and connect short spans of thick and thin ethernet together with a
    passive $3 N-to-BNC connector, and that's often the best solution to
    expanding an existing thicknet. A correct (but expensive) solution is
    to use a repeater in this case.


5 Technical information.

    For those who want to play with the present drivers, or try to make
    up their own driver for a card that is presently unsupported, this
    information should be useful. If you do not fall into this category,
    then perhaps you will want to skip this section.

5.01 Probed addresses

    While trying to determine what ethernet card is there, the following
    addresses are autoprobed, assuming the type and specs of the card
    have not been set in the kernel. As of 0.99pl12, doing a "make config"
    will ask what cards are to be supported. The file names below are
    in /usr/src/linux/drivers/net/
    ----------------------------------------------------------------
    wd.c:        0x300, 0x280, 0x380, 0x240
    3c501.c        0x280
    3c503.c:    0x300, 0x310, 0x330, 0x350, 0x250, 0x280, 0x2a0, 0x2e0
    3c507.c:    0x300, 0x320, 0x340, 0x280
    3c509.c:    <Special "ID Port" probe>
    at1700.c:    0x300, 0x280, 0x380, 0x320, 0x340, 0x260, 0x2a0, 0x240
    atp.c:        0x378, 0x278, 0x3bc
    depca.c        0x300, 0x200
    d_link.c:    0x378
    ne.c:        0x300, 0x280, 0x320, 0x340, 0x360
    hp.c:        0x300, 0x320, 0x340, 0x280, 0x2C0, 0x200, 0x240
    lance.c:    0x300, 0x320, 0x340, 0x360
    smc-ultra.c:    0x200, 0x220, 0x240, 0x280, 0x300, 0x340, 0x380
    eexpress.c:    0x300, 0x270, 0x320, 0x340
    3c509.c:    <Special "ID Port" probe>
    ----------------------------------------------------------------
    There are some NE2000 clone ethercards out there that are waiting black
    holes for autoprobe drivers. While many NE2000 clones are
    safe until they are enabled, some can't be reset to a safe mode.
    These dangerous ethercards will hang any I/O access to their
    "dataports". The typical dangerous locations are:

    Ethercard jumpered base     Dangerous locations (base + 0x10 - 0x1f)
        0x300 *                0x310-0x317
        0x320                0x330-0x337
        0x340                0x350-0x357
        0x360                0x370-0x377

    * The 0x300 location is the traditional place to put an ethercard, but
    it's also a popular place to put other devices (often SCSI
    controllers). The 0x320 location is often the next one chosen, but
    that's bad for for the AHA1542 driver probe. The 0x360 location is
    bad, because it conflicts with the parallel port at 0x378.

    To avoid these lurking ethercard, here are the things you can do:

    o Probe for the device's BIOS in memory space. This is easy
      and always safe, but it only works for cards that always have
      BIOSes, like primary SCSI controllers.

    o Avoid probing any of the above locations until you think
      you've located your device. The NE2000 clones have a reset range
      from <base>+0x18 to <base>+0x1f that will read as 0xff, so probe
      there first if possible. It's also safe to probe in the 8390
      space at <base>+0x00 - <base>+0x0f, but that area will return
      quasi-random values

    o If you must probe in the dangerous range, for instance if your
      target device has only a few port locations, first check that
      there isn't an NE2000 there. You can see how to do this by
      looking at the probe code in /usr/src/linux/net/inet/ne.c

    In other news, I've written the code for the I/O port registrar.
    Peter MacDonald and I have been intensely discussing this, and I think
    our current scheme has the necessary functionality with minimal kernel
    size impact. (The implementation involved rewriting the bitmap ops in
    kernel/ioport.c:ioperm() so that most code could be shared.)

    Here is the current "blurb". As usual comments are welcome. Please
    keep them substantial and constructive (we've already talked about
    changing the name from "reserve=" to "noprobe=").

    ==================

    Boot-Time Parameters: "reserve="

    In some machines it may be necessary to prevent device drivers from
    checking for devices (auto-probing) in a specific region. This may be
    because of poorly designed hardware that causes the boot to "freeze"
    (such as some ethercards), hardware that is mistakenly identified,
    hardware whose state is changed by an earlier probe, or merely
    hardware you don't want the kernel to initialize.

    The "reserve" boot-time argument addresses this problem by specifying
    an I/O port region that shouldn't be probed. That region is reserved
    in the kernel's port registration table as if a device has already
    been found in that region. Note that this mechanism shouldn't be
    necessary on most machine, only when there is a problem or special
    case.

    The boot-line syntax is

      lilo-prompt: linux-image reserve=[<port>,<size>,<port>,<size>...]

    As usual with boot-time specifiers there is an 11 parameter limit, thus
    you can only specify 5 reserved regions per "reserve" keyword.
    Multiple "reserve" specifiers will work if you have an usually
    complicated request.

    If you specify a "reserve" region to protect a specific device, you
    must generally specify an explicit probe for that device. Most
    drivers ignore the port registration table if they are given an
    explicit address.

5.02 Skeleton / prototype driver

    OK. So you have decided that you want to write a driver for the
    Foobar Ethernet card, as you have the programming information,
    and it hasn't been done yet. (...these are the two main require-
    ments ;-) You can use the skeleton network driver that is provided
    with the Linux kernel source tree. It can be found in the file
    /usr/src/linux/drivers/net/skeleton.c as of 0.99pl15, and later.

    It's also very useful to look at the Crynwr (nee Clarkson) driver
    for your target ethercard, if it's available. Russ Nelson
    <[e-mail]> has been actively updating and writing these,
    and he has been very helpful with his code reviews of the current
    Linux drivers.

5.03 Driver interface to the kernel

    Here are some notes that may help when trying to figure out what
    the code in the driver segments is doing, or perhaps what it is
    supposed to be doing.

    =====================================================

    int ethif_init(struct device *dev)
    {
        ...
        dev->send_packet = &ei_send_packet;
        dev->open = &ei_open;
        dev->stop = &ei_close;
        dev->hard_start_xmit = &ei_start_xmit;
        ...
    }

    int ethif_init(struct device *dev)

    This function is put into the device structure in Space.c. It is
    called only at boot time, and returns '0' iff the ethercard 'dev'
    exists.

    =====================================================

    static int ei_open(struct device *dev)
    static int ei_close(struct device *dev)

    This routine opens and initializes the board in response to an
    socket ioctl() usually called by 'config' or 'ifconfig'. It is
    commonly stuffed into the 'struct device' by ethif_init().

    The inverse routine is ei_close(), which should shut down the
    ethercard, free the IRQs and DMA channels if the hardware permits,
    and turn off anything that will save power (like the transceiver).

    (Note: As of NET-2, the relevant program is '/etc/ifconfig' - and
    the device *can* be turned off or on via passing 'up' or 'down'
    to 'ifconfig' from the command line with the device name.)

    =====================================================

    static int ei_start_xmit(struct sk_buff *skb, struct device *dev)
        dev->hard_start_xmit = &ei_start_xmit;

    This routine puts packets to be transmitted into the hardware. It
    is usually stuffed into the 'struct device' by ethif_init().

    When the hardware can't accept additional packets it should set
    the dev->tbusy flag. When additional room is available, usually
    during a transmit-complete interrupt, dev->tbusy should be cleared
    and the higher levels informed with mark_bh(INET_BH).
    [[Note: pre0.99.4 kernels didn't use this interface for all packets.]]

    =====================================================

    ...
        if (dev_rint(buffer, length, is_skb ? IN_SKBUFF : 0, dev))
           stats->rx_dropped++;
    ...
    A received packet is passed to the higher levels using dev_rint().
    If the unadorned packet data in a memory buffer, dev_rint will copy
    it into a 'skbuff' for you. Otherwise a new skbuff should be
    kmalloc()ed, filled, and passed to dev_rint() with the IN_SKBUFF flag.

    =====================================================

5.04 Interrupts and Linux

    There are two kinds of interrupt handlers in Linux:
    fast ones and slow ones. You decide what kind you are installing by
    the flags you pass to irqaction(). The fast ones, such as the serial
    interrupt handler, run with _all_ interrupts disabled. The normal
    interrupt handlers, such as the one for ethercard drivers, runs with
    other interrupts enabled.

    There is a two-level interrupt structure. The "fast" part handles the
    device register, removes the packets, and perhaps sets a flag.  After
    it is done, and interrupts are re-enabled, the slow part is run if the
    flag is set.

    The flag between the two parts is set by:
        mark_bh(INET_BH);

    Usually this flag is set within dev_rint() during a received-packet
    interrupt, and set directly by the device driver during a
    transmit-complete interrupt.

    You might wonder why all interrupt handlers cannot run in
    "normal mode" with other interrupts enabled. Ross Biro uses this
    scenario to illustrate the problem:
        o You get a serial interrupt, and start processing it.
          The serial interrupt is now masked.
        o You get a network interrupt, and you start transferring
          a maximum-sized 1500 byte packet from the card.
        o Another character comes in, but this time the interrupts
          are masked!

    The "fast" interrupt structure solves this problem by allowing
    bounded-time interrupt handlers to run without the risk of leaving
    their interrupt lines masked by another interrupt request.

    There is an additional distinction between fast and slow interrupt
    handlers -- the arguments passed to the handler. A "slow" handler is
    defined as

        static void
        handle_interrupt(int reg_ptr)
        {
            int irq = -(((struct pt_regs *)reg_ptr)->orig_eax+2);
            struct device *dev = irq2dev_map[irq];
        ...

    While a fast handler gets the interrupt number directly

        static void
        handle_fast_interrupt(int irq)
        {
        ...

    A final aspect of network performance is latency. The only board
    that really addresses this is the 3c509, which allows a predictive
    interrupt to be posted. It provides an interrupt response timer so
    that the driver can fine-tune how early an interrupt is generated.

    Alan Cox has some advice for anyone wanting to write drivers
    that are to be used with pl14 kernels and newer. He says:

    "Any driver intended for pl14 should use the new alloc_skb() and
    kfree_skbmem() functions rather than using kmalloc() to obtain an
    sk_buff. The new pl14 skeleton does this correctly. For drivers
    wishing to remain compatible with both sets the define
    'HAVE_ALLOC_SKB' indicates these functions must be used.

    In essence replace

        skb=(struct sk_buff *)kmalloc(size)
    with

        skb=alloc_skb(size)

    and

        kfree_s(skb,size)

    with

        kfree_skbmem(skb,size)    /* Only sk_buff memory though */

    Any questions should I guess be directed to me since I made the change.
    This is a change to allow tracking of sk_buff's and sanity checks on
    buffers and stack behaviour. If a driver produces the message
    'File: ??? Line: ??? passed a non skb!' then it is probable the
    driver is not using the new sk_buff allocators."


5.05 Programmed I/O vs. shared mem. vs. slave/master DMA

    Ethernet is 10Mbs. (Don't be pedantic, 3Mbs and 100Mbs don't count.)
    If you can already send and receive back-to-back packets, you just
    can't put more bits over the wire. Every modern ethercard can receive
    back-to-back packets. The Linux DP8390 drivers come pretty close to
    sending back-to-back packets (depending on the current interrupt
    latency) and the 3c509 and AT1500 hardware has no problem at all
    automatically sending back-to-back packets.

    The ISA bus can do 5.3MB/sec (42Mb/sec), which sounds like more than
    enough. You can use that bandwidth in several ways:

    Programmed I/O
    ==============
      Pro: Doesn't use any constrained system resources,
           just a few I/O registers, and has no 16M limit.
      Con: Usually the slowest transfer rate, the CPU is waiting
           the whole time, and interleaved packet access is usually
           difficult to impossible.

    Shared memory
    =============
      Pro: Simple, faster than programmed I/O, and allows random
           access to packets.
      Con: Uses up memory space (a big one for DOS users, only a minor
           issue under Linux), and it still ties up the CPU.

    Slave (normal) DMA
    ==================
      Pro: Frees up the CPU during the actual data transfer.
      Con: Checking boundary conditions, allocating contiguous buffers,
           and programming the DMA registers makes it the slowest
           of all techniques.  It also uses up a scarce DMA
           channel, and requires aligned low memory buffers.

    Master (bus-master) DMA
    =======================
      Pro: Frees up the CPU during the data transfer, can string together
           buffers, can require little or no CPU time lost on the
           ISA bus.
      Con: Requires low-memory buffers and a DMA channel. Any
           bus-master will have problems with other bus-masters that
           are bus-hogs, such as some primitive SCSI adaptors. A few
           badly-designed motherboard chipsets have problems with
           bus-masters. And a reason for not using *any* type of
           DMA device is using a Cyrix 486 processor designed for
           plug-in replacement of a 386: these processors must
           flush their cache with each DMA cycle.

---End of part 1/2---