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    SubjectRe[2]: 2.6.16 serious consequences / GPL_EXPORT_SYMBOL / USB drivers of major vendor excluded
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    Date
    We are pleased to note that the GPL_EXPORT_SYMBOL fix has been withdrawn.
    This is particularly important for customers who have been relying on good
    driver coverage for ISDN/DSL devices with SUSE distributions over the past
    few years. However, as we understand the ongoing discussion, a number of
    people are tending towards a position of enforcement of USB GPL drivers
    only. We would like to take this opportunity to clarify where we see the
    differences between AVM and other devices and the difficulties regarding a
    possible move towards user mode.

    The user space does not ensure the reliability of time critical analog
    services like Fax G3 or analog modem emulations. This quality of service
    can only be guaranteed within the kernel space.

    Let me explain that issue using the FaxG3-service as an example. Fax G3
    (T.30) is not specified as a data protocol with error-free transmission.
    Let us assume, there is a system peak demand on the host system, while a
    fax is incoming, e.g. because of a parallel access of a higher prioritized
    process. Handled in user mode, the user gets broken or fragmented faxes as
    a result. Same for the communication with analogue remote stations (modems)
    over a digital net (ISDN). You cannot speak about reliable quality of
    service anymore. Only the kernel offers low latency and timeline processing
    which is required for soft DSP alike processing. This should be OS
    independent and from our point of view, Linux should not be inferior to any
    other OS.

    Of course, other OS also have the concept of shifting usb drivers to user
    space, but time critical demands are explicitly excluded. The given
    examples gPhoto und rio500 at
    http://libusb.sourceforge.net/doc/examples-other.html operate mostly
    unidirectionally. Isochronical services within the libusb, especially the
    USB driver framework for the user mode are not ready for bidirectional
    operation. Even though the current libusb development started integrating
    the isochronous transfer support, it still is under construction and it is
    unclear if this task can be accomplished at all (see statement from
    Johannes Erdfelt at
    http://sourceforge.net/mailarchive/forum.php?thread_id=9531397&forum_id=5425
    ).

    In contrast, AVM's driver concept is established for many years now. So the
    user mode does not seem to be an alternative for ISDN/DSL communication
    devices at the moment. Moreover, a rework of more than 30 devices would
    consume a lot of development resources. You will hardly find a similiar
    company situation. We are not talking about a 10 to 20kByte mouse driver,
    but rather >600kByte of complex work per device. Take a look at the
    FRITZ!Card PCI package
    atftp://ftp.avm.de/cardware/fritzcrd.pci/linux/suse.93/fcpci-suse93-3.11-07.tar.gz).

    As a private corporation our primary focus is market relevance. AVM
    invested more than 10 years of work to make analog services like Fax G3 and
    analog modem emulation available to users of the digital ISDN network. The
    situation is similar for the DSL part of the driver with very complex DSP
    algorithms. To anticipate any "open vs. closed source" discussion:Only a
    handful of companies worldwide have such know-how. With regard to our
    competitive situation, we have to protect our hard-won intellectual
    property and therefore cannot open the closed source part of the driver.

    Kind Regards
    Sven Schmidt

    AVM Audiovisuelles Marketing und Computersysteme GmbH
    Alt-Moabit 95, 10559 Berlin, Germany
    http://www.avm.de





    Greg KH
    <greg@kroah.com>
    An
    05.02.2006 21:53 s.schmidt@avm.de
    Kopie
    linux-kernel@vger.kernel.org,
    opensuse-factory@opensuse.org,
    kkeil@suse.de
    Thema
    Re: 2.6.16 serious consequences /
    GPL_EXPORT_SYMBOL / USB drivers of
    major vendor excluded










    On Fri, Feb 03, 2006 at 05:24:10PM +0100, s.schmidt@avm.de wrote:
    > on January 15th / major change in USB subsystem and GPL_EXPORT_SYMBOL
    > declaration
    > Greg Kroah-Hartman added a Patch to kernel 2.6.15-git12, which
    > substantially changed the USB system.

    Have you asked Greg why he did this?

    Have you asked what the other alternatives are?

    You do know about usbfs/libusb that allows you to write USB drivers in
    userspace that can go at the full speed of the USB bus? Why not redo
    your code to take advantage of this? If you do that, the extra bonus is
    that your drivers will also work on the BSDs and possibly Windows with
    no changes needed (I think libusb works on Windows...)

    > This mail is not intended to provoke a discussion of open vs closed
    source.
    > The only intention of this mail is to make you aware of the consequences
    of
    > such a decision.

    I was not aware of your drivers, but now that you have informed me of
    them, I am willing to work with you to figure out how to resolve this
    issue.

    thanks,

    greg k-h


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