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    SubjectRe: CML2 1.0.0 release announcement
    Alan Cox <>:
    > Multiple layers of is a feature

    I disagree, because I've seen what happens when we go to a single-apex tree.
    But you could persuade me otherwise. What's your reason for believing this?

    The problem with having multiple apices of the configuration tree (as I see
    it) is that we often ended up duplicating configuration code for things that
    aren't actually port-dependent but rather depend on other things such as
    supported bus types (ISA, PCA, PCMCIA, etc.). This is a particularly big
    issue with network cards and disk controllers.

    The duplicated code then starts to skew. You end up with lots of features
    (especially drivers) that could be supported across architectures but aren't,
    simply because port maintainers are focused on their own trees and don't look
    at what's going on in the others.

    A multiple-apex tree also tends to pull the configuration questions downwards
    from policy (e.g "Parallel-port support?") towards hardware-specific,
    platform-specific questions ("Atari parallel-port hardware?") By designing
    the configuration rules for CML2 as a single-apex tree, I'm trying to
    move the questions upwards and have derivations in the rules file handle
    distributing that information to a lower level.

    For example, instead of a bunch of parallel questions like this in a
    multiple-apex tree:

    PARPORT 'Parallel port support'
    PARPORT_PC 'PC-style hardware'
    PARPORT_PC_PCMCIA 'Support for PCMCIA management for PC-style ports'
    PARPORT_ARC 'Archimedes hardware'
    PARPORT_AMIGA 'Amiga builtin port'
    PARPORT_MFC3 'Multiface III parallel port'
    PARPORT_ATARI 'Atari hardware'
    PARPORT_SUNBPP 'Sparc hardware'

    I'm trying to move us towards having *one* question and a bunch of
    well-hidden intelligence about what it implies:

    PARPORT 'Parallel port support'
    derive PARPORT_PC from PARPORT and X86
    derive PARPORT_ARC from PARPORT and ARC
    derive PARPORT_SUNBPP from PARPORT and SUN
    <a href="">Eric S. Raymond</a>

    Government is actually the worst failure of civilized man. There has
    never been a really good one, and even those that are most tolerable
    are arbitrary, cruel, grasping and unintelligent.
    -- H. L. Mencken
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