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    SubjectRe: Documentation for sysfs, hotplug, and firmware loading.
    On Mon, 23 Jul 2007, Rob Landley wrote:
    > On Saturday 21 July 2007 8:14:41 am Bodo Eggert wrote:
    > > Greg KH <> wrote:
    > > > On Fri, Jul 20, 2007 at 08:21:39PM -0400, Rob Landley wrote:
    > > >> I'm not trying to document /sys/devices. I'm trying to document
    > > >> hotplug, populating /dev, and things like firmware loading that fall out
    > > >> of that. This requires use of sysfs, and I'm only trying to document as
    > > >> much of sysfs as you need to do that.
    > > >
    > > > Like I stated before, you do not need to even have sysfs mounted to have
    > > > a dynamic /dev.
    > > >
    > > > And why do you need to document populating /dev dynamically? udev
    > > > already solves this problem for you, it's not like people are going off
    > > > and reinventing udev for their own enjoyment would not at least look at
    > > > how it solves this problem first.
    > >
    > > Turning your words around, you get: "Whatever one of these programs does
    > > documents how dynamic devices should be handled." If this is true, any
    > > change that makes one of these programs break is a kernel bug.
    > >
    > > Besides that: How am I supposed to be able to correctly change udev if
    > > there is no document telling me what would work and what happens to
    > > work by accident?
    > You aren't expected to. Remember that udev and sysfs are written by the same
    > people, working together off-list. They're free to break the exported data
    > format on a whim, because they write the code at both ends and fundamentally
    > they're talking to themselves. They honestly say you can't expect a new
    > kernel to work with an old udev, and they say it with a straight face. (To
    > me, this sounds like saying you can't expect a new kernel to work with an old
    > version of ps, because of /proc.)
    > Documentation is a threat to this way of working, because it would impose
    > restrictions on them. A spec is only of use if you introduce the radical
    > idea that the information exported by sysfs exists for some purpose _other_
    > than simply to provide udev with information (and a specific version of udev
    > matched to that kernel version, at that).

    And having no documentation is, as you can see in this thread, a threat to
    open software. Having exactly one blob of software, and being left on your
    own once you change a bit, is one step away from having a binary only module.

    > > > To do otherwise would be foolish :)
    > >
    > > Some people like to fool around and create even smaller wheels.
    > > E.g. I'm changing the ACPI button driver to just call Ctrl_alt_del
    > > in order not to have an extra process running and free 0.2 % of my RAM.
    > When I started looking at udev in 2005, it was a disaster. My commentary at
    > the time is at and the relevant bit is:


    > And so I made mdev, a utility which populated /dev _with_ a config file in 7k.
    > Greg's upset I didn't just patch udev to remove libsysfs, remove the
    > duplicated klibc code, remove the gratuitous database, remove the
    > overcomplicated config file parser (with rules compiler), and so on. They're
    > boggling that I could ever have been unhappy with the One True Project to
    > populate /dev.

    I see, we agree on this point. Besides that, I like to see the steps to be
    done, instead of having a letter sent to a voodoo doctor in Africa (called
    udev) and getting back a magic spell to be chanted on my system (unless
    he just pokes some voodoo doll).
    Top 100 things you don't want the sysadmin to say:
    87. Sorry, the new equipment didn't get budgetted.
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