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    SubjectRe: devfs vs udev, thoughts from a devfs user
    On Sat, Feb 14, 2004 at 12:51:11AM -0800, Mike Bell wrote:
    > On Fri, Feb 13, 2004 at 01:19:20PM -0800, Greg KH wrote:
    > > > That's a pretty minor difference, from the kernel's point of view. It's
    > > > basically putting the same numbers in different fields.
    > >
    > > Heh, that's a HUGE difference!
    > Only from userspace's point of view. To the kernel, it's basically the
    > same thing.

    Woah, no this is NOT true. If you continue to this this, then this
    discussion is going to go no where.

    Remember, the "dev" file in sysfs is just another attribute for the
    device. Just like a serial number or product id. A device node would
    be a totally different thing. See all of the other messages from others
    about why this is true.

    > Now keeping in mind again that I'm not advocating putting device nodes
    > into sysfs, what about a little thought experiment. Supposing you did
    > replace sysfs's major:minor text file with a real device node

    Stop right there and go read the archives for why we are not going to do
    this. This has been discussed a lot.

    > Now, here's a question. What's wrong with taking those and splitting
    > them into a new filesystem?

    Because then you have devfs, which is not what we are trying to do here.

    It seems that you are insisting that we have to make a devfs. Great,
    have fun, use the devfs we already have.

    > As I see it, part of the reason procfs
    > became such a nightmare was because people thought there could be only
    > one kernel-generated filesystem and put everything in there.

    Not true. procfs got to be a mess for lots of other reasons (lack of
    control, no other options, etc...)

    > Linux
    > is moving a lot of the silly magic values out of proc and into sysfs
    > where they make more sense. Great! But what about stuff that doesn't
    > really fit into sysfs as it is right now? Should we take sysfs's clean
    > interface and extend it with special cases until it's the ugly mess proc
    > is?

    No, and I'm not advocating that at all, and never have. That's not the
    point here.

    > Or leave everything that doesn't fit cleanly into sysfs in proc,
    > making proc a sort of special-cases wasteland?

    No, go make your own fs if that's what is needed. See the IBM service
    processor driver filesystem for an example of something like this.

    > Alternativly, why not say that there doesn't need to be just one or two
    > kernel-exported filesystems, and instead make a sort of library for
    > exporting kernel information via fake filesystems (I can't remember, has
    > this already been done?)

    already been done, see the libfs code. I don't understand what this has
    to do with udev though....

    > I'm not a kernel hacker

    Stop. Go read Especially pay attention to
    the section "Back-seat coders are bad." I specifically like the lines:

    If you don't know how to code, then you don't know how to design
    the software either. Period. You can only cause trouble.

    So my main point is, I don't know what you are arguing anymore. If you
    don't like udev, and for some reason think that devfs and devfsd can
    provide you a stable, secure, and PERSISTENT device naming system, then
    fine, go use devfs.

    The rest of us will be over here using udev.

    (Remember you still haven't told me how you are going to name your scsi
    disk and USB printer in a persistent manner no matter how they are
    discovered using devfsd.)

    > How do you figure that's free? hotplug's a great feature, nothing
    > against it, but as far as I know the vast majority of installations
    > aren't making use of it right now.

    Hint, I don't know of ANY distro that does not enable CONFIG_HOTPLUG
    that is not a embedded distro. That's why I call it "free". It has so
    many other benefits that people can no longer turn it off and expect
    their systems to work "nicely".

    In conclusion, if you have any problems with udev, how it works, how it
    is configured, etc., I'm very glad to hear them and help you through it.
    But if you just want to complain about how we all should be using devfs
    and devfsd instead of sysfs and udev, you are going to get no where with


    greg k-h
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