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    SubjectRe: DEVFSv50 and /dev/fb? (or /dev/fb/? ???)
    kragen@pobox.com writes:
    > I must have missed the explanation of how autoloading of device-driver
    > modules works with devfs. If a device is to be automatically loaded
    > and configured when someone tries to access it, and devfs creates names
    > in /dev as devices are loaded and configured, then how do you try to
    > access the unloaded, unconfigured device?

    When you attempt to access a device node which isn't there (say
    "ide/cd/c0b0t0u0") then for each path component that doesn't exist,
    devfs sends that to kmod. Thus, potentially, you have have the
    following sequence of strings sent to kmod: "ide", "ide/cd",
    "ide/cd/c0b0t0u0".
    In practice, people will have IDE configured into their kernel, so the
    "ide" component is already there. Then the "ide/cd" string will be
    sent to kmod. Now, if you have

    # /etc/modules.conf
    alias ide/cd ide-cd

    then the ide-cd module will be loaded as required. Then the module
    will detect your CD-ROM and will also register the "c0b0t0u0"
    entry. So in general only one request is made to kmod: "ide/cd".

    Something to keep in mind here is that while device entries don't
    appear/exist at first, an explicit lookup of the inode (any syscall
    that provides a pathname) will trigger kmod. So it all just magically
    works.

    Regards,

    Richard....
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