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    SubjectRe: [patch] dynamic char and block devices
    On Wed, 13 Oct 1999, Jeff Garzik wrote:

    > Oliver Xymoron wrote:
    > > I realized when I'd finished this that resource trees were an even better
    > > way to go. It allows us to say things like major x minors a-b use these
    > > fileops while major x minors c-d use these other fileops. It also allows
    > > register_device to be _much_ smarter about how it allocates things - you
    > > can say "please give me a whole major", "please give me 8 minors", any
    > > granularity you'd like. The divide between majors and minors becomes a
    > > continuum. Think of it as CIDR for device space.
    >
    > Very nifty idea. See why I like the new resource code? :)

    Yes. Though it might need a few more primitives to fully realize its
    usefulness. My tinkering to make it more flexible isn't getting anywhere -
    I wrote a find_resource to either find a resource or find its tree
    insertion point, which is now the core of __request_resource. However,
    because the list of siblings is singly-linked, it ended up taking a struct
    resource ***. Too sick to live.

    Linus, would you consider a patch to make resource siblings doubly-linked?
    We could then use the list macros and avoid the pointer to a pointer stuff
    in the current code. Alternately, a tree.h might not be a bad idea.

    > Anyway, something like this seems to imply that you would have to change
    > the prototype of register_chrdev and register_blkdev. Is this correct?

    No, they remain the same. My patch makes those two thin wrappers around a
    generic register_dev function just like your patch does. All my new
    functions take a kdev_t and a device type (block/char). I'd like a future
    kdev_t to include a bit indicating type, which would make this even
    cleaner. Block and char devices work more or less identically from the pov
    of most of the kernel.

    --
    "Love the dolphins," she advised him. "Write by W.A.S.T.E.."


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