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    SubjectRe: Large device numbers (was Re: disk naming proposal & devfs)
    You are also correct.  It is being implemented as a solution to 
    just about any problem presented in the current system. See
    Richards FAQ on the topic for the definitive view, he is writing
    the code after all.

    I just happen to know which solutions interest me most.

    On Tue, 13 Jan 1998, Ian Burrell wrote:

    > >
    > > Various problems related to the current indirect device referencing
    > > scheme, including (but not necessarily limited to):
    > > -8bit minors,
    > > -major/minor table lookup times
    > > -filesystem rewriting necessary to go to 16 or 32 bit minors.
    > > -major number conflict resolution
    > >
    > I thought devfs was a solution to the problems of large directories
    > and dynamic creation of device files. There really should be a common
    > system for going from device number to device that is independent of
    > whether it is an on-disk device node or purely virtual inode. The
    > device registration could be made distinct from the inodes and
    > directories entry in devfs and normal devices nodes. Opening a file
    > goes filename -> dentry -> inode -> dev_t -> device. A new lookup
    > would be needed for dev_t to device driver.
    > The easy way to split 64-bit device numbers in half and use the 32-bit
    > major number to identify the device driver and the 32-bit minor number
    > used to identify the specific device. Drivers would register
    > themselves with the driver table, and the minor number and canonical
    > name with device table/devfs.
    > A better way might be use the entire 64-bit value as the device id and
    > scrap the major/minor separation. Then the driver is identified by
    > variable-length prefix. Overlapping drivers could be accomplished
    > with a longest-matching-prefix search. This would be inefficient but
    > could be speeded up by caching the resolved devices in inodes.
    > - Ian
    > --
    > -- Ian Burrell == **
    > <URL:>
    > All programmers are playwrights and all computers are lousy actors.

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