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    SubjectRe: Mounting a in-ROM filesystem efficiently
    Followup to:  <>
    By author: Thomas Capricelli <>
    In newsgroup:
    > Hello,
    > I'm looking for a way to put a filesystem into ROM.
    > Seems pretty trivial, isn't it ?
    > My understanding is (the way initrd does, and the way I do as of today)
    > * create a RAMDISK
    > * loads the data into ramdisk
    > * mount the ramdisk
    > problem is that I don't want to waste the RAM as the data in the ROM is
    > already in the address space. (it's an embedded system, btw)
    > Speed is not an issue here. ROM access might be slower than RAM, it will
    > always be so much quicker than a disk access. (wrong?)

    Frequently wrong. Depending on the interface, ROM can be just
    unbelievably slow.

    > Ideally, i would give address/length of the fs in ROM to a function, and I
    > would get a ramdisk configured to read its data exactly there, and not in
    > ram.

    The right thing for you to do is to write a block device driver, and
    then mount that block device like any order device. Your in-use data
    will be copied to RAM (i.e. cached), but it can be dropped and
    re-fetched as necessary. This should be the desired behaviour.

    <> at work, <> in private!
    "Unix gives you enough rope to shoot yourself in the foot." <>
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