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    SubjectRe: [PATCH] Open Firmware device tree virtual filesystem

    On Dec 30 2006 15:38, Mitch Bradley wrote:
    > Request for comments.
    > It is similar in some respect to fs/proc/proc_devtree.c , but does
    > not use procfs, nor does it require an intermediate layer of code
    > to create a flattened representation of the device tree.

    NB: openpromfs does not use procfs either. It just happens to be
    mounted somewhere down there.

    > +++ b/Documentation/filesystems/ofwfs.txt
    > +== Property Value Encoding ==
    > +
    > +A regular file in ofwfs contains the exact byte sequence that
    > +comprises the OFW property value. Properties are not reformatted
    > +into text form, so numeric property values appear as binary
    > +integers. While this is inconvenient for viewing, it is generally
    > +easier for programs that read property values, and it means that
    > +Open Firmware documentation about property values applies
    > +directly, without having to separately document an ASCII
    > +transformation (which would have to separately specified for
    > +different kinds of properties).

    I appreciate the ASCII formatting that openpromfs currently does.
    Perhaps, should OFWFS be used, it could offer both?

    > +== Environment Assumptions ==
    > +
    > +The ofwfs code assumes that the Open Firmware client interface
    > +callback can be executed during Linux kernel startup
    > +(specifically, at "core_initcall" time). When ofwfs is
    > +initialized, it copies out the property values, so that subsequent
    > +accesses to the tree do not require callbacks into OFW.

    openpromfs also has many parts read-only, only one object,
    /options/security-password, is writable. Hence caching it once and
    forever seems ok.

    BUT, the eeprom utility may be used to modify values, and if used, I
    would like to see ofwfs show the updated value. openpromfs does it

    15:09 ares:/proc/openprom/options # cat oem-banner?
    15:09 ares:/proc/openprom/options # eeprom 'oem-banner?=true'
    15:09 ares:/proc/openprom/options # cat oem-banner?

    (BTW, why does not openpromfs have it rw?)

    > +== Recommended Mount Point ==
    > +
    > +The recommended mount point for ofwfs is /ofw. (TBD: Should it be
    > +mounted somewhere under /sys instead?)

    Somewhere in /sys/firmware perhaps.

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      Last update: 2006-12-31 15:19    [W:0.022 / U:36.616 seconds]
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