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    SubjectRe: [RFC] Add of_path property for all devices with a node
    On 11/6/2014 10:33 PM, Benjamin Herrenschmidt wrote:
    > Hey folks ! This is not (yet) a formal patch submission but...
    >
    > So I've been annoyed lately with having a bunch of devices such as i2c
    > eeproms (for use by VPDs, server world !) and other bits and pieces that
    > I want to be able to identify from userspace, and possibly provide
    > additional data about from FW.
    >
    > Basically, it boils down to correlating the sysfs device with the OF
    > tree device node, so that user space can use device-tree info such as
    > additional "location" or "label" (or whatever else we can come up with)
    > propreties to identify a given device, or get some attributes of use
    > about it, etc...
    >
    > Now, so far, we've done that in some subsystem in a fairly ad-hoc basis
    > using "devspec" properties. For example, PCI creates them if it can
    > correlate the probed device with a DT node. Some powerpc specific busses
    > do that too.
    >
    > However, i2c doesn't and it would be nice to have something more generic
    > since technically any device can have a corresponding device tree node.
    >
    > So I came up with this patch, it seems to work well for me. I'm adding
    > an "of_path" attribute to not conflict with the existing "devspec" one
    > just for the sake of this experiment (plus "devspec" sucks). Long run,
    > we might want to use of_path and leave a "devspec" symlink to of_path on
    > the few busses that currently have devspec (pci and some powerpc
    > specific ones).
    >
    > Comments ?
    >
    > Cheers,
    > Ben.

    If I understand correctly, that information is already available in
    the file uevent. For example, if I apply your patch, at least
    for a simple path, I see the same path name in uevent as in of_path:

    $ cd /sys/devices/soc/f9824900.sdhci
    $ cat of_path
    /soc/sdhci@f9824900
    $ grep OF_FULLNAME uevent | cut -d"=" -f2
    /soc/sdhci@f9824900

    -Frank


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