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    SubjectRe: VPD in sysfs
    Matthew Wilcox wrote:
    > I've been sent a patch that reads some VPD from the Symbios NVRAM and
    > displays it in sysfs. I'm not sure whether the way the author chose
    > to present it is the best. They put it in 0000:80:01.0/host0/vpd_name
    > which seems a bit too scsi-specific and insufficiently forward-looking
    > (I bet we want to expose more VPD data than that in the future, so we
    > should probably use a directory).
    > I actually have a feeling (and please don't kill me for saying this), that
    > we should add a struct vpd * to the struct device. Then we need something
    > like the drivers/base/power/sysfs.c file (probably drivers/base/vpd.c)
    > that takes care of adding vpd to each device that wants it.
    > Thoughts? Since there's at least four and probably more ways of getting
    > at VPD, we either need to fill in some VPD structs at initialisation or
    > have some kind of vpd_ops that a driver can fill in so the core can get
    > at the data.

    I like this idea. Certain VPD parameters are standard across SCSI devices,
    so they could be shown in a standard way.

    Not sure on the format of vpd_ops, _but_ getting the VPD data via
    the EVPD bit in INQUIRY, could be pretty standard method, so that
    if the LLDD doesn't set vpd_ops, they could be set to point to
    the (this) generic way*. (The LLDD can snoop the INQUIRY data if
    it wishes to, for further control.)

    *I.e. the vpd_ops method(s) would be generic enough to abstract out
    the actual method of getting the VPD...

    Certainly, providing a vpd node in sysfs would help user level
    apps id devices more easily. This could also be used by multipathing
    sofware and other apps. I think it's a good idea.


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