OpenFirmware devices and hotplug events

Nathan Lynch nathanl at
Thu Mar 18 09:24:07 EST 2004

Dave Hansen wrote:
>>If not explicitly specified, the decision about which drc index to add
>>or remove is made by a userspace program which is invoked by the
>>machine's management console (the HMC).  So that would break.
> Really?  I didn't know that the HMC had any access to the OS on the
> machines that it is controlling, other than through hypervisor events.
> Can you give me a better description of what this interface is, or how
> it works?

I'll do my best, hopefully someone will jump in and correct me if I get
anything wrong.  I believe the HMC communicates with both the hypervisor
and the LPAR in question for such an operation.  There is a daemon which
runs on the LPAR, and the HMC communicates commands to it via the local
network.  That daemon invokes the program which I was talking about,
which goes about acquiring or releasing drc indexes as well as
hotplugging the corresponding devices.  The daemon reports the results
back to the HMC.  Hopefully this description isn't too vague; the
software I'm describing is not released yet for Linux.

> We are talking about a userspace program running on the LPAR or full
> system, not on the HMC, right?



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