OLS 2001 coverage
Hotplugging support in the Linux kernel
Due to a lunch meeting which went a bit overlong, your correspondent missed
much of Greg Kroah-Hartman's session on hotplugging support. It was not
one of the better sessions to miss; hotplugging is a, well, hot topic. The
nature of hardware is increasingly dynamic, and the Linux kernel must learn
to adapt to a world that can change at any time.
Greg gave what must have been an interesting talk on how the
/sbin/hotplug tool works, automatic determination of the proper
driver modules to load, etc. Toward the end, however, he was talking about
the work that still needs to be done, with an eye toward the 2.5 kernel.
Future work includes:
- SCSI hotplug support. The SCSI layer is likely to get thrashed up,
again, in 2.5. Prediction: everybody will still complain about it.
- Better PCMCIA support. PCMCIA currently has its own, completely
different way of dealing with dynamic devices; much has been learned
from the PCMCIA approach, but there seems to be a desire to get rid of
it and move PCMCIA into the new hotplug mechanism.
- Hotplug IDE devices. A patch is apparently in circulation.
- PCI and CompactPCI devices; patches exist for these as well.
- Laptop docking stations.
- Hotplug CPUs; the CPU patch has been out there for a while.
- Better distribution support. The hotplug stuff is very new, of
course, and uptake by the distributions remains somewhat spotty. SuSE
was named as being a special goal for the hotplug people.
The most interesting thing, perhaps, came right at the end, when Greg
raised the point that ACPI may eventually obsolete the entire Linux hotplug
effort. As ACPI gets the basic configuration and power management issues
taken care of, hotplug management will increasingly come within their
sites. Of course, as LWN has covered
elsewhere, not everybody is happy with the design of ACPI. There could
be an interesting fight in the future.
More information on Linux and hotplugging at linux-hotplug.sf.net.
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