Re: + pnp-mpu401-adjust-pnp_register_driver-signature.patch added to -mm tree

["Bjorn Helgaas" <bjorn.helgaas@hp.com>]

>> This series of patches removes the assumption that pnp_register_driver()
>> returns the number of devices claimed.  Returning the count is
>> unreliable
>> because devices may be hot-plugged in the future.  (Many devices don't
>> support
>> hot-plug, of course, but PNP in general does.)
>
> Huh?
>
> How do onboard devices or ISA plug and play devices support hot-plug?
>
> Or what devices supported by the pnp subsystem support hot-plug?

I don't know for sure whether ISAPNP or PNPBIOS support hot-plug,
but ACPI does, and ACPI devices are being integrated into the
PNP subsystem via PNPACPI.

One example is HP sx2000 hardware that supports hot-plug of cells.
Each cell contains CPUs, memory, I/O bridges, and some miscellaneous
hardware like on-board serial devices.  All this stuff is described
by ACPI, and we'd like to use PNP drivers like 8250_pnp.c when we can.