enabled and failed flags in acpi_memory_info

[Toshi Kani <toshi.kani@hp.com>]

Hi Wen,

I have a question about the change you made in commit 65479472 in
acpi_memhotplug.c.  This change seems to require that
acpi_memory_enable_device() calls add_memory() to add all memory ranges
represented by memory device objects at boot-time, and keep the results
be used for hot-remove.  

If I understand it right, this add_memory() call fails with EEXIST at
boot-time since all memory ranges should have been added from EFI memory
table (or e820) already.  This results all memory ranges be marked as !
enabled & !failed.  I think this means that we cannot hot-delete any
memory ranges presented at boot-time since acpi_memory_remove_memory()
only calls remove_memory() when the enabled flag is set.  Is that
correct?  If so, why do we need such restriction?

In addition, as part of RFC patchset of proposed hotplug framework below
(well, this is why I am wondering this... :), I simply called
add_memory() and remove_memory() for the ranges requested for hot-add /
hot-delete.  It does not call add_memory() at boot-time and set the
enabled & failed flags.  But it does not eject memory when
remove_memory() failed, either.  Do you see any problems with this
approach? 
https://lkml.org/lkml/2012/12/12/457

Thanks,
-Toshi