In support of multiple device-dax instances per device-dax-region and
allowing the 'kmem' driver to attach to dax-instances instead of the
current device-node access, convert the dax sub-system from a class to a
bus. Recall that the kmem driver takes reserved / special purpose
memories and assigns them to be managed by the core-mm.
Aside from the fact the device-dax instances are registered and probed
on a bus, two other lifetime-management changes are made:
1/ Delay attaching a cdev until driver probe time
2/ A new run_dax() helper is introduced to allow restoring dax-operation
after a kill_dax() event. So, at driver ->probe() time we run_dax()
and at ->remove() time we kill_dax() and invalidate all mappings.
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Towards eliminating the dax_class, move the dax-device-attribute
enabling to a new bus.c file in the core. The amount of code
thrash of sub-sequent patches is reduced as no logic changes are made,
just pure code movement.
A temporary export of unregister_dex_dax() and dax_attribute_groups is
needed to preserve compilation, but those symbols become static again in
a follow-on patch.
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
