device-dax: Introduce bus + driver model

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>

1 files changed, 2 insertions, 4 deletions

diff --git a/drivers/dax/dax-private.h b/drivers/dax/dax-private.h
index 620c3f4eefe7..c3a121700837 100644
--- a/drivers/dax/dax-private.h
+++ b/drivers/dax/dax-private.h
@@ -20,10 +20,8 @@
 struct dax_device;
 struct dax_device *inode_dax(struct inode *inode);
 struct inode *dax_inode(struct dax_device *dax_dev);
-
-/* temporary until devm_create_dax_dev moves to bus.c */
-extern const struct attribute_group *dax_attribute_groups[];
-void unregister_dev_dax(void *dev);
+int dax_bus_init(void);
+void dax_bus_exit(void);
 
 /**
  * struct dax_region - mapping infrastructure for dax devices