libnvdimm, nvdimm: dimm driver and base libnvdimm device-driver infrastructure

* Implement the device-model infrastructure for loading modules and
  attaching drivers to nvdimm devices.  This is a simple association of a
  nd-device-type number with a driver that has a bitmask of supported
  device types.  To facilitate userspace bind/unbind operations 'modalias'
  and 'devtype', that also appear in the uevent, are added as generic
  sysfs attributes for all nvdimm devices.  The reason for the device-type
  number is to support sub-types within a given parent devtype, be it a
  vendor-specific sub-type or otherwise.

* The first consumer of this infrastructure is the driver
  for dimm devices.  It simply uses control messages to retrieve and
  store the configuration-data image (label set) from each dimm.

Note: nd_device_register() arranges for asynchronous registration of
      nvdimm bus devices by default.

Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Neil Brown <neilb@suse.de>
Acked-by: Christoph Hellwig <hch@lst.de>
Tested-by: Toshi Kani <toshi.kani@hp.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

include/linux/libnvdimm.h

@@ -30,6 +30,7 @@ enum {
 
 extern struct attribute_group nvdimm_bus_attribute_group;
 extern struct attribute_group nvdimm_attribute_group;
+extern struct attribute_group nd_device_attribute_group;
 
 struct nvdimm;
 struct nvdimm_bus_descriptor;
@@ -71,4 +72,5 @@ u32 nd_cmd_in_size(struct nvdimm *nvdimm, int cmd,
 u32 nd_cmd_out_size(struct nvdimm *nvdimm, int cmd,
 		const struct nd_cmd_desc *desc, int idx, const u32 *in_field,
 		const u32 *out_field);
+int nvdimm_bus_check_dimm_count(struct nvdimm_bus *nvdimm_bus, int dimm_count);
 #endif /* __LIBNVDIMM_H__ */