cxl/core: Move memdev management to core

The motivation for moving cxl_memdev allocation to the core (beyond
better file organization of sysfs attributes in core/ and drivers in
cxl/), is that device lifetime is longer than module lifetime. The cxl_pci
module should be free to come and go without needing to coordinate with
devices that need the text associated with cxl_memdev_release() to stay
resident. The move fixes a use after free bug when looping driver
load / unload with CONFIG_DEBUG_KOBJECT_RELEASE=y.

Another motivation for disconnecting cxl_memdev creation from cxl_pci is
to enable other drivers, like a unit test driver, to registers memdevs.

Fixes: b39cb1052a5c ("cxl/mem: Register CXL memX devices")
Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/162792540495.368511.9748638751088219595.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
index 0cd463d..25345ec 100644
--- a/drivers/cxl/cxlmem.h
+++ b/drivers/cxl/cxlmem.h
@@ -28,12 +28,6 @@
 	(FIELD_GET(CXLMDEV_RESET_NEEDED_MASK, status) !=                       \
 	 CXLMDEV_RESET_NEEDED_NOT)
 
-/*
- * An entire PCI topology full of devices should be enough for any
- * config
- */
-#define CXL_MEM_MAX_DEVS 65536
-
 /**
  * struct cdevm_file_operations - devm coordinated cdev file operations
  * @fops: file operations that are synchronized against @shutdown
@@ -63,6 +57,15 @@ struct cxl_memdev {
 	int id;
 };
 
+static inline struct cxl_memdev *to_cxl_memdev(struct device *dev)
+{
+	return container_of(dev, struct cxl_memdev, dev);
+}
+
+struct cxl_memdev *
+devm_cxl_add_memdev(struct device *host, struct cxl_mem *cxlm,
+		    const struct cdevm_file_operations *cdevm_fops);
+
 /**
  * struct cxl_mem - A CXL memory device
  * @pdev: The PCI device associated with this CXL device.