[PATCH] libnvdimm, region: hide persistence_domain when unknown

[Dan Williams]

Similar to other region attributes, do not emit the persistence_domain
attribute if its contents are empty.

Fixes: 96c3a239054a ("libnvdimm: expose platform persistence attr...")
Cc: Dave Jiang <dave.ji...@intel.com>
Signed-off-by: Dan Williams <dan.j.willi...@intel.com>
---
 drivers/nvdimm/region_devs.c |    7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
index e6d01911e092..a8e9d428c0a5 100644
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -593,6 +593,13 @@ static umode_t region_visible(struct kobject *kobj, struct 
attribute *a, int n)
                        return 0;
        }
 
+       if (a == &dev_attr_persistence_domain.attr) {
+               if ((nd_region->flags & (BIT(ND_REGION_PERSIST_CACHE)
+                                       | BIT(ND_REGION_PERSIST_MEMCTRL))) == 0)
+                       return 0;
+               return a->mode;
+       }
+
        if (a != &dev_attr_set_cookie.attr
                        && a != &dev_attr_available_size.attr)
                return a->mode;