qom: Drop object_property_set_description() parameter @errp

object_property_set_description() and
object_class_property_set_description() fail only when property @name
is not found.

There are 85 calls of object_property_set_description() and
object_class_property_set_description().  None of them can fail:

* 84 immediately follow the creation of the property.

* The one in spapr_rng_instance_init() refers to a property created in
  spapr_rng_class_init(), from spapr_rng_properties[].

Every one of them still gets to decide what to pass for @errp.

51 calls pass &error_abort, 32 calls pass NULL, one receives the error
and propagates it to &error_abort, and one propagates it to
&error_fatal.  I'm actually surprised none of them violates the Error
API.

What are we gaining by letting callers handle the "property not found"
error?  Use when the property is not known to exist is simpler: you
don't have to guard the call with a check.  We haven't found such a
use in 5+ years.  Until we do, let's make life a bit simpler and drop
the @errp parameter.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20200505152926.18877-8-armbru@redhat.com>
[One semantic rebase conflict resolved]

1 files changed, 3 insertions, 6 deletions

diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
index f660070..2f94061 100644
--- a/hw/s390x/s390-virtio-ccw.c
+++ b/hw/s390x/s390-virtio-ccw.c
@@ -731,24 +731,21 @@ static inline void s390_machine_initfn(Object *obj)
                              machine_get_aes_key_wrap,
                              machine_set_aes_key_wrap, NULL);
     object_property_set_description(obj, "aes-key-wrap",
-            "enable/disable AES key wrapping using the CPACF wrapping key",
-            NULL);
+            "enable/disable AES key wrapping using the CPACF wrapping key");
     object_property_set_bool(obj, true, "aes-key-wrap", NULL);
 
     object_property_add_bool(obj, "dea-key-wrap",
                              machine_get_dea_key_wrap,
                              machine_set_dea_key_wrap, NULL);
     object_property_set_description(obj, "dea-key-wrap",
-            "enable/disable DEA key wrapping using the CPACF wrapping key",
-            NULL);
+            "enable/disable DEA key wrapping using the CPACF wrapping key");
     object_property_set_bool(obj, true, "dea-key-wrap", NULL);
     object_property_add_str(obj, "loadparm",
             machine_get_loadparm, machine_set_loadparm, NULL);
     object_property_set_description(obj, "loadparm",
             "Up to 8 chars in set of [A-Za-z0-9. ] (lower case chars converted"
             " to upper case) to pass to machine loader, boot manager,"
-            " and guest kernel",
-            NULL);
+            " and guest kernel");
 }
 
 static const TypeInfo ccw_machine_info = {