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]

2 files changed, 11 insertions, 14 deletions

diff --git a/backends/hostmem-memfd.c b/backends/hostmem-memfd.c
index 74ba987..5991f31 100644
--- a/backends/hostmem-memfd.c
+++ b/backends/hostmem-memfd.c
@@ -144,23 +144,20 @@ memfd_backend_class_init(ObjectClass *oc, void *data)
                                        memfd_backend_set_hugetlb,
                                        &error_abort);
         object_class_property_set_description(oc, "hugetlb",
-                                              "Use huge pages",
-                                              &error_abort);
+                                              "Use huge pages");
         object_class_property_add(oc, "hugetlbsize", "int",
                                   memfd_backend_get_hugetlbsize,
                                   memfd_backend_set_hugetlbsize,
                                   NULL, NULL, &error_abort);
         object_class_property_set_description(oc, "hugetlbsize",
-                                              "Huge pages size (ex: 2M, 1G)",
-                                              &error_abort);
+                                              "Huge pages size (ex: 2M, 1G)");
     }
     object_class_property_add_bool(oc, "seal",
                                    memfd_backend_get_seal,
                                    memfd_backend_set_seal,
                                    &error_abort);
     object_class_property_set_description(oc, "seal",
-                                          "Seal growing & shrinking",
-                                          &error_abort);
+                                          "Seal growing & shrinking");
 }
 
 static const TypeInfo memfd_backend_info = {
diff --git a/backends/hostmem.c b/backends/hostmem.c
index 327f9ee..946d176 100644
--- a/backends/hostmem.c
+++ b/backends/hostmem.c
@@ -465,46 +465,46 @@ host_memory_backend_class_init(ObjectClass *oc, void *data)
         host_memory_backend_get_merge,
         host_memory_backend_set_merge, &error_abort);
     object_class_property_set_description(oc, "merge",
-        "Mark memory as mergeable", &error_abort);
+        "Mark memory as mergeable");
     object_class_property_add_bool(oc, "dump",
         host_memory_backend_get_dump,
         host_memory_backend_set_dump, &error_abort);
     object_class_property_set_description(oc, "dump",
-        "Set to 'off' to exclude from core dump", &error_abort);
+        "Set to 'off' to exclude from core dump");
     object_class_property_add_bool(oc, "prealloc",
         host_memory_backend_get_prealloc,
         host_memory_backend_set_prealloc, &error_abort);
     object_class_property_set_description(oc, "prealloc",
-        "Preallocate memory", &error_abort);
+        "Preallocate memory");
     object_class_property_add(oc, "prealloc-threads", "int",
         host_memory_backend_get_prealloc_threads,
         host_memory_backend_set_prealloc_threads,
         NULL, NULL, &error_abort);
     object_class_property_set_description(oc, "prealloc-threads",
-        "Number of CPU threads to use for prealloc", &error_abort);
+        "Number of CPU threads to use for prealloc");
     object_class_property_add(oc, "size", "int",
         host_memory_backend_get_size,
         host_memory_backend_set_size,
         NULL, NULL, &error_abort);
     object_class_property_set_description(oc, "size",
-        "Size of the memory region (ex: 500M)", &error_abort);
+        "Size of the memory region (ex: 500M)");
     object_class_property_add(oc, "host-nodes", "int",
         host_memory_backend_get_host_nodes,
         host_memory_backend_set_host_nodes,
         NULL, NULL, &error_abort);
     object_class_property_set_description(oc, "host-nodes",
-        "Binds memory to the list of NUMA host nodes", &error_abort);
+        "Binds memory to the list of NUMA host nodes");
     object_class_property_add_enum(oc, "policy", "HostMemPolicy",
         &HostMemPolicy_lookup,
         host_memory_backend_get_policy,
         host_memory_backend_set_policy, &error_abort);
     object_class_property_set_description(oc, "policy",
-        "Set the NUMA policy", &error_abort);
+        "Set the NUMA policy");
     object_class_property_add_bool(oc, "share",
         host_memory_backend_get_share, host_memory_backend_set_share,
         &error_abort);
     object_class_property_set_description(oc, "share",
-        "Mark the memory as private to QEMU or shared", &error_abort);
+        "Mark the memory as private to QEMU or shared");
     object_class_property_add_bool(oc, "x-use-canonical-path-for-ramblock-id",
         host_memory_backend_get_use_canonical_path,
         host_memory_backend_set_use_canonical_path, &error_abort);