util: mdev: Treat the 'name' sysfs attribute as optional

When commit 3545cbef moved the sysfs attribute reading logic from
_udev.c module to virmdev.c, it had to replace our udev read wrappers
with the ones available from virfile.c. The problem is that the original
logic worked correctly with udev read wrappers which don't return an
error code for a missing attribute, virfile.c readers however - not so
much. Therefore add another parameter to the macro, so we can again
accept the fact that optional attributes may be missing.
Signed-off-by: NErik Skultety <eskultet@redhat.com>
Reviewed-by: NJohn Ferlan <jferlan@redhat.com>

src/util/virmdev.c

@@ -505,10 +505,13 @@ virMediatedDeviceTypeReadAttrs(const char *sysfspath,
     int ret = -1;
     virMediatedDeviceTypePtr tmp = NULL;
 
-#define MDEV_GET_SYSFS_ATTR(attr, dst, cb) \
+#define MDEV_GET_SYSFS_ATTR(attr, dst, cb, optional) \
     do { \
-        if (cb(dst, "%s/%s", sysfspath, attr) < 0) \
-            goto cleanup; \
+        int rc; \
+        if ((rc = cb(dst, "%s/%s", sysfspath, attr)) < 0) { \
+            if (rc != -2 || !optional) \
+                goto cleanup; \
+        } \
     } while (0)
 
     if (VIR_ALLOC(tmp) < 0)
@@ -517,10 +520,12 @@ virMediatedDeviceTypeReadAttrs(const char *sysfspath,
     if (VIR_STRDUP(tmp->id, last_component(sysfspath)) < 0)
         goto cleanup;
 
-    MDEV_GET_SYSFS_ATTR("name", &tmp->name, virFileReadValueString);
-    MDEV_GET_SYSFS_ATTR("device_api", &tmp->device_api, virFileReadValueString);
+    /* @name sysfs attribute is optional, so getting ENOENT is fine */
+    MDEV_GET_SYSFS_ATTR("name", &tmp->name, virFileReadValueString, true);
+    MDEV_GET_SYSFS_ATTR("device_api", &tmp->device_api,
+                        virFileReadValueString, false);
     MDEV_GET_SYSFS_ATTR("available_instances", &tmp->available_instances,
-                        virFileReadValueUint);
+                        virFileReadValueUint, false);
 
 #undef MDEV_GET_SYSFS_ATTR