conf: introduce parser feature flags

To avoid having to forbid new features added to domain XML in post parse
callbacks for individual hypervisor drivers the feature flag mechanism
will allow to add a central check that will be disabled for the drivers
that will add support.

As a first example flag, the 'hasWideSCSIBus' is converted to the new
bitmap.

src/conf/domain_conf.c

@@ -4038,18 +4038,21 @@ virDomainHostdevAssignAddress(virDomainXMLOptionPtr xmlopt,
 {
     int next_unit = 0;
     unsigned controller = 0;
+    unsigned int max_unit;
     size_t i;
     int ret;
 
+    if (xmlopt->config.features & VIR_DOMAIN_DEF_FEATURE_WIDE_SCSI)
+        max_unit = SCSI_WIDE_BUS_MAX_CONT_UNIT;
+    else
+        max_unit = SCSI_NARROW_BUS_MAX_CONT_UNIT;
+
     for (i = 0; i < def->ncontrollers; i++) {
         if (def->controllers[i]->type != VIR_DOMAIN_CONTROLLER_TYPE_SCSI)
             continue;
 
         controller++;
-        ret = virDomainControllerSCSINextUnit(def,
-                                              xmlopt->config.hasWideSCSIBus ?
-                                              SCSI_WIDE_BUS_MAX_CONT_UNIT :
-                                              SCSI_NARROW_BUS_MAX_CONT_UNIT,
+        ret = virDomainControllerSCSINextUnit(def, max_unit,
                                               def->controllers[i]->idx);
         if (ret >= 0) {
             next_unit = ret;
@@ -5861,7 +5864,7 @@ virDomainDiskDefAssignAddress(virDomainXMLOptionPtr xmlopt,
 
         def->info.type = VIR_DOMAIN_DEVICE_ADDRESS_TYPE_DRIVE;
 
-        if (xmlopt->config.hasWideSCSIBus) {
+        if (xmlopt->config.features & VIR_DOMAIN_DEF_FEATURE_WIDE_SCSI) {
             /* For a wide SCSI bus we define the default mapping to be
              * 16 units per bus, 1 bus per controller, many controllers.
              * Unit 7 is the SCSI controller itself. Therefore unit 7

src/conf/domain_conf.h

@@ -2407,6 +2407,11 @@ typedef bool (*virDomainObjListACLFilter)(virConnectPtr conn,
                                           virDomainDefPtr def);
 
 
+typedef enum {
+    VIR_DOMAIN_DEF_FEATURE_WIDE_SCSI = (1 << 0),
+} virDomainDefFeatures;
+
+
 /* This structure holds various callbacks and data needed
  * while parsing and creating domain XMLs */
 typedef struct _virDomainXMLOption virDomainXMLOption;
@@ -2438,7 +2443,7 @@ struct _virDomainDefParserConfig {
     virFreeCallback privFree;
 
     /* data */
-    bool hasWideSCSIBus;
+    unsigned int features; /* virDomainDefFeatures */
     unsigned char macPrefix[VIR_MAC_PREFIX_BUFLEN];
 };
 

src/vmx/vmx.c

@@ -548,10 +548,10 @@ virVMXDomainDevicesDefPostParse(virDomainDeviceDefPtr dev ATTRIBUTE_UNUSED,
 }
 
 static virDomainDefParserConfig virVMXDomainDefParserConfig = {
-    .hasWideSCSIBus = true,
     .macPrefix = {0x00, 0x0c, 0x29},
     .devicesPostParseCallback = virVMXDomainDevicesDefPostParse,
     .domainPostParseCallback = virVMXDomainDefPostParse,
+    .features = VIR_DOMAIN_DEF_FEATURE_WIDE_SCSI,
 };
 
 static void