[infiniband] Allow MAD handlers to indicate response via return value

Now that MAD handlers no longer return a status code, we can allow
them to return a pointer to a MAD structure if and only if they want
to send a response.  This provides a more natural and flexible
approach than using a "response method" field within the handler's
descriptor.

src/include/gpxe/ib_gma.h

 	uint8_t class_version;
 	/** Method */
 	uint8_t method;
-	/** Response method, or zero */
-	uint8_t resp_method;
 	/** Attribute (in network byte order) */
 	uint16_t attr_id;
 	/** Handle attribute
 	 *
-	 * @v gma	General management agent
-	 * @v mad	MAD
-	 *
-	 * The handler should modify the MAD as applicable.  If the
-	 * handler returns with a non-zero value in the MAD's @c
-	 * method field, it will be sent as a response.
+	 * @v gma		General management agent
+	 * @v mad		MAD
+	 * @ret response	MAD response, or NULL to send no response
 	 */
-	void ( * handle ) ( struct ib_gma *gma, union ib_mad *mad );
+	union ib_mad * ( * handle ) ( struct ib_gma *gma, union ib_mad *mad );
 };
 
 /** GMA attribute handlers */

src/net/infiniband/ib_gma.c

  *****************************************************************************
  */
 
+/**
+ * Construct directed route response, if necessary
+ *
+ * @v gma		General management agent
+ * @v mad		MAD response without DR fields filled in
+ * @ret mad		MAD response with DR fields filled in
+ */
+static union ib_mad * ib_sma_dr_response ( struct ib_gma *gma,
+					   union ib_mad *mad ) {
+	struct ib_mad_hdr *hdr = &mad->hdr;
+	struct ib_mad_smp *smp = &mad->smp;
+	unsigned int hop_pointer;
+	unsigned int hop_count;
+
+	/* Set response fields for directed route SMPs */
+	if ( hdr->mgmt_class == IB_MGMT_CLASS_SUBN_DIRECTED_ROUTE ) {
+		hdr->status |= htons ( IB_SMP_STATUS_D_INBOUND );
+		hop_pointer = smp->mad_hdr.class_specific.smp.hop_pointer;
+		hop_count = smp->mad_hdr.class_specific.smp.hop_count;
+		assert ( hop_count == hop_pointer );
+		if ( hop_pointer < ( sizeof ( smp->return_path.hops ) /
+				     sizeof ( smp->return_path.hops[0] ) ) ) {
+			smp->return_path.hops[hop_pointer] = gma->ibdev->port;
+		} else {
+			DBGC ( gma, "GMA %p invalid hop pointer %d\n",
+			       gma, hop_pointer );
+			return NULL;
+		}
+	}
+
+	return mad;
+}
+
 /**
  * Get node information
  *
  * @v gma		General management agent
  * @v mad		MAD
+ * @ret response	MAD response
  */
-static void ib_sma_get_node_info ( struct ib_gma *gma,
-				   union ib_mad *mad ) {
+static union ib_mad * ib_sma_get_node_info ( struct ib_gma *gma,
+					     union ib_mad *mad ) {
 	struct ib_device *ibdev = gma->ibdev;
 	struct ib_node_info *node_info = &mad->smp.smp_data.node_info;
 
 		 sizeof ( node_info->port_guid ) );
 	node_info->partition_cap = htons ( 1 );
 	node_info->local_port_num = ibdev->port;
+
+	mad->hdr.method = IB_MGMT_METHOD_GET_RESP;
+	return ib_sma_dr_response ( gma, mad );
 }
 
 /**
  *
  * @v gma		General management agent
  * @v mad		MAD
+ * @ret response	MAD response
  */
-static void ib_sma_get_node_desc ( struct ib_gma *gma,
-				   union ib_mad *mad ) {
+static union ib_mad * ib_sma_get_node_desc ( struct ib_gma *gma,
+					     union ib_mad *mad ) {
 	struct ib_device *ibdev = gma->ibdev;
 	struct ib_node_desc *node_desc = &mad->smp.smp_data.node_desc;
 	struct ib_gid_half *guid = &ibdev->gid.u.half[1];
 		   guid->bytes[0], guid->bytes[1], guid->bytes[2],
 		   guid->bytes[3], guid->bytes[4], guid->bytes[5],
 		   guid->bytes[6], guid->bytes[7], ibdev->dev->name );
+
+	mad->hdr.method = IB_MGMT_METHOD_GET_RESP;
+	return ib_sma_dr_response ( gma, mad );
 }
 
 /**
  *
  * @v gma		General management agent
  * @v mad		MAD
+ * @ret response	MAD response
  */
-static void ib_sma_get_guid_info ( struct ib_gma *gma,
-				   union ib_mad *mad ) {
+static union ib_mad * ib_sma_get_guid_info ( struct ib_gma *gma,
+					     union ib_mad *mad ) {
 	struct ib_device *ibdev = gma->ibdev;
 	struct ib_guid_info *guid_info = &mad->smp.smp_data.guid_info;
 
 	memset ( guid_info, 0, sizeof ( *guid_info ) );
 	memcpy ( guid_info->guid[0], &ibdev->gid.u.half[1],
 		 sizeof ( guid_info->guid[0] ) );
+
+	mad->hdr.method = IB_MGMT_METHOD_GET_RESP;
+	return ib_sma_dr_response ( gma, mad );
 }
 
 /**
  *
  * @v gma		General management agent
  * @v mad		MAD
+ * @ret response	MAD response
  */
-static void ib_sma_get_port_info ( struct ib_gma *gma,
-				   union ib_mad *mad ) {
+static union ib_mad * ib_sma_get_port_info ( struct ib_gma *gma,
+					     union ib_mad *mad ) {
 	struct ib_device *ibdev = gma->ibdev;
 	struct ib_port_info *port_info = &mad->smp.smp_data.port_info;
 
 	port_info->init_type_reply__mtu_cap = IB_MTU_2048;
 	port_info->operational_vls__enforcement = ( IB_VL_0 << 4 );
 	port_info->guid_cap = 1;
+
+	mad->hdr.method = IB_MGMT_METHOD_GET_RESP;
+	return ib_sma_dr_response ( gma, mad );
 }
 
 /**
  *
  * @v gma		General management agent
  * @v mad		MAD
+ * @ret response	MAD response
  */
-static void ib_sma_set_port_info ( struct ib_gma *gma,
-				   union ib_mad *mad ) {
+static union ib_mad * ib_sma_set_port_info ( struct ib_gma *gma,
+					     union ib_mad *mad ) {
 	struct ib_device *ibdev = gma->ibdev;
 	const struct ib_port_info *port_info = &mad->smp.smp_data.port_info;
 	int rc;
 			htons ( IB_MGMT_STATUS_UNSUPPORTED_METHOD_ATTR );
 	}
 
-	ib_sma_get_port_info ( gma, mad );
+	return ib_sma_get_port_info ( gma, mad );
 }
 
 /**
  *
  * @v gma		General management agent
  * @v mad		MAD
+ * @ret response	MAD response
  */
-static void ib_sma_get_pkey_table ( struct ib_gma *gma,
-				    union ib_mad *mad ) {
+static union ib_mad * ib_sma_get_pkey_table ( struct ib_gma *gma,
+					      union ib_mad *mad ) {
 	struct ib_device *ibdev = gma->ibdev;
 	struct ib_pkey_table *pkey_table = &mad->smp.smp_data.pkey_table;
 
+	mad->hdr.method = IB_MGMT_METHOD_GET_RESP;
 	memset ( pkey_table, 0, sizeof ( *pkey_table ) );
 	pkey_table->pkey[0] = htons ( ibdev->pkey );
+
+	mad->hdr.method = IB_MGMT_METHOD_GET_RESP;
+	return ib_sma_dr_response ( gma, mad );
 }
 
 /**
  *
  * @v gma		General management agent
  * @v mad		MAD
+ * @ret response	MAD response
  */
-static void ib_sma_set_pkey_table ( struct ib_gma *gma,
-				    union ib_mad *mad ) {
+static union ib_mad * ib_sma_set_pkey_table ( struct ib_gma *gma,
+					      union ib_mad *mad ) {
 	struct ib_device *ibdev = gma->ibdev;
 	struct ib_pkey_table *pkey_table = &mad->smp.smp_data.pkey_table;
 
 	ibdev->pkey = ntohs ( pkey_table->pkey[0] );
 
-	ib_sma_get_pkey_table ( gma, mad );
+	return ib_sma_get_pkey_table ( gma, mad );
 }
 
 /** List of attribute handlers */
 		.mgmt_class_ignore = IB_SMP_CLASS_IGNORE,
 		.class_version = IB_SMP_CLASS_VERSION,
 		.method = IB_MGMT_METHOD_GET,
-		.resp_method = IB_MGMT_METHOD_GET_RESP,
 		.attr_id = htons ( IB_SMP_ATTR_NODE_INFO ),
 		.handle = ib_sma_get_node_info,
 	},
 		.mgmt_class_ignore = IB_SMP_CLASS_IGNORE,
 		.class_version = IB_SMP_CLASS_VERSION,
 		.method = IB_MGMT_METHOD_GET,
-		.resp_method = IB_MGMT_METHOD_GET_RESP,
 		.attr_id = htons ( IB_SMP_ATTR_NODE_DESC ),
 		.handle = ib_sma_get_node_desc,
 	},
 		.mgmt_class_ignore = IB_SMP_CLASS_IGNORE,
 		.class_version = IB_SMP_CLASS_VERSION,
 		.method = IB_MGMT_METHOD_GET,
-		.resp_method = IB_MGMT_METHOD_GET_RESP,
 		.attr_id = htons ( IB_SMP_ATTR_GUID_INFO ),
 		.handle = ib_sma_get_guid_info,
 	},
 		.mgmt_class_ignore = IB_SMP_CLASS_IGNORE,
 		.class_version = IB_SMP_CLASS_VERSION,
 		.method = IB_MGMT_METHOD_GET,
-		.resp_method = IB_MGMT_METHOD_GET_RESP,
 		.attr_id = htons ( IB_SMP_ATTR_PORT_INFO ),
 		.handle = ib_sma_get_port_info,
 	},
 		.mgmt_class_ignore = IB_SMP_CLASS_IGNORE,
 		.class_version = IB_SMP_CLASS_VERSION,
 		.method = IB_MGMT_METHOD_SET,
-		.resp_method = IB_MGMT_METHOD_GET_RESP,
 		.attr_id = htons ( IB_SMP_ATTR_PORT_INFO ),
 		.handle = ib_sma_set_port_info,
 	},
 		.mgmt_class_ignore = IB_SMP_CLASS_IGNORE,
 		.class_version = IB_SMP_CLASS_VERSION,
 		.method = IB_MGMT_METHOD_GET,
-		.resp_method = IB_MGMT_METHOD_GET_RESP,
 		.attr_id = htons ( IB_SMP_ATTR_PKEY_TABLE ),
 		.handle = ib_sma_get_pkey_table,
 	},
 		.mgmt_class_ignore = IB_SMP_CLASS_IGNORE,
 		.class_version = IB_SMP_CLASS_VERSION,
 		.method = IB_MGMT_METHOD_SET,
-		.resp_method = IB_MGMT_METHOD_GET_RESP,
 		.attr_id = htons ( IB_SMP_ATTR_PKEY_TABLE ),
 		.handle = ib_sma_set_pkey_table,
 	},
  *
  * @v gma		General management agent
  * @v mad		MAD
+ * @ret mad		MAD response
  */
-static void ib_handle_mad ( struct ib_gma *gma, union ib_mad *mad ) {
+static union ib_mad * ib_handle_mad ( struct ib_gma *gma, union ib_mad *mad ) {
 	struct ib_mad_hdr *hdr = &mad->hdr;
 	struct ib_gma_handler *handler;
 
 		     ( handler->class_version == hdr->class_version ) &&
 		     ( handler->method == hdr->method ) &&
 		     ( handler->attr_id == hdr->attr_id ) ) {
-			hdr->method = handler->resp_method;
-			handler->handle ( gma, mad );
-			return;
+			return handler->handle ( gma, mad );
 		}
 	}
 
 	hdr->method = IB_MGMT_METHOD_TRAP;
 	hdr->status = htons ( IB_MGMT_STATUS_UNSUPPORTED_METHOD_ATTR );
+	return mad;
 }
 
 /**
 	struct ib_mad_request *request;
 	union ib_mad *mad;
 	struct ib_mad_hdr *hdr;
-	unsigned int hop_pointer;
-	unsigned int hop_count;
+	union ib_mad *response;
 
 	/* Ignore errors */
 	if ( rc != 0 ) {
 	}
 
 	/* Handle MAD */
-	ib_handle_mad ( gma, mad );
-
-	/* Finish processing if we have no response to send */
-	if ( ! hdr->method )
+	if ( ( response = ib_handle_mad ( gma, mad ) ) == NULL )
 		goto out;
 
+	/* Re-use I/O buffer for response */
+	memcpy ( mad, response, sizeof ( *mad ) );
 	DBGC ( gma, "GMA %p TX TID %08x%08x (%02x,%02x,%02x,%04x) status "
 	       "%04x\n", gma, ntohl ( hdr->tid[0] ), ntohl ( hdr->tid[1] ),
 	       hdr->mgmt_class, hdr->class_version, hdr->method,
 	       ntohs ( hdr->attr_id ), ntohs ( hdr->status ) );
 	DBGC2_HDA ( gma, 0, mad, sizeof ( *mad ) );
 
-	/* Set response fields for directed route SMPs */
-	if ( hdr->mgmt_class == IB_MGMT_CLASS_SUBN_DIRECTED_ROUTE ) {
-		struct ib_mad_smp *smp = &mad->smp;
-
-		hdr->status |= htons ( IB_SMP_STATUS_D_INBOUND );
-		hop_pointer = smp->mad_hdr.class_specific.smp.hop_pointer;
-		hop_count = smp->mad_hdr.class_specific.smp.hop_count;
-		assert ( hop_count == hop_pointer );
-		if ( hop_pointer < ( sizeof ( smp->return_path.hops ) /
-				     sizeof ( smp->return_path.hops[0] ) ) ) {
-			smp->return_path.hops[hop_pointer] = ibdev->port;
-		} else {
-			DBGC ( gma, "GMA %p invalid hop pointer %d\n",
-			       gma, hop_pointer );
-			goto out;
-		}
-	}
-
 	/* Send MAD response, if applicable */
 	if ( ( rc = ib_post_send ( ibdev, qp, av,
 				   iob_disown ( iobuf ) ) ) != 0 ) {

src/net/infiniband/ib_mcast.c

  *
  * @v gma		General management agent
  * @v mad		MAD
+ * @ret mad		MAD response
  */
-static void ib_handle_mc_member_join ( struct ib_gma *gma,
-				       union ib_mad *mad ) {
+static union ib_mad * ib_handle_mc_member_join ( struct ib_gma *gma,
+						 union ib_mad *mad ) {
 	struct ib_device *ibdev = gma->ibdev;
 	struct ib_mc_member_record *mc_member_record =
 		&mad->sa.sa_data.mc_member_record;
 	if ( mad->hdr.status != htons ( IB_MGMT_STATUS_OK ) ) {
 		DBGC ( gma, "GMA %p join failed with status %04x\n",
 		       gma, ntohs ( mad->hdr.status ) );
-		return;
+		return NULL;
 	}
 
 	/* Extract MAD parameters */
 		       ntohl ( gid->u.dwords[1] ),
 		       ntohl ( gid->u.dwords[2] ),
 		       ntohl ( gid->u.dwords[3] ) );
-		return;
+		return NULL;
 	}
 	DBGC ( gma, "GMA %p QPN %lx joined %08x:%08x:%08x:%08x qkey %lx\n",
 	       gma, qp->qpn, ntohl ( gid->u.dwords[0] ),
 	if ( ( rc = ib_modify_qp ( ibdev, qp, IB_MODIFY_QKEY, qkey ) ) != 0 ) {
 		DBGC ( gma, "GMA %p QPN %lx could not modify qkey: %s\n",
 		       gma, qp->qpn, strerror ( rc ) );
-		return;
+		return NULL;
 	}
+
+	return NULL;
 }
 
 /**
  *
  * @v gma		General management agent
  * @v mad		MAD
+ * @v response		MAD response
  */
-static void ib_handle_mc_member_leave ( struct ib_gma *gma,
-					union ib_mad *mad ) {
+static union ib_mad * ib_handle_mc_member_leave ( struct ib_gma *gma,
+						  union ib_mad *mad ) {
 	struct ib_mc_member_record *mc_member_record =
 		&mad->sa.sa_data.mc_member_record;
 	struct ib_gid *gid;
 	if ( mad->hdr.status != htons ( IB_MGMT_STATUS_OK ) ) {
 		DBGC ( gma, "GMA %p leave failed with status %04x\n",
 		       gma, ntohs ( mad->hdr.status ) );
-		return;
+		return NULL;
 	}
 
 	/* Extract MAD parameters */
 	DBGC ( gma, "GMA %p left %08x:%08x:%08x:%08x\n", gma,
 	       ntohl ( gid->u.dwords[0] ), ntohl ( gid->u.dwords[1] ),
 	       ntohl ( gid->u.dwords[2] ), ntohl ( gid->u.dwords[3] ) );
+
+	return NULL;
 }
 
 /** Multicast membership record response handler */

src/net/infiniband/ib_pathrec.c

  *
  * @v gma		General management agent
  * @v mad		MAD
+ * @ret response	MAD response
  */
-static void ib_handle_path_record ( struct ib_gma *gma,
-				    union ib_mad *mad ) {
+static union ib_mad * ib_handle_path_record ( struct ib_gma *gma,
+					      union ib_mad *mad ) {
 	struct ib_device *ibdev = gma->ibdev;
 	struct ib_path_record *path_record = &mad->sa.sa_data.path_record;
 	struct ib_gid *dgid = &path_record->dgid;
 	if ( mad->hdr.status != htons ( IB_MGMT_STATUS_OK ) ) {
 		DBGC ( gma, "GMA %p path record lookup failed with status "
 		       "%04x\n", gma, ntohs ( mad->hdr.status ) );
-		return;
+		return NULL;
 	}
 
 	/* Extract values from MAD */
 		cached->rate = rate;
 		cached->sl = sl;
 	}
+
+	return NULL;
 }
 
 /** Path record response handler */