Currently, netdevsim supports TC offloads only for filter blocks and the
'taprio' qdisc. This improves coverage for situations where

  .ndo_setup_tc(dev, TC_SETUP_QDISC_TAPRIO, ...)

returns 0, but the code can be generalized for offloading most of the
Linux qdiscs we have at the moment. Generalize netdevsim qdisc offload,
by providing:
 - a function that returns 0 on 'setup'/'destroy'/'get_stats' commands
   read from qdisc-specific offload parameters, and returns -EOPNOTSUPP
   otherwise, namely "handle_<qdisc_name>()"
 - a case label handling TC_SETUP_QDISC_<qdisc_name> in nsim_setup_tc().

This commit has no functional change.

Signed-off-by: Davide Caratti <dcaratti@redhat.com>
---
 drivers/net/netdevsim/tc.c | 57 ++++++++++++++++++++++----------------
 1 file changed, 33 insertions(+), 24 deletions(-)

diff --git a/drivers/net/netdevsim/tc.c b/drivers/net/netdevsim/tc.c
index 8a1960f5f99e..358fa5bb835f 100644
--- a/drivers/net/netdevsim/tc.c
+++ b/drivers/net/netdevsim/tc.c
@@ -11,32 +11,31 @@ nsim_setup_tc_block_cb(enum tc_setup_type type, void *type_data, void *cb_priv)
 	return nsim_bpf_setup_tc_block_cb(type, type_data, cb_priv);
 }
 
-static void nsim_taprio_stats(struct tc_taprio_qopt_stats *stats)
-{
-	stats->window_drops = 0;
-	stats->tx_overruns = 0;
-}
+static LIST_HEAD(nsim_block_cb_list);
 
-static int nsim_setup_tc_taprio(struct net_device *dev,
-				struct tc_taprio_qopt_offload *offload)
-{
-	int err = 0;
-
-	switch (offload->cmd) {
-	case TAPRIO_CMD_REPLACE:
-	case TAPRIO_CMD_DESTROY:
-		break;
-	case TAPRIO_CMD_STATS:
-		nsim_taprio_stats(&offload->stats);
-		break;
-	default:
-		err = -EOPNOTSUPP;
-	}
+#define QDISC_OFFLOAD_HANDLERS(X)					\
+	X(taprio, tc_taprio_qopt_offload, cmd, TAPRIO_CMD_REPLACE,	\
+	  TAPRIO_CMD_DESTROY, TAPRIO_CMD_STATS, stats)			\
 
-	return err;
+#define QH(NAME, OL_TYPE, CMD_FLD, O_REPLACE, O_DESTROY, O_STATS, STATS_FLD) \
+static int handle_##NAME(struct net_device *dev, struct OL_TYPE *offload) \
+{									\
+	switch (offload->CMD_FLD) {					\
+	case O_REPLACE:							\
+	case O_DESTROY:							\
+		/* Do nothing, accept offload */			\
+		return 0;						\
+	case O_STATS:							\
+		/* Zero out the requested stats block */		\
+		memset(&offload->STATS_FLD, 0, sizeof(offload->STATS_FLD)); \
+		return 0;						\
+	default:							\
+		return -EOPNOTSUPP;					\
+	}								\
 }
 
-static LIST_HEAD(nsim_block_cb_list);
+QDISC_OFFLOAD_HANDLERS(QH)
+#undef QH
 
 int
 nsim_setup_tc(struct net_device *dev, enum tc_setup_type type, void *type_data)
@@ -44,8 +43,18 @@ nsim_setup_tc(struct net_device *dev, enum tc_setup_type type, void *type_data)
 	struct netdevsim *ns = netdev_priv(dev);
 
 	switch (type) {
-	case TC_SETUP_QDISC_TAPRIO:
-		return nsim_setup_tc_taprio(dev, type_data);
+#define TC_QDISC_SETUP_CASES(X)						\
+	X(TC_SETUP_QDISC_TAPRIO, tc_taprio_qopt_offload, taprio)	\
+
+#define SC(SETUP_LABEL, OL_TYPE, NAME)					\
+	case SETUP_LABEL:						\
+	{								\
+		return handle_##NAME(dev, (struct OL_TYPE *)type_data); \
+	}
+
+	TC_QDISC_SETUP_CASES(SC)
+#undef SC
+
 	case TC_SETUP_BLOCK:
 		return flow_block_cb_setup_simple(type_data,
 						  &nsim_block_cb_list,
-- 
2.52.0