net/sched: taprio: centralize mqprio qopt validation

There is a lot of code in taprio which is "borrowed" from mqprio.
It makes sense to put a stop to the "borrowing" and start actually
reusing code.

Because taprio and mqprio are built as part of different kernel modules,
code reuse can only take place either by writing it as static inline
(limiting), putting it in sch_generic.o (not generic enough), or
creating a third auto-selectable kernel module which only holds library
code. I opted for the third variant.

In a previous change, mqprio gained support for reverse TC:TXQ mappings,
something which taprio still denies. Make taprio use the same validation
logic so that it supports this configuration as well.

The taprio code didn't enforce TXQ overlaps in txtime-assist mode and
that looks intentional, even if I've no idea why that might be. Preserve
that, but add a comment.

There isn't any dedicated MAINTAINERS entry for mqprio, so nothing to
update there.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Reviewed-by: Gerhard Engleder <gerhard@engleder-embedded.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 16 insertions, 0 deletions

diff --git a/net/sched/sch_mqprio_lib.h b/net/sched/sch_mqprio_lib.h
new file mode 100644
index 000000000000..353787a25648
--- /dev/null
+++ b/net/sched/sch_mqprio_lib.h
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __SCH_MQPRIO_LIB_H
+#define __SCH_MQPRIO_LIB_H
+
+#include <linux/types.h>
+
+struct net_device;
+struct netlink_ext_ack;
+struct tc_mqprio_qopt;
+
+int mqprio_validate_qopt(struct net_device *dev, struct tc_mqprio_qopt *qopt,
+			 bool validate_queue_counts,
+			 bool allow_overlapping_txqs,
+			 struct netlink_ext_ack *extack);
+
+#endif