On Mon, Feb 06, 2023 at 17:02, Simon Horman [off-list ref] wrote:

Just to clarify my suggestion one last time, it would be along the lines
of the following (completely untested!). I feel that it robustly covers
all cases for fdb_flags. And as a bonus doesn't need to be modified
if other (unsupported) flags are added in future.

	if (fdb_flags & ~(DSA_FDB_FLAG_DYNAMIC))
		return -EOPNOTSUPP;

	is_dynamic = !!(fdb_flags & DSA_FDB_FLAG_DYNAMIC)
	if (is_dynamic)
		state = MV88E6XXX_G1_ATU_DATA_STATE_UC_AGE_7_NEWEST;


And perhaps for other drivers:

	if (fdb_flags & ~(DSA_FDB_FLAG_DYNAMIC))
		return -EOPNOTSUPP;
	if (fdb_flags)
		return 0;

Perhaps a helper would be warranted for the above.

How would such a helper look? Inline function is not clean.

But in writing this I think that, perhaps drivers could return -EOPNOTSUPP
for the DSA_FDB_FLAG_DYNAMIC case and the caller can handle, rather tha
propagate, -EOPNOTSUPP.

I looked at that, but changing the caller is also a bit ugly.

Returning -EOPNOTSUPP is the normal way to drivers to respond to requests
for unsupported hardware offloads. Sticking to that may be clearner
in the long run. That said, I do agree your current patch is correct
given the flag that is defined (by your patchset).