sfc: Document conditions for multicast replication vs filter replacement
Add the efx_filter_is_mc_recip() function to decide whether a filter
is for a multicast recipient and can coexist with other filters with
the same match values. Update efx_filter_insert_filter() kernel-doc
to explain the conditions for this.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
diff --git a/drivers/net/ethernet/sfc/efx.h b/drivers/net/ethernet/sfc/efx.h
index 3bbc047..9de28f6 100644
--- a/drivers/net/ethernet/sfc/efx.h
+++ b/drivers/net/ethernet/sfc/efx.h
@@ -79,13 +79,20 @@
* On success, return the filter ID.
* On failure, return a negative error code.
*
- * If an existing filter has equal match values to the new filter
- * spec, then the new filter might replace it, depending on the
- * relative priorities. If the existing filter has lower priority, or
- * if @replace_equal is set and it has equal priority, then it is
- * replaced. Otherwise the function fails, returning -%EPERM if
- * the existing filter has higher priority or -%EEXIST if it has
- * equal priority.
+ * If existing filters have equal match values to the new filter spec,
+ * then the new filter might replace them or the function might fail,
+ * as follows.
+ *
+ * 1. If the existing filters have lower priority, or @replace_equal
+ * is set and they have equal priority, replace them.
+ *
+ * 2. If the existing filters have higher priority, return -%EPERM.
+ *
+ * 3. If !efx_filter_is_mc_recipient(@spec), or the NIC does not
+ * support delivery to multiple recipients, return -%EEXIST.
+ *
+ * This implies that filters for multiple multicast recipients must
+ * all be inserted with the same priority and @replace_equal = %false.
*/
static inline s32 efx_filter_insert_filter(struct efx_nic *efx,
struct efx_filter_spec *spec,
@@ -169,6 +176,7 @@
static inline void efx_filter_rfs_expire(struct efx_channel *channel) {}
#define efx_filter_rfs_enabled() 0
#endif
+extern bool efx_filter_is_mc_recipient(const struct efx_filter_spec *spec);
/* Channels */
extern int efx_channel_dummy_op_int(struct efx_channel *channel);