Change igc_ethtool_set_rxfh() to accept and save a userspace-provided
RSS key. When a key is provided, store it in the adapter and write the
RSSRK registers accordingly.

This can be tested using `ethtool -X <dev> hkey <key>`.

Signed-off-by: Kohei Enju <kohei@enjuk.jp>
---
 drivers/net/ethernet/intel/igc/igc_ethtool.c | 30 +++++++++++---------
 1 file changed, 17 insertions(+), 13 deletions(-)

diff --git a/drivers/net/ethernet/intel/igc/igc_ethtool.c b/drivers/net/ethernet/intel/igc/igc_ethtool.c
index 661b044073ca..eb5b146f6f10 100644
--- a/drivers/net/ethernet/intel/igc/igc_ethtool.c
+++ b/drivers/net/ethernet/intel/igc/igc_ethtool.c
@@ -1539,24 +1539,28 @@ static int igc_ethtool_set_rxfh(struct net_device *netdev,
 	int i;
 
 	/* We do not allow change in unsupported parameters */
-	if (rxfh->key ||
-	    (rxfh->hfunc != ETH_RSS_HASH_NO_CHANGE &&
-	     rxfh->hfunc != ETH_RSS_HASH_TOP))
+	if (rxfh->hfunc != ETH_RSS_HASH_NO_CHANGE &&
+	    rxfh->hfunc != ETH_RSS_HASH_TOP)
 		return -EOPNOTSUPP;
-	if (!rxfh->indir)
-		return 0;
 
-	num_queues = adapter->rss_queues;
+	if (rxfh->indir) {
+		num_queues = adapter->rss_queues;
 
-	/* Verify user input. */
-	for (i = 0; i < IGC_RETA_SIZE; i++)
-		if (rxfh->indir[i] >= num_queues)
-			return -EINVAL;
+		/* Verify user input. */
+		for (i = 0; i < IGC_RETA_SIZE; i++)
+			if (rxfh->indir[i] >= num_queues)
+				return -EINVAL;
 
-	for (i = 0; i < IGC_RETA_SIZE; i++)
-		adapter->rss_indir_tbl[i] = rxfh->indir[i];
+		for (i = 0; i < IGC_RETA_SIZE; i++)
+			adapter->rss_indir_tbl[i] = rxfh->indir[i];
 
-	igc_write_rss_indir_tbl(adapter);
+		igc_write_rss_indir_tbl(adapter);
+	}
+
+	if (rxfh->key) {
+		memcpy(adapter->rss_key, rxfh->key, sizeof(adapter->rss_key));
+		igc_write_rss_key(adapter);
+	}
 
 	return 0;
 }
-- 
2.51.0