[PATCH v4 3/6] can: c_can: add a comment about IF_RX interface's use

After reading the commit 640916db2bf7 ("can: c_can: Make it SMP safe")
it may sound strange to see the IF_RX interface used by the
can_inval_tx_object function. A comment was added to avoid any
misunderstanding.

Signed-off-by: Dario Binacchi <redacted>

---

Changes in v4:
- Restore IF_RX interface.
- Add a comment to clarify why IF_RX interface is used instead of IF_TX.

 drivers/net/can/c_can/c_can.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/can/c_can/c_can.c b/drivers/net/can/c_can/c_can.c
index dbcc1c1c92d6..6c6d0d0ff7b8 100644
--- a/drivers/net/can/c_can/c_can.c
+++ b/drivers/net/can/c_can/c_can.c

@@ -732,6 +732,12 @@ static void c_can_do_tx(struct net_device *dev)
 		idx--;
 		pend &= ~(1 << idx);
 		obj = idx + C_CAN_MSG_OBJ_TX_FIRST;
+
+		/*
+		 * We use IF_RX interface instead of IF_TX because we are
+		 * called from c_can_poll(), which runs inside NAPI. We are
+		 * not trasmitting.
+		 */
 		c_can_inval_tx_object(dev, IF_RX, obj);
 		can_get_echo_skb(dev, idx, NULL);
 		bytes += priv->dlc[idx];

-- 
2.17.1