mt76: allow drivers to drop rx packets early

This can be used to free received events without allocating an extra skb
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/dma.c

@@ -572,9 +572,7 @@ mt76_dma_rx_process(struct mt76_dev *dev, struct mt76_queue *q, int budget)
 		if (data_len < len + q->buf_offset) {
 			dev_kfree_skb(q->rx_head);
 			q->rx_head = NULL;
-
-			skb_free_frag(data);
-			continue;
+			goto free_frag;
 		}
 
 		if (q->rx_head) {
@@ -582,11 +580,14 @@ mt76_dma_rx_process(struct mt76_dev *dev, struct mt76_queue *q, int budget)
 			continue;
 		}
 
+		if (!more && dev->drv->rx_check &&
+		    !(dev->drv->rx_check(dev, data, len)))
+			goto free_frag;
+
 		skb = build_skb(data, q->buf_size);
-		if (!skb) {
-			skb_free_frag(data);
-			continue;
-		}
+		if (!skb)
+			goto free_frag;
+
 		skb_reserve(skb, q->buf_offset);
 
 		if (q == &dev->q_rx[MT_RXQ_MCU]) {
@@ -603,6 +604,10 @@ mt76_dma_rx_process(struct mt76_dev *dev, struct mt76_queue *q, int budget)
 		}
 
 		dev->drv->rx_skb(dev, q - dev->q_rx, skb);
+		continue;
+
+free_frag:
+		skb_free_frag(data);
 	}
 
 	mt76_dma_rx_fill(dev, q);

drivers/net/wireless/mediatek/mt76/mt76.h

@@ -373,6 +373,8 @@ struct mt76_driver_ops {
 
 	bool (*tx_status_data)(struct mt76_dev *dev, u8 *update);
 
+	bool (*rx_check)(struct mt76_dev *dev, void *data, int len);
+
 	void (*rx_skb)(struct mt76_dev *dev, enum mt76_rxq_id q,
 		       struct sk_buff *skb);