gve: DQO: avoid unused variable warnings

The use of dma_unmap_addr()/dma_unmap_len() in the driver causes
multiple warnings when these macros are defined as empty, e.g.
in an ARCH=i386 allmodconfig build:

drivers/net/ethernet/google/gve/gve_tx_dqo.c: In function 'gve_tx_add_skb_no_copy_dqo':
drivers/net/ethernet/google/gve/gve_tx_dqo.c:494:40: error: unused variable 'buf' [-Werror=unused-variable]
  494 |                 struct gve_tx_dma_buf *buf =

This is not how the NEED_DMA_MAP_STATE macros are meant to work,
as they rely on never using local variables or a temporary structure
like gve_tx_dma_buf.

Remote the gve_tx_dma_buf definition and open-code the contents
in all places to avoid the warning. This causes some rather long
lines but otherwise ends up making the driver slightly smaller.

Fixes: a57e5de4 ("gve: DQO: Add TX path")
Link: https://lore.kernel.org/netdev/20210723231957.1113800-1-bcf@google.com/
Link: https://lore.kernel.org/netdev/20210721151100.2042139-1-arnd@kernel.org/Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/google/gve/gve.h

@@ -224,11 +224,6 @@ struct gve_tx_iovec {
 	u32 iov_padding; /* padding associated with this segment */
 };
 
-struct gve_tx_dma_buf {
-	DEFINE_DMA_UNMAP_ADDR(dma);
-	DEFINE_DMA_UNMAP_LEN(len);
-};
-
 /* Tracks the memory in the fifo occupied by the skb. Mapped 1:1 to a desc
  * ring entry but only used for a pkt_desc not a seg_desc
  */
@@ -236,7 +231,10 @@ struct gve_tx_buffer_state {
 	struct sk_buff *skb; /* skb for this pkt */
 	union {
 		struct gve_tx_iovec iov[GVE_TX_MAX_IOVEC]; /* segments of this pkt */
-		struct gve_tx_dma_buf buf;
+		struct {
+			DEFINE_DMA_UNMAP_ADDR(dma);
+			DEFINE_DMA_UNMAP_LEN(len);
+		};
 	};
 };
 
@@ -280,7 +278,8 @@ struct gve_tx_pending_packet_dqo {
 	 * All others correspond to `skb`'s frags and should be unmapped with
 	 * `dma_unmap_page`.
 	 */
-	struct gve_tx_dma_buf bufs[MAX_SKB_FRAGS + 1];
+	DEFINE_DMA_UNMAP_ADDR(dma[MAX_SKB_FRAGS + 1]);
+	DEFINE_DMA_UNMAP_LEN(len[MAX_SKB_FRAGS + 1]);
 	u16 num_bufs;
 
 	/* Linked list index to next element in the list, or -1 if none */

drivers/net/ethernet/google/gve/gve_tx.c

@@ -303,15 +303,15 @@ static inline int gve_skb_fifo_bytes_required(struct gve_tx_ring *tx,
 static void gve_tx_unmap_buf(struct device *dev, struct gve_tx_buffer_state *info)
 {
 	if (info->skb) {
-		dma_unmap_single(dev, dma_unmap_addr(&info->buf, dma),
-				 dma_unmap_len(&info->buf, len),
+		dma_unmap_single(dev, dma_unmap_addr(info, dma),
+				 dma_unmap_len(info, len),
 				 DMA_TO_DEVICE);
-		dma_unmap_len_set(&info->buf, len, 0);
+		dma_unmap_len_set(info, len, 0);
 	} else {
-		dma_unmap_page(dev, dma_unmap_addr(&info->buf, dma),
-			       dma_unmap_len(&info->buf, len),
+		dma_unmap_page(dev, dma_unmap_addr(info, dma),
+			       dma_unmap_len(info, len),
 			       DMA_TO_DEVICE);
-		dma_unmap_len_set(&info->buf, len, 0);
+		dma_unmap_len_set(info, len, 0);
 	}
 }
 
@@ -491,7 +491,6 @@ static int gve_tx_add_skb_no_copy(struct gve_priv *priv, struct gve_tx_ring *tx,
 	struct gve_tx_buffer_state *info;
 	bool is_gso = skb_is_gso(skb);
 	u32 idx = tx->req & tx->mask;
-	struct gve_tx_dma_buf *buf;
 	u64 addr;
 	u32 len;
 	int i;
@@ -515,9 +514,8 @@ static int gve_tx_add_skb_no_copy(struct gve_priv *priv, struct gve_tx_ring *tx,
 		tx->dma_mapping_error++;
 		goto drop;
 	}
-	buf = &info->buf;
-	dma_unmap_len_set(buf, len, len);
-	dma_unmap_addr_set(buf, dma, addr);
+	dma_unmap_len_set(info, len, len);
+	dma_unmap_addr_set(info, dma, addr);
 
 	payload_nfrags = shinfo->nr_frags;
 	if (hlen < len) {
@@ -549,10 +547,9 @@ static int gve_tx_add_skb_no_copy(struct gve_priv *priv, struct gve_tx_ring *tx,
 			tx->dma_mapping_error++;
 			goto unmap_drop;
 		}
-		buf = &tx->info[idx].buf;
 		tx->info[idx].skb = NULL;
-		dma_unmap_len_set(buf, len, len);
-		dma_unmap_addr_set(buf, dma, addr);
+		dma_unmap_len_set(&tx->info[idx], len, len);
+		dma_unmap_addr_set(&tx->info[idx], dma, addr);
 
 		gve_tx_fill_seg_desc(seg_desc, skb, is_gso, len, addr);
 	}

drivers/net/ethernet/google/gve/gve_tx_dqo.c

@@ -85,18 +85,16 @@ static void gve_tx_clean_pending_packets(struct gve_tx_ring *tx)
 		int j;
 
 		for (j = 0; j < cur_state->num_bufs; j++) {
-			struct gve_tx_dma_buf *buf = &cur_state->bufs[j];
-
 			if (j == 0) {
 				dma_unmap_single(tx->dev,
-						 dma_unmap_addr(buf, dma),
-						 dma_unmap_len(buf, len),
-						 DMA_TO_DEVICE);
+					dma_unmap_addr(cur_state, dma[j]),
+					dma_unmap_len(cur_state, len[j]),
+					DMA_TO_DEVICE);
 			} else {
 				dma_unmap_page(tx->dev,
-					       dma_unmap_addr(buf, dma),
-					       dma_unmap_len(buf, len),
-					       DMA_TO_DEVICE);
+					dma_unmap_addr(cur_state, dma[j]),
+					dma_unmap_len(cur_state, len[j]),
+					DMA_TO_DEVICE);
 			}
 		}
 		if (cur_state->skb) {
@@ -457,15 +455,15 @@ static int gve_tx_add_skb_no_copy_dqo(struct gve_tx_ring *tx,
 	const bool is_gso = skb_is_gso(skb);
 	u32 desc_idx = tx->dqo_tx.tail;
 
-	struct gve_tx_pending_packet_dqo *pending_packet;
+	struct gve_tx_pending_packet_dqo *pkt;
 	struct gve_tx_metadata_dqo metadata;
 	s16 completion_tag;
 	int i;
 
-	pending_packet = gve_alloc_pending_packet(tx);
-	pending_packet->skb = skb;
-	pending_packet->num_bufs = 0;
-	completion_tag = pending_packet - tx->dqo.pending_packets;
+	pkt = gve_alloc_pending_packet(tx);
+	pkt->skb = skb;
+	pkt->num_bufs = 0;
+	completion_tag = pkt - tx->dqo.pending_packets;
 
 	gve_extract_tx_metadata_dqo(skb, &metadata);
 	if (is_gso) {
@@ -493,8 +491,6 @@ static int gve_tx_add_skb_no_copy_dqo(struct gve_tx_ring *tx,
 
 	/* Map the linear portion of skb */
 	{
-		struct gve_tx_dma_buf *buf =
-			&pending_packet->bufs[pending_packet->num_bufs];
 		u32 len = skb_headlen(skb);
 		dma_addr_t addr;
 
@@ -502,9 +498,9 @@ static int gve_tx_add_skb_no_copy_dqo(struct gve_tx_ring *tx,
 		if (unlikely(dma_mapping_error(tx->dev, addr)))
 			goto err;
 
-		dma_unmap_len_set(buf, len, len);
-		dma_unmap_addr_set(buf, dma, addr);
-		++pending_packet->num_bufs;
+		dma_unmap_len_set(pkt, len[pkt->num_bufs], len);
+		dma_unmap_addr_set(pkt, dma[pkt->num_bufs], addr);
+		++pkt->num_bufs;
 
 		gve_tx_fill_pkt_desc_dqo(tx, &desc_idx, skb, len, addr,
 					 completion_tag,
@@ -512,8 +508,6 @@ static int gve_tx_add_skb_no_copy_dqo(struct gve_tx_ring *tx,
 	}
 
 	for (i = 0; i < shinfo->nr_frags; i++) {
-		struct gve_tx_dma_buf *buf =
-			&pending_packet->bufs[pending_packet->num_bufs];
 		const skb_frag_t *frag = &shinfo->frags[i];
 		bool is_eop = i == (shinfo->nr_frags - 1);
 		u32 len = skb_frag_size(frag);
@@ -523,9 +517,9 @@ static int gve_tx_add_skb_no_copy_dqo(struct gve_tx_ring *tx,
 		if (unlikely(dma_mapping_error(tx->dev, addr)))
 			goto err;
 
-		dma_unmap_len_set(buf, len, len);
-		dma_unmap_addr_set(buf, dma, addr);
-		++pending_packet->num_bufs;
+		dma_unmap_len_set(pkt, len[pkt->num_bufs], len);
+		dma_unmap_addr_set(pkt, dma[pkt->num_bufs], addr);
+		++pkt->num_bufs;
 
 		gve_tx_fill_pkt_desc_dqo(tx, &desc_idx, skb, len, addr,
 					 completion_tag, is_eop, is_gso);
@@ -552,22 +546,23 @@ static int gve_tx_add_skb_no_copy_dqo(struct gve_tx_ring *tx,
 	return 0;
 
 err:
-	for (i = 0; i < pending_packet->num_bufs; i++) {
-		struct gve_tx_dma_buf *buf = &pending_packet->bufs[i];
-
+	for (i = 0; i < pkt->num_bufs; i++) {
 		if (i == 0) {
-			dma_unmap_single(tx->dev, dma_unmap_addr(buf, dma),
-					 dma_unmap_len(buf, len),
+			dma_unmap_single(tx->dev,
+					 dma_unmap_addr(pkt, dma[i]),
+					 dma_unmap_len(pkt, len[i]),
 					 DMA_TO_DEVICE);
 		} else {
-			dma_unmap_page(tx->dev, dma_unmap_addr(buf, dma),
-				       dma_unmap_len(buf, len), DMA_TO_DEVICE);
+			dma_unmap_page(tx->dev,
+				       dma_unmap_addr(pkt, dma[i]),
+				       dma_unmap_len(pkt, len[i]),
+				       DMA_TO_DEVICE);
 		}
 	}
 
-	pending_packet->skb = NULL;
-	pending_packet->num_bufs = 0;
-	gve_free_pending_packet(tx, pending_packet);
+	pkt->skb = NULL;
+	pkt->num_bufs = 0;
+	gve_free_pending_packet(tx, pkt);
 
 	return -1;
 }
@@ -725,12 +720,12 @@ static void add_to_list(struct gve_tx_ring *tx, struct gve_index_list *list,
 
 static void remove_from_list(struct gve_tx_ring *tx,
 			     struct gve_index_list *list,
-			     struct gve_tx_pending_packet_dqo *pending_packet)
+			     struct gve_tx_pending_packet_dqo *pkt)
 {
 	s16 prev_index, next_index;
 
-	prev_index = pending_packet->prev;
-	next_index = pending_packet->next;
+	prev_index = pkt->prev;
+	next_index = pkt->next;
 
 	if (prev_index == -1) {
 		/* Node is head */
@@ -747,21 +742,18 @@ static void remove_from_list(struct gve_tx_ring *tx,
 }
 
 static void gve_unmap_packet(struct device *dev,
-			     struct gve_tx_pending_packet_dqo *pending_packet)
+			     struct gve_tx_pending_packet_dqo *pkt)
 {
-	struct gve_tx_dma_buf *buf;
 	int i;
 
 	/* SKB linear portion is guaranteed to be mapped */
-	buf = &pending_packet->bufs[0];
-	dma_unmap_single(dev, dma_unmap_addr(buf, dma),
-			 dma_unmap_len(buf, len), DMA_TO_DEVICE);
-	for (i = 1; i < pending_packet->num_bufs; i++) {
-		buf = &pending_packet->bufs[i];
-		dma_unmap_page(dev, dma_unmap_addr(buf, dma),
-			       dma_unmap_len(buf, len), DMA_TO_DEVICE);
+	dma_unmap_single(dev, dma_unmap_addr(pkt, dma[0]),
+			 dma_unmap_len(pkt, len[0]), DMA_TO_DEVICE);
+	for (i = 1; i < pkt->num_bufs; i++) {
+		dma_unmap_page(dev, dma_unmap_addr(pkt, dma[i]),
+			       dma_unmap_len(pkt, len[i]), DMA_TO_DEVICE);
 	}
-	pending_packet->num_bufs = 0;
+	pkt->num_bufs = 0;
 }
 
 /* Completion types and expected behavior: