[PATCH v2] brcmfmac: fwsignal: Use struct_size() to simplify brcmf_fws_rxreorder()

[Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>]

In the "struct brcmf_ampdu_rx_reorder", change the 'pktslots' field into
flexible array.

It saves the size of a pointer when the memory is allocated and avoids
an indirection when the array is used.
It also removes the usage of a pointer arithmetic and saves a few lines of
code.

Finally, struct_size() can be used. It is not a must have here, because
it is easy to see that buf_size can not overflow, but still, it is a good
practice.

Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
Acked-by: Arend van Spriel <arend.vanspriel@xxxxxxxxxxxx>
---
Compile tested only

Changes in v2:
  - fix description of the 'pktslots' field   [Arend van Spriel]
  - add A-b tag

v1: https://lore.kernel.org/all/bd3ad239c4d1c49b94c1ba93e48c09df98ef86cb.1720951805.git.christophe.jaillet@xxxxxxxxxx/
---
 drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.h   | 4 ++--
 .../net/wireless/broadcom/brcm80211/brcmfmac/fwsignal.c   | 8 ++------
 2 files changed, 4 insertions(+), 8 deletions(-)

diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.h b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.h
index ea76b8d33401..39226b9c0fa8 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.h
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.h
@@ -48,20 +48,20 @@
 /**
  * struct brcmf_ampdu_rx_reorder - AMPDU receive reorder info
  *
- * @pktslots: dynamic allocated array for ordering AMPDU packets.
  * @flow_id: AMPDU flow identifier.
  * @cur_idx: last AMPDU index from firmware.
  * @exp_idx: expected next AMPDU index.
  * @max_idx: maximum amount of packets per AMPDU.
  * @pend_pkts: number of packets currently in @pktslots.
+ * @pktslots: array for ordering AMPDU packets.
  */
 struct brcmf_ampdu_rx_reorder {
-	struct sk_buff **pktslots;
 	u8 flow_id;
 	u8 cur_idx;
 	u8 exp_idx;
 	u8 max_idx;
 	u8 pend_pkts;
+	struct sk_buff *pktslots[];
 };
 
 /* Forward decls for struct brcmf_pub (see below) */
diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fwsignal.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fwsignal.c
index 36af81975855..0949e7975ff1 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fwsignal.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fwsignal.c
@@ -1673,7 +1673,6 @@ void brcmf_fws_rxreorder(struct brcmf_if *ifp, struct sk_buff *pkt)
 	struct sk_buff_head reorder_list;
 	struct sk_buff *pnext;
 	u8 flags;
-	u32 buf_size;
 
 	reorder_data = ((struct brcmf_skb_reorder_data *)pkt->cb)->reorder;
 	flow_id = reorder_data[BRCMF_RXREORDER_FLOWID_OFFSET];
@@ -1708,15 +1707,13 @@ void brcmf_fws_rxreorder(struct brcmf_if *ifp, struct sk_buff *pkt)
 	}
 	/* from here on we need a flow reorder instance */
 	if (rfi == NULL) {
-		buf_size = sizeof(*rfi);
 		max_idx = reorder_data[BRCMF_RXREORDER_MAXIDX_OFFSET];
 
-		buf_size += (max_idx + 1) * sizeof(pkt);
-
 		/* allocate space for flow reorder info */
 		brcmf_dbg(INFO, "flow-%d: start, maxidx %d\n",
 			  flow_id, max_idx);
-		rfi = kzalloc(buf_size, GFP_ATOMIC);
+		rfi = kzalloc(struct_size(rfi, pktslots, max_idx + 1),
+			      GFP_ATOMIC);
 		if (rfi == NULL) {
 			bphy_err(drvr, "failed to alloc buffer\n");
 			brcmf_netif_rx(ifp, pkt);
@@ -1724,7 +1721,6 @@ void brcmf_fws_rxreorder(struct brcmf_if *ifp, struct sk_buff *pkt)
 		}
 
 		ifp->drvr->reorder_flows[flow_id] = rfi;
-		rfi->pktslots = (struct sk_buff **)(rfi + 1);
 		rfi->max_idx = max_idx;
 	}
 	if (flags & BRCMF_RXREORDER_NEW_HOLE)  {
-- 
2.45.2