netdev - [RFC PATCH v1 24/57] net: fec: Remove PAGE_SIZE compile-time constant assumption

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Message-ID: <20241014105912.3207374-24-ryan.roberts@arm.com>
Date: Mon, 14 Oct 2024 11:58:31 +0100
From: Ryan Roberts <ryan.roberts@....com>
To: "David S. Miller" <davem@...emloft.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Anshuman Khandual <anshuman.khandual@....com>,
	Ard Biesheuvel <ardb@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	David Hildenbrand <david@...hat.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Greg Marsden <greg.marsden@...cle.com>,
	Ivan Ivanov <ivan.ivanov@...e.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Kalesh Singh <kaleshsingh@...gle.com>,
	Marc Zyngier <maz@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Matthias Brugger <mbrugger@...e.com>,
	Miroslav Benes <mbenes@...e.cz>,
	Paolo Abeni <pabeni@...hat.com>,
	Wei Fang <wei.fang@....com>,
	Will Deacon <will@...nel.org>
Cc: Ryan Roberts <ryan.roberts@....com>,
	imx@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	netdev@...r.kernel.org
Subject: [RFC PATCH v1 24/57] net: fec: Remove PAGE_SIZE compile-time constant assumption

To prepare for supporting boot-time page size selection, refactor code
to remove assumptions about PAGE_SIZE being compile-time constant. Code
intended to be equivalent when compile-time page size is active.

Refactored "struct fec_enet_priv_rx_q" to use a flexible array member
for "rx_skb_info", since its length depends on PAGE_SIZE.

Signed-off-by: Ryan Roberts <ryan.roberts@....com>
---

***NOTE***
Any confused maintainers may want to read the cover note here for context:
https://lore.kernel.org/all/20241014105514.3206191-1-ryan.roberts@arm.com/

 drivers/net/ethernet/freescale/fec.h      | 3 ++-
 drivers/net/ethernet/freescale/fec_main.c | 5 +++--
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/freescale/fec.h b/drivers/net/ethernet/freescale/fec.h
index a19cb2a786fd2..afc8b3f360555 100644
--- a/drivers/net/ethernet/freescale/fec.h
+++ b/drivers/net/ethernet/freescale/fec.h
@@ -571,7 +571,6 @@ struct fec_enet_priv_tx_q {
 
 struct fec_enet_priv_rx_q {
 	struct bufdesc_prop bd;
-	struct  fec_enet_priv_txrx_info rx_skb_info[RX_RING_SIZE];
 
 	/* page_pool */
 	struct page_pool *page_pool;
@@ -580,6 +579,8 @@ struct fec_enet_priv_rx_q {
 
 	/* rx queue number, in the range 0-7 */
 	u8 id;
+
+	struct  fec_enet_priv_txrx_info rx_skb_info[];
 };
 
 struct fec_stop_mode_gpr {
diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index a923cb95cdc62..b9214c12d537e 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -3339,6 +3339,8 @@ static int fec_enet_alloc_queue(struct net_device *ndev)
 	int i;
 	int ret = 0;
 	struct fec_enet_priv_tx_q *txq;
+	size_t rxq_sz = struct_size(fep->rx_queue[0], rx_skb_info, RX_RING_SIZE);
+
 
 	for (i = 0; i < fep->num_tx_queues; i++) {
 		txq = kzalloc(sizeof(*txq), GFP_KERNEL);
@@ -3364,8 +3366,7 @@ static int fec_enet_alloc_queue(struct net_device *ndev)
 	}
 
 	for (i = 0; i < fep->num_rx_queues; i++) {
-		fep->rx_queue[i] = kzalloc(sizeof(*fep->rx_queue[i]),
-					   GFP_KERNEL);
+		fep->rx_queue[i] = kzalloc(rxq_sz, GFP_KERNEL);
 		if (!fep->rx_queue[i]) {
 			ret = -ENOMEM;
 			goto alloc_failed;
-- 
2.43.0