linux-kernel - [PATCH net-next v4 04/24] net: use zero value to restore rx_buf

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Message-ID: <271820dbf61d9de6f62440598a318926aa96f9cd.1760364551.git.asml.silence@gmail.com>
Date: Mon, 13 Oct 2025 15:54:06 +0100
From: Pavel Begunkov <asml.silence@...il.com>
To: netdev@...r.kernel.org
Cc: Andrew Lunn <andrew@...n.ch>,
	Jakub Kicinski <kuba@...nel.org>,
	davem@...emloft.net,
	Eric Dumazet <edumazet@...gle.com>,
	Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>,
	Donald Hunter <donald.hunter@...il.com>,
	Michael Chan <michael.chan@...adcom.com>,
	Pavan Chebbi <pavan.chebbi@...adcom.com>,
	Jesper Dangaard Brouer <hawk@...nel.org>,
	John Fastabend <john.fastabend@...il.com>,
	Stanislav Fomichev <sdf@...ichev.me>,
	Joshua Washington <joshwash@...gle.com>,
	Harshitha Ramamurthy <hramamurthy@...gle.com>,
	Jian Shen <shenjian15@...wei.com>,
	Salil Mehta <salil.mehta@...wei.com>,
	Jijie Shao <shaojijie@...wei.com>,
	Sunil Goutham <sgoutham@...vell.com>,
	Geetha sowjanya <gakula@...vell.com>,
	Subbaraya Sundeep <sbhatta@...vell.com>,
	hariprasad <hkelam@...vell.com>,
	Bharat Bhushan <bbhushan2@...vell.com>,
	Saeed Mahameed <saeedm@...dia.com>,
	Tariq Toukan <tariqt@...dia.com>,
	Mark Bloch <mbloch@...dia.com>,
	Leon Romanovsky <leon@...nel.org>,
	Alexander Duyck <alexanderduyck@...com>,
	kernel-team@...a.com,
	Ilias Apalodimas <ilias.apalodimas@...aro.org>,
	Joe Damato <joe@...a.to>,
	David Wei <dw@...idwei.uk>,
	Willem de Bruijn <willemb@...gle.com>,
	Mina Almasry <almasrymina@...gle.com>,
	Pavel Begunkov <asml.silence@...il.com>,
	Breno Leitao <leitao@...ian.org>,
	Dragos Tatulea <dtatulea@...dia.com>,
	linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org,
	linux-rdma@...r.kernel.org,
	Jonathan Corbet <corbet@....net>
Subject: [PATCH net-next v4 04/24] net: use zero value to restore rx_buf_len to default

From: Jakub Kicinski <kuba@...nel.org>

Distinguish between rx_buf_len being driver default vs user config.
Use 0 as a special value meaning "unset" or "restore driver default".
This will be necessary later on to configure it per-queue, but
the ability to restore defaults may be useful in itself.

Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
---
 Documentation/networking/ethtool-netlink.rst              | 2 +-
 drivers/net/ethernet/marvell/octeontx2/nic/otx2_ethtool.c | 3 +++
 include/linux/ethtool.h                                   | 1 +
 net/ethtool/rings.c                                       | 2 +-
 4 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/Documentation/networking/ethtool-netlink.rst b/Documentation/networking/ethtool-netlink.rst
index d96a6292f37b..41d4d81a86d1 100644
--- a/Documentation/networking/ethtool-netlink.rst
+++ b/Documentation/networking/ethtool-netlink.rst
@@ -983,7 +983,7 @@ threshold value, header and data will be split.
 ``ETHTOOL_A_RINGS_RX_BUF_LEN`` controls the size of the buffers driver
 uses to receive packets. If the device uses different buffer pools for
 headers and payload (due to HDS, HW-GRO etc.) this setting must
-control the size of the payload buffers.
+control the size of the payload buffers. Setting to 0 restores driver default.
 
 CHANNELS_GET
 ============
diff --git a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_ethtool.c b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_ethtool.c
index 19bcf52330d4..ada6244445da 100644
--- a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_ethtool.c
+++ b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_ethtool.c
@@ -397,6 +397,9 @@ static int otx2_set_ringparam(struct net_device *netdev,
 	if (ring->rx_mini_pending || ring->rx_jumbo_pending)
 		return -EINVAL;
 
+	if (!rx_buf_len)
+		rx_buf_len = OTX2_DEFAULT_RBUF_LEN;
+
 	/* Hardware supports max size of 32k for a receive buffer
 	 * and 1536 is typical ethernet frame size.
 	 */
diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
index 26ef5ffdc435..0e6023df3ee9 100644
--- a/include/linux/ethtool.h
+++ b/include/linux/ethtool.h
@@ -77,6 +77,7 @@ enum {
 /**
  * struct kernel_ethtool_ringparam - RX/TX ring configuration
  * @rx_buf_len: Current length of buffers on the rx ring.
+ *		Setting to 0 means reset to driver default.
  * @rx_buf_len_max: Max length of buffers on the rx ring.
  * @tcp_data_split: Scatter packet headers and data to separate buffers
  * @tx_push: The flag of tx push mode
diff --git a/net/ethtool/rings.c b/net/ethtool/rings.c
index 5e872ceab5dd..628546a1827b 100644
--- a/net/ethtool/rings.c
+++ b/net/ethtool/rings.c
@@ -139,7 +139,7 @@ const struct nla_policy ethnl_rings_set_policy[] = {
 	[ETHTOOL_A_RINGS_RX_MINI]		= { .type = NLA_U32 },
 	[ETHTOOL_A_RINGS_RX_JUMBO]		= { .type = NLA_U32 },
 	[ETHTOOL_A_RINGS_TX]			= { .type = NLA_U32 },
-	[ETHTOOL_A_RINGS_RX_BUF_LEN]            = NLA_POLICY_MIN(NLA_U32, 1),
+	[ETHTOOL_A_RINGS_RX_BUF_LEN]            = { .type = NLA_U32 },
 	[ETHTOOL_A_RINGS_TCP_DATA_SPLIT]	=
 		NLA_POLICY_MAX(NLA_U8, ETHTOOL_TCP_DATA_SPLIT_ENABLED),
 	[ETHTOOL_A_RINGS_CQE_SIZE]		= NLA_POLICY_MIN(NLA_U32, 1),
-- 
2.49.0