[RFC v1 02/22] net: ethtool: report max value for rx-buf-len

[Pavel Begunkov <asml.silence@gmail.com>]

From: Jakub Kicinski <kuba@kernel.org>

Unlike most of our APIs the rx-buf-len param does not have an associated
max value. In theory user could set this value pretty high, but in
practice most NICs have limits due to the width of the length fields
in the descriptors.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 Documentation/netlink/specs/ethtool.yaml                  | 4 ++++
 Documentation/networking/ethtool-netlink.rst              | 1 +
 drivers/net/ethernet/marvell/octeontx2/nic/otx2_ethtool.c | 3 ++-
 include/linux/ethtool.h                                   | 2 ++
 include/uapi/linux/ethtool_netlink_generated.h            | 1 +
 net/ethtool/rings.c                                       | 5 +++++
 6 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/Documentation/netlink/specs/ethtool.yaml b/Documentation/netlink/specs/ethtool.yaml
index 72a076b0e1b5..cb96b4e7093f 100644
--- a/Documentation/netlink/specs/ethtool.yaml
+++ b/Documentation/netlink/specs/ethtool.yaml
@@ -361,6 +361,9 @@ attribute-sets:
       -
         name: hds-thresh-max
         type: u32
+      -
+        name: rx-buf-len-max
+        type: u32
 
   -
     name: mm-stat
@@ -1811,6 +1814,7 @@ operations:
             - rx-jumbo
             - tx
             - rx-buf-len
+            - rx-buf-len-max
             - tcp-data-split
             - cqe-size
             - tx-push
diff --git a/Documentation/networking/ethtool-netlink.rst b/Documentation/networking/ethtool-netlink.rst
index eaa9c17a3cb1..b7a99dfdffa9 100644
--- a/Documentation/networking/ethtool-netlink.rst
+++ b/Documentation/networking/ethtool-netlink.rst
@@ -893,6 +893,7 @@ Kernel response contents:
   ``ETHTOOL_A_RINGS_RX_JUMBO``              u32     size of RX jumbo ring
   ``ETHTOOL_A_RINGS_TX``                    u32     size of TX ring
   ``ETHTOOL_A_RINGS_RX_BUF_LEN``            u32     size of buffers on the ring
+  ``ETHTOOL_A_RINGS_RX_BUF_LEN_MAX``        u32     max size of rx buffers
   ``ETHTOOL_A_RINGS_TCP_DATA_SPLIT``        u8      TCP header / data split
   ``ETHTOOL_A_RINGS_CQE_SIZE``              u32     Size of TX/RX CQE
   ``ETHTOOL_A_RINGS_TX_PUSH``               u8      flag of TX Push mode
diff --git a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_ethtool.c b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_ethtool.c
index 45b8c9230184..7bdef64926c8 100644
--- a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_ethtool.c
+++ b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_ethtool.c
@@ -376,6 +376,7 @@ static void otx2_get_ringparam(struct net_device *netdev,
 	ring->tx_max_pending = Q_COUNT(Q_SIZE_MAX);
 	ring->tx_pending = qs->sqe_cnt ? qs->sqe_cnt : Q_COUNT(Q_SIZE_4K);
 	kernel_ring->rx_buf_len = pfvf->hw.rbuf_len;
+	kernel_ring->rx_buf_len_max = 32768;
 	kernel_ring->cqe_size = pfvf->hw.xqe_size;
 }
 
@@ -398,7 +399,7 @@ static int otx2_set_ringparam(struct net_device *netdev,
 	/* Hardware supports max size of 32k for a receive buffer
 	 * and 1536 is typical ethernet frame size.
 	 */
-	if (rx_buf_len && (rx_buf_len < 1536 || rx_buf_len > 32768)) {
+	if (rx_buf_len && (rx_buf_len < 1536)) {
 		netdev_err(netdev,
 			   "Receive buffer range is 1536 - 32768");
 		return -EINVAL;
diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
index 5e0dd333ad1f..dd9f253a56ae 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.
+ * @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
  * @rx_push: The flag of rx push mode
@@ -89,6 +90,7 @@ enum {
  */
 struct kernel_ethtool_ringparam {
 	u32	rx_buf_len;
+	u32	rx_buf_len_max;
 	u8	tcp_data_split;
 	u8	tx_push;
 	u8	rx_push;
diff --git a/include/uapi/linux/ethtool_netlink_generated.h b/include/uapi/linux/ethtool_netlink_generated.h
index aa8ab5227c1e..1a76e6789e33 100644
--- a/include/uapi/linux/ethtool_netlink_generated.h
+++ b/include/uapi/linux/ethtool_netlink_generated.h
@@ -164,6 +164,7 @@ enum {
 	ETHTOOL_A_RINGS_TX_PUSH_BUF_LEN_MAX,
 	ETHTOOL_A_RINGS_HDS_THRESH,
 	ETHTOOL_A_RINGS_HDS_THRESH_MAX,
+	ETHTOOL_A_RINGS_RX_BUF_LEN_MAX,
 
 	__ETHTOOL_A_RINGS_CNT,
 	ETHTOOL_A_RINGS_MAX = (__ETHTOOL_A_RINGS_CNT - 1)
diff --git a/net/ethtool/rings.c b/net/ethtool/rings.c
index aeedd5ec6b8c..5e872ceab5dd 100644
--- a/net/ethtool/rings.c
+++ b/net/ethtool/rings.c
@@ -105,6 +105,9 @@ static int rings_fill_reply(struct sk_buff *skb,
 			  ringparam->tx_pending)))  ||
 	    (kr->rx_buf_len &&
 	     (nla_put_u32(skb, ETHTOOL_A_RINGS_RX_BUF_LEN, kr->rx_buf_len))) ||
+	    (kr->rx_buf_len_max &&
+	     (nla_put_u32(skb, ETHTOOL_A_RINGS_RX_BUF_LEN_MAX,
+			  kr->rx_buf_len_max))) ||
 	    (kr->tcp_data_split &&
 	     (nla_put_u8(skb, ETHTOOL_A_RINGS_TCP_DATA_SPLIT,
 			 kr->tcp_data_split))) ||
@@ -281,6 +284,8 @@ ethnl_set_rings(struct ethnl_req_info *req_info, struct genl_info *info)
 		err_attr = tb[ETHTOOL_A_RINGS_TX];
 	else if (kernel_ringparam.hds_thresh > kernel_ringparam.hds_thresh_max)
 		err_attr = tb[ETHTOOL_A_RINGS_HDS_THRESH];
+	else if (kernel_ringparam.rx_buf_len > kernel_ringparam.rx_buf_len_max)
+		err_attr = tb[ETHTOOL_A_RINGS_RX_BUF_LEN];
 	else
 		err_attr = NULL;
 	if (err_attr) {
-- 
2.49.0