netdev - Re: [RFC v1 03/22] net: use zero value to restore rx_buf

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Message-ID: <aIhWLcnu884VkNDO@opensource>
Date: Tue, 29 Jul 2025 05:03:41 +0000
From: Subbaraya Sundeep <sbhatta@...vell.com>
To: Pavel Begunkov <asml.silence@...il.com>
CC: Jakub Kicinski <kuba@...nel.org>, <netdev@...r.kernel.org>,
        <io-uring@...r.kernel.org>, Eric Dumazet <edumazet@...gle.com>,
        Willem de
 Bruijn <willemb@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>, <andrew+netdev@...n.ch>,
        <horms@...nel.org>, <davem@...emloft.net>, <sdf@...ichev.me>,
        <almasrymina@...gle.com>, <dw@...idwei.uk>,
        <michael.chan@...adcom.com>, <dtatulea@...dia.com>,
        <ap420073@...il.com>
Subject: Re: [RFC v1 03/22] net: use zero value to restore rx_buf_len to
 default

LGTM.

Thanks,
Sundeep

On 2025-07-28 at 11:04:07, Pavel Begunkov (asml.silence@...il.com) wrote:
> 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 b7a99dfdffa9..723f8e1a33a7 100644
> --- a/Documentation/networking/ethtool-netlink.rst
> +++ b/Documentation/networking/ethtool-netlink.rst
> @@ -974,7 +974,7 @@ threshold value, header and data will be split.
>  ``ETHTOOL_A_RINGS_RX_BUF_LEN`` controls the size of the buffer chunks driver
>  uses to receive packets. If the device uses different memory polls for headers
>  and payload this setting may control the size of the header buffers but 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 7bdef64926c8..1a74a7b81ac1 100644
> --- a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_ethtool.c
> +++ b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_ethtool.c
> @@ -396,6 +396,9 @@ 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 dd9f253a56ae..bbc5c485bfbf 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
>