linux-kernel - Re: [PATCH RFC v2 1/6] ethtool: add interface to read Tx hardware timestamping statistics

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Date: Tue, 12 Mar 2024 16:53:46 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Rahul Rameshbabu <rrameshbabu@...dia.com>
Cc: ahmed.zaki@...el.com, aleksander.lobakin@...el.com,
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Subject: Re: [PATCH RFC v2 1/6] ethtool: add interface to read Tx hardware
 timestamping statistics

On Sat,  9 Mar 2024 00:44:35 -0800 Rahul Rameshbabu wrote:
> Multiple network devices that support hardware timestamping appear to have
> common behavior with regards to timestamp handling. Implement common Tx
> hardware timestamping statistics in a tx_stats struct_group. Common Rx
> hardware timestamping statistics can subsequently be implemented in a
> rx_stats struct_group for ethtool_ts_stats.

>  Documentation/netlink/specs/ethtool.yaml | 20 +++++++++
>  include/linux/ethtool.h                  | 21 ++++++++++
>  include/uapi/linux/ethtool_netlink.h     | 15 +++++++
>  net/ethtool/tsinfo.c                     | 52 +++++++++++++++++++++++-
>  4 files changed, 107 insertions(+), 1 deletion(-)

Feels like we should mention the new stats somehow in 
Documentation/networking/ethtool-netlink.rst

> diff --git a/Documentation/netlink/specs/ethtool.yaml b/Documentation/netlink/specs/ethtool.yaml
> index 197208f419dc..f99b003c78c0 100644
> --- a/Documentation/netlink/specs/ethtool.yaml
> +++ b/Documentation/netlink/specs/ethtool.yaml
> @@ -559,6 +559,21 @@ attribute-sets:
>        -
>          name: tx-lpi-timer
>          type: u32
> +  -
> +    name: ts-stat
> +    attributes:
> +      -
> +        name: pad
> +        type: pad

You can remove the pad entry, and...

> +      -
> +        name: tx-pkts
> +        type: u64

..use the uint type for the stats

> +      -
> +        name: tx-lost
> +        type: u64
> +      -
> +        name: tx-err
> +        type: u64
>    -
>      name: tsinfo
>      attributes:

> +/**
> + * struct ethtool_ts_stats - HW timestamping statistics
> + * @tx_stats: struct group for TX HW timestamping
> + *	@pkts: Number of packets successfully timestamped by the queried
> + *	      layer.
> + *	@lost: Number of packet timestamps that failed to get applied on a
> + *	      packet by the queried layer.
> + *	@err: Number of timestamping errors that occurred on the queried
> + *	     layer.

the kdocs for @lost and @err are not very clear

> + * @get_ts_stats: Query the device hardware timestamping statistics.

Let's copy & paste the "Drivers must not zero" text in here?
People seem to miss that requirement anyway, but at least we'll
have something to point at in review.

> +enum {
> +	ETHTOOL_A_TS_STAT_UNSPEC,
> +	ETHTOOL_A_TS_STAT_PAD,
> +
> +	ETHTOOL_A_TS_STAT_TX_PKT,			/* array, u64 */
> +	ETHTOOL_A_TS_STAT_TX_LOST,			/* array, u64 */
> +	ETHTOOL_A_TS_STAT_TX_ERR,			/* array, u64 */

I don't think these are arrays.

> +
> +	/* add new constants above here */
> +	__ETHTOOL_A_TS_STAT_CNT,
> +	ETHTOOL_A_TS_STAT_MAX = (__ETHTOOL_A_TS_STAT_CNT - 1)
> +
> +};