Re: [PATCH net-next 2/2] netlink: specs: tcp_metrics: drop the RTT shift instructions

[Hangbin Liu <hangbin.liu@linux.dev>]

On Sat, Sep 12, 2026 at 04:43:37PM -0700, Jakub Kicinski wrote:
> All four RTT attributes tell the reader to left-shift, which inflates the
> value by 16 to 64 times, and the two usec ones say the result is in msecs.
> The attributes carry srtt_us and mdev_us, which hold 3 and 2 fractional
> bits. The shift to get the integer part would be a right shift.
> 
> Drop the instructions instead of turning them around. The number of
> fractional bits is the part worth documenting, whether to shift, divide or
> convert to a double is up to the caller.
> 
> While at it fix the acronym on the two variance attributes.
> 
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> ---
>  Documentation/netlink/specs/tcp_metrics.yaml | 12 ++++--------
>  1 file changed, 4 insertions(+), 8 deletions(-)
> 
> diff --git a/Documentation/netlink/specs/tcp_metrics.yaml b/Documentation/netlink/specs/tcp_metrics.yaml
> index 1d365908084d..779e8a22b765 100644
> --- a/Documentation/netlink/specs/tcp_metrics.yaml
> +++ b/Documentation/netlink/specs/tcp_metrics.yaml
> @@ -93,14 +93,12 @@ kernel-policy: global
>          name: rtt
>          type: u32
>          doc: |
> -          Round Trip Time (RTT), in msecs with 3 bits fractional
> -          (left-shift by 3 to get the msec value).
> +          Round Trip Time (RTT), in msecs with 3 bits fractional.
>        -
>          name: rttvar
>          type: u32
>          doc: |
> -          Round Trip Time VARiance (RTT), in msecs with 2 bits fractional
> -          (left-shift by 2 to get the msec value).
> +          Round Trip Time VARiance (RTTVAR), in msecs with 2 bits fractional.
>        -
>          name: ssthresh
>          type: u32
> @@ -117,14 +115,12 @@ kernel-policy: global
>          name: rtt-us
>          type: u32
>          doc: |
> -          Round Trip Time (RTT), in usecs, with 3 bits fractional
> -          (left-shift by 3 to get the msec value).
> +          Round Trip Time (RTT), in usecs, with 3 bits fractional.
>        -
>          name: rttvar-us
>          type: u32
>          doc: |
> -          Round Trip Time (RTT), in usecs, with 2 bits fractional
> -          (left-shift by 3 to get the msec value).
> +          Round Trip Time VARiance (RTTVAR), in usecs, with 2 bits fractional.
>  
>  operations:
>    list:
> -- 
> 2.55.0
> 

Reviewed-by: Hangbin Liu <liuhangbin@kylinos.cn>