[xdp-hints] Re: [PATCH bpf-next v3 2/3] net: stmmac: add Launch Time support to XDP ZC

[Jesper Dangaard Brouer <hawk@kernel.org>]

On 12/3/23 17:51, Song Yoong Siang wrote:
> This patch enables Launch Time (Time-Based Scheduling) support to XDP zero
> copy via XDP Tx metadata framework.
> 
> Signed-off-by: Song Yoong Siang<yoong.siang.song@intel.com>
> ---
>   drivers/net/ethernet/stmicro/stmmac/stmmac.h      |  2 ++

As requested before, I think we need to see another driver implementing 
this.

I propose driver igc and chip i225.

The interesting thing for me is to see how the LaunchTime max 1 second
into the future[1] is handled code wise. One suggestion is to add a 
section to Documentation/networking/xsk-tx-metadata.rst per driver that 
mentions/documents these different hardware limitations.  It is natural 
that different types of hardware have limitations.  This is a close-to 
hardware-level abstraction/API, and IMHO as long as we document the 
limitations we can expose this API without too many limitations for more 
capable hardware.

  [1] 
https://github.com/xdp-project/xdp-project/blob/master/areas/tsn/code01_follow_qdisc_TSN_offload.org#setup-code-driver-igb

This stmmac driver and Intel Tiger Lake CPU must also have some limit on 
how long into the future it will/can schedule packets?


People from xdp-hints list must make their voice hear if they want i210 
and igb driver support, because it have even-more hardware limitations, 
see [1] (E.g. only TX queue 0 and 1 supports LaunchTime). BUT I know 
some have this hardware in production and might be motivated to get a 
functioning driver with this feature?

--Jesper