linux-kernel - Re: [PATCH net-next v3 3/4] net: stmmac: add Rx HWTS metadata to XDP receive pkt

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Message-ID: <CAKH8qBtXTAZr5r1VC9ynSvGv5jWMD54d=-2qmBc9Zr3ui9HnEg@mail.gmail.com>
Date:   Wed, 12 Apr 2023 14:45:33 -0700
From:   Stanislav Fomichev <sdf@...gle.com>
To:     Jacob Keller <jacob.e.keller@...el.com>
Cc:     Song Yoong Siang <yoong.siang.song@...el.com>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Jose Abreu <joabreu@...opsys.com>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Alexander Duyck <alexanderduyck@...com>,
        Ong Boon Leong <boon.leong.ong@...el.com>,
        netdev@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        bpf@...r.kernel.org, xdp-hints@...-project.net
Subject: Re: [PATCH net-next v3 3/4] net: stmmac: add Rx HWTS metadata to XDP
 receive pkt

On Wed, Apr 12, 2023 at 1:56 PM Jacob Keller <jacob.e.keller@...el.com> wrote:
>
>
>
> On 4/12/2023 10:00 AM, Stanislav Fomichev wrote:
> > On 04/12, Song Yoong Siang wrote:
> >> Add receive hardware timestamp metadata support via kfunc to XDP receive
> >> packets.
> >>
> >> Suggested-by: Stanislav Fomichev <sdf@...gle.com>
> >> Signed-off-by: Song Yoong Siang <yoong.siang.song@...el.com>
> >> ---
> >>  drivers/net/ethernet/stmicro/stmmac/stmmac.h  |  3 +++
> >>  .../net/ethernet/stmicro/stmmac/stmmac_main.c | 26 ++++++++++++++++++-
> >>  2 files changed, 28 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac.h b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
> >> index ac8ccf851708..826ac0ec88c6 100644
> >> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac.h
> >> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
> >> @@ -94,6 +94,9 @@ struct stmmac_rx_buffer {
> >>
> >>  struct stmmac_xdp_buff {
> >>      struct xdp_buff xdp;
> >> +    struct stmmac_priv *priv;
> >> +    struct dma_desc *p;
> >> +    struct dma_desc *np;
> >>  };
> >>
> >>  struct stmmac_rx_queue {
> >> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> >> index f7bbdf04d20c..ed660927b628 100644
> >> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> >> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> >> @@ -5315,10 +5315,15 @@ static int stmmac_rx(struct stmmac_priv *priv, int limit, u32 queue)
> >>
> >>                      xdp_init_buff(&ctx.xdp, buf_sz, &rx_q->xdp_rxq);
> >>                      xdp_prepare_buff(&ctx.xdp, page_address(buf->page),
> >> -                                     buf->page_offset, buf1_len, false);
> >> +                                     buf->page_offset, buf1_len, true);
> >>
> >>                      pre_len = ctx.xdp.data_end - ctx.xdp.data_hard_start -
> >>                                buf->page_offset;
> >> +
> >> +                    ctx.priv = priv;
> >> +                    ctx.p = p;
> >> +                    ctx.np = np;
> >> +
> >>                      skb = stmmac_xdp_run_prog(priv, &ctx.xdp);
> >>                      /* Due xdp_adjust_tail: DMA sync for_device
> >>                       * cover max len CPU touch
> >> @@ -7071,6 +7076,23 @@ void stmmac_fpe_handshake(struct stmmac_priv *priv, bool enable)
> >>      }
> >>  }
> >>
> >> +static int stmmac_xdp_rx_timestamp(const struct xdp_md *_ctx, u64 *timestamp)
> >> +{
> >> +    const struct stmmac_xdp_buff *ctx = (void *)_ctx;
> >> +
> >> +    *timestamp = 0;
> >> +    stmmac_get_rx_hwtstamp(ctx->priv, ctx->p, ctx->np, timestamp);
> >> +
> >
> > [..]
> >
> >> +    if (*timestamp)
> >
> > Nit: does it make sense to change stmmac_get_rx_hwtstamp to return bool
> > to indicate success/failure? Then you can do:
> >
> > if (!stmmac_get_rx_hwtstamp())
> >       reutrn -ENODATA;
>
> I would make it return the -ENODATA directly since typically bool
> true/false functions have names like "stmmac_has_rx_hwtstamp" or similar
> name that infers you're answering a true/false question.
>
> That might also let you avoid zeroing the timestamp value first?

SGTM!

> Thanks,
> Jake