netdev - Re: [PATCH net-next v1 4/4] net: lan966x: generate software timestamp just before the doorbell

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Message-ID: <CAL+tcoBq_-COOvjk53oO1w=ReWQzMivAmQPF4F20vAF_Bd7sCg@mail.gmail.com>
Date: Thu, 8 May 2025 22:16:19 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Vladimir Oltean <olteanv@...il.com>
Cc: Horatiu Vultur <horatiu.vultur@...rochip.com>, irusskikh@...vell.com, 
	andrew+netdev@...n.ch, bharat@...lsio.com, ayush.sawal@...lsio.com, 
	UNGLinuxDriver@...rochip.com, mcoquelin.stm32@...il.com, 
	alexandre.torgue@...s.st.com, davem@...emloft.net, edumazet@...gle.com, 
	kuba@...nel.org, pabeni@...hat.com, horms@...nel.org, sgoutham@...vell.com, 
	willemb@...gle.com, linux-arm-kernel@...ts.infradead.org, 
	netdev@...r.kernel.org, Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH net-next v1 4/4] net: lan966x: generate software timestamp
 just before the doorbell

On Thu, May 8, 2025 at 8:40 PM Vladimir Oltean <olteanv@...il.com> wrote:
>
> On Thu, May 08, 2025 at 08:22:39PM +0800, Jason Xing wrote:
> > Thanks for the kind reply.
> >
> > It looks like how to detect depends on how the bpf prog is written?
> > Mostly depends on how the writer handles this data part. Even though
> > we don't guarantee on how to ask users/admins to write/adjust their
> > bpf codes, it's not that convenient for them if this patch is applied,
> > to be frank. I'm not pushing you to accept this patch, just curious on
> > "how and why". Now I can guess why you're opposed to it....
>
> The BPF program is not user-generated, it is run in the context of the
> function you're moving.
>
> skb_tx_timestamp()
> -> skb_clone_tx_timestamp()
>    -> classify()
>       -> ptp_classify_raw()
>          -> bpf_prog_run(ptp_insns, skb)

Right, I'll drop this patch from the series then.

Thanks,
Jason