linux-kernel - Re: [PATCH net-next v3 1/2] drivers: net: stmmac: handle start time set in the past for flexible PPS

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Message-ID: <57196414-5ab5-41b7-b2e3-ff6831589811@foss.st.com>
Date: Fri, 29 Aug 2025 12:51:40 +0200
From: Gatien CHEVALLIER <gatien.chevallier@...s.st.com>
To: Jakub Kicinski <kuba@...nel.org>
CC: Andrew Lunn <andrew+netdev@...n.ch>,
        "David S. Miller"
	<davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>, Paolo Abeni
	<pabeni@...hat.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        "Alexandre
 Torgue" <alexandre.torgue@...s.st.com>,
        Richard Cochran
	<richardcochran@...il.com>,
        Rob Herring <robh@...nel.org>,
        "Krzysztof
 Kozlowski" <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>, <netdev@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <devicetree@...r.kernel.org>
Subject: Re: [PATCH net-next v3 1/2] drivers: net: stmmac: handle start time
 set in the past for flexible PPS



On 8/28/25 04:31, Jakub Kicinski wrote:
> On Wed, 27 Aug 2025 13:04:58 +0200 Gatien Chevallier wrote:
>> +		curr_time = ns_to_timespec64(ns);
>> +		if (target_ns < ns + PTP_SAFE_TIME_OFFSET_NS) {
>> +			cfg->start = timespec64_add_safe(cfg->start, curr_time);
> 
> Is there a strong reason to use timespec64_add_safe()?
> It's not exported to modules:
> ERROR: modpost: "timespec64_add_safe" [drivers/net/ethernet/stmicro/stmmac/stmmac.ko] undefined!

Hello Jakub,

you're absolutely right. I don't know how I did not encounter the build
error while performing some tests, that I'm getting now as well.

The handling of overflows is already done in that function. Either
I can make a patch to export the symbol or handle the computation in the
driver. What do you think is best?

Cheers,
Gatien