linux-kernel - Re: [PATCH net 1/2] net: fec_ptp: add clock rate zero check

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Message-ID: <20210616132859.GE22278@shell.armlinux.org.uk>
Date:   Wed, 16 Jun 2021 14:28:59 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Joakim Zhang <qiangqing.zhang@....com>
Cc:     "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "peppe.cavallaro@...com" <peppe.cavallaro@...com>,
        "alexandre.torgue@...s.st.com" <alexandre.torgue@...s.st.com>,
        "joabreu@...opsys.com" <joabreu@...opsys.com>,
        "mcoquelin.stm32@...il.com" <mcoquelin.stm32@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-stm32@...md-mailman.stormreply.com" 
        <linux-stm32@...md-mailman.stormreply.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        dl-linux-imx <linux-imx@....com>
Subject: Re: [PATCH net 1/2] net: fec_ptp: add clock rate zero check

Hi Joakim,

On Wed, Jun 16, 2021 at 11:40:29AM +0000, Joakim Zhang wrote:
> Do you mean that print an error message then return directly? It seems better.

Nearly - one has to ensure that the cleanup functions don't provoke a
crash though. I notice fec_ptp_stop() makes use of fep->time_keep
and also fep->ptp_clock.

fep->time_keep is initialised after where you need to test for zero
cycle_speed, so the initialisation would need moving earlier.

I would have thought that ftp->ptp_clock should be NULL, so that's
probably okay, but should be checked that this assumption is in fact
true.

> if (!fep->cycle_speed) {
> 	dev_err(&fep->pdev->dev, "PTP clock rate should not be zero!\n");

I'd still say something like "PTP clock rate should not be zero,
disabling PTP" - say what's wrong and what we are doing. Also,
please avoid exclaimation marks in error messages.

Thanks.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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