linux-kernel - Re: Re: [PATCH V4 net-bugfixs] net/ethernet: Update ret when ptp

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Date:   Thu, 12 Nov 2020 10:19:54 -0800
From:   Richard Cochran <richardcochran@...il.com>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     王擎 <wangqing@...o.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Grygorii Strashko <grygorii.strashko@...com>,
        "David S. Miller" <davem@...emloft.net>,
        Samuel Zou <zou_wei@...wei.com>,
        Kurt Kanzenbach <kurt@...utronix.de>,
        Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>,
        Networking <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Re: [PATCH V4 net-bugfixs] net/ethernet: Update ret when
 ptp_clock is ERROR

On Thu, Nov 12, 2020 at 09:25:12AM +0100, Arnd Bergmann wrote:
> This is not really getting any better. If Richard is worried about
> Kconfig getting changed here, I would suggest handling the
> case of PTP being disabled by returning an error early on in the
> function, like
> 
> struct am65_cpts *am65_cpts_create(struct device *dev, void __iomem *regs,
>                                    struct device_node *node)
> {
>         struct am65_cpts *cpts;
>         int ret, i;
> 
>         if (!IS_ENABLED(CONFIG_PTP_1588_CLOCK))
>                  return -ENODEV;

No, please, no.  That only adds confusion.  The NULL return value
already signals that the compile time support was missing.  That was
the entire point of this...

 * ptp_clock_register() - register a PTP hardware clock driver
 *
 * @info:   Structure describing the new clock.
 * @parent: Pointer to the parent device of the new clock.
 *
 * Returns a valid pointer on success or PTR_ERR on failure.  If PHC
 * support is missing at the configuration level, this function
 * returns NULL, and drivers are expected to gracefully handle that
 * case separately.

Thanks,
Richard