From: Arnd Bergmann <arnd@kernel.org>
To: Richard Cochran <richardcochran@gmail.com>
Cc: 王擎 <wangqing@vivo.com>, "Jakub Kicinski" <kuba@kernel.org>,
"Grygorii Strashko" <grygorii.strashko@ti.com>,
"David S. Miller" <davem@davemloft.net>,
"Samuel Zou" <zou_wei@huawei.com>,
"Kurt Kanzenbach" <kurt@linutronix.de>,
"Ivan Khoronzhuk" <ivan.khoronzhuk@linaro.org>,
Networking <netdev@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: Re: [PATCH V4 net-bugfixs] net/ethernet: Update ret when ptp_clock is ERROR
Date: Thu, 12 Nov 2020 22:21:21 +0100 [thread overview]
Message-ID: <CAK8P3a1pHpweXP+2mp7bdg2GvU5kk4NASsu4MQCRPtK-VpuXSA@mail.gmail.com> (raw)
In-Reply-To: <20201112181954.GD21010@hoboy.vegasvil.org>
On Thu, Nov 12, 2020 at 7:19 PM Richard Cochran
<richardcochran@gmail.com> wrote:
>
> 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.
The problem is that the caller doesn't handle that case gracefully,
but it instead wants to return an error after all. I don't see a good
solution either; as far as I'm concerned we should never be building
code that fails if PTP_1588_CLOCK is disabled when it cannot
do anything sensible in that configuration.
I agree that the 'imply' keyword in Kconfig is what made this a
lot worse, and it would be best to replace that with normal
dependencies.
It would be possible to have a ptp_clock_register_optional()
interface in addition to ptp_clock_register(), which could then
be changed to return an error. Some other subsystems follow
this pattern, but it's not any less confusing either.
Arnd
next prev parent reply other threads:[~2020-11-12 21:21 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-11 9:24 [PATCH V4 net-bugfixs] net/ethernet: Update ret when ptp_clock is ERROR Wang Qing
2020-11-11 12:32 ` Richard Cochran
2020-11-11 13:24 ` Grygorii Strashko
2020-11-11 13:55 ` Richard Cochran
2020-11-11 16:00 ` Jakub Kicinski
2020-11-12 1:15 ` 王擎
2020-11-12 1:32 ` Jakub Kicinski
2020-11-12 2:48 ` 王擎
2020-11-12 4:23 ` Jakub Kicinski
2020-11-12 8:25 ` Arnd Bergmann
2020-11-12 10:05 ` Grygorii Strashko
2020-11-12 18:14 ` Richard Cochran
2020-11-12 18:19 ` Richard Cochran
2020-11-12 21:21 ` Arnd Bergmann [this message]
2020-11-12 23:27 ` Richard Cochran
2020-11-13 16:21 ` Arnd Bergmann
2020-11-14 15:14 ` Richard Cochran
2020-11-14 21:16 ` Arnd Bergmann
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