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From:   Arnd Bergmann <arnd@kernel.org>
Date:   Sat, 14 Nov 2020 22:16:49 +0100
Message-ID: <CAK8P3a3mM3CF889Fi4COr1A9LDDi74_93xnwt9rZkky5Zd5www@mail.gmail.com>
Subject: Re: Re: [PATCH V4 net-bugfixs] net/ethernet: Update ret when
 ptp_clock is ERROR
To:     Richard Cochran <richardcochran@gmail.com>
Cc:     =?UTF-8?B?546L5pOO?= <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>
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On Sat, Nov 14, 2020 at 4:14 PM Richard Cochran
<richardcochran@gmail.com> wrote:
>
> On Fri, Nov 13, 2020 at 05:21:43PM +0100, Arnd Bergmann wrote:
> > I've prototyped a patch that I think makes this more sensible
> > again: https://pastebin.com/AQ5nWS9e
>
> I like the behavior described in the text.
>
> Instead of this ...
>
>      - if a built-in driver calls PTP interface functions but fails
>        to select HAVE_PTP_1588_CLOCK or depend on PTP_1588_CLOCK,
>        and PTP support is a loadable module, we get a link error
>        instead of having an unusable clock.
>
> how about simply deleting the #else clause of
>
>     --- a/include/linux/ptp_clock_kernel.h
>     +++ b/include/linux/ptp_clock_kernel.h
>     @@ -173,7 +173,7 @@ struct ptp_clock_event {
>       };
>      };
>
>     -#if IS_REACHABLE(CONFIG_PTP_1588_CLOCK)
>     +#if IS_ENABLED(CONFIG_PTP_1588_CLOCK)
>
> so that invalid configurations throw a compile time error instead?

I was trying to still allow PTP clocks to be disabled, either when
building a kernel that doesn't need it, or when posix timers are
disabled. Leaving out the #else path would break all drivers that
have PTP support in the main ethernet driver file rather than
conditionally compiling it based on a Kconfig symbol that depends
on CONFIG_PTP_1588_CLOCK.

       Arnd