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

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Date:   Thu, 12 Nov 2020 09:25:12 +0100
From:   Arnd Bergmann <arnd@...nel.org>
To:     王擎 <wangqing@...o.com>
Cc:     Jakub Kicinski <kuba@...nel.org>,
        Richard Cochran <richardcochran@...il.com>,
        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 2:48 AM 王擎 <wangqing@...o.com> wrote:
> >> On Wed, Nov 11, 2020 at 03:24:33PM +0200, Grygorii Strashko wrote:
> >
> >I don't think v1 builds cleanly folks (not 100% sure, cpts is not
> >compiled on x86):
> >
> >               ret = cpts->ptp_clock ? cpts->ptp_clock : (-ENODEV);
> >
> >ptp_clock is a pointer, ret is an integer, right?
>
> yeah, I will modify like: ret = cpts->ptp_clock ? PTR_ERR(cpts->ptp_clock) : -ENODEV;

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;

Then you can replace the broken IS_ERR_OR_NULL() path with
a simpler IS_ERR() case and keep the rest of the function readable.

> >Grygorii, would you mind sending a correct patch in so Wang Qing can
> >see how it's done? I've been asking for a fixes tag multiple times
> >already :(
>
> I still don't quite understand what a fixes tag means，
> can you tell me how to do this, thanks.

This identifies which patch introduced the problem you are fixing
originally. If you add an alias in your ~/.gitconfig such as

[alias]
        fixes = show --format='Fixes: %h (\"%s\")' -s

then running

$ git fixes f6bd59526c
produces this line:

Fixes: f6bd59526ca5 ("net: ethernet: ti: introduce am654 common
platform time sync driver")

which you can add to the changelog, just above the Signed-off-by
lines.

      Arnd