linux-kernel - Re: [PATCH v1 2/5] extcon: Return -EPROBE_DEFER when extcon device is not found

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Message-ID: <CAHp75Vfe586+tr5mUdSHv4ehmpi0KwS_m+UC0tfFHrdXwKhkig@mail.gmail.com>
Date:   Wed, 14 Nov 2018 10:35:38 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Chanwoo Choi <cw00.choi@...sung.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        USB <linux-usb@...r.kernel.org>, Felipe Balbi <balbi@...nel.org>,
        Guenter Roeck <linux@...ck-us.net>,
        "Krogerus, Heikki" <heikki.krogerus@...ux.intel.com>,
        rogerq@...com, Linux PM <linux-pm@...r.kernel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Sebastian Reichel <sre@...nel.org>,
        Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
        Darren Hart <dvhart@...radead.org>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Chen-Yu Tsai <wens@...e.org>,
        Hans de Goede <hdegoede@...hat.com>
Subject: Re: [PATCH v1 2/5] extcon: Return -EPROBE_DEFER when extcon device is
 not found

On Wed, Nov 14, 2018 at 1:53 AM Chanwoo Choi <cw00.choi@...sung.com> wrote:

> I was thinking about again to change from NULL to EPROBE_DEFER.
>
> extcon_get_extcon_dev() function was almost called in the probe function.
> But, this function might be called on other position instead of probe.

*Might be* sounds like a theoretical thing, care to share what is in you mind?
Current users and more important the new coming one are *all* doing the same.

> ENODEV is more correct error instead of EPROBE_DEFER.

So, you are proposing to continue duplicating conversion from ENODEV
to EPROBE_DEFER in *each* caller?

> Sorry. I'll withdraw my opinion related acked-by tag until we are clarifying it.

I honestly don't know what to clarify here.

When we would have a real case we can change API correspondingly.
For now, the score is 5:0 with use cases in practice.

> On 2018년 11월 12일 09:24, Chanwoo Choi wrote:
> > On 2018년 11월 11일 03:10, Andy Shevchenko wrote:
> >> All current users of extcon_get_extcon_dev() API considers
> >> an extcon device a mandatory to appear. Thus, they all convert
> >> NULL pointer to -EPROBE_DEFER error code.
> >>
> >> There is one more caller anticipated with the same requirements.
> >>
> >> To decrease a code duplication and a burden to the callers,
> >> return -EPROBE_DEFER directly from extcon_get_extcon_dev().

-- 
With Best Regards,
Andy Shevchenko