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

Andy Shevchenko
2018-11-14T10:20:04Z

On Wed, Nov 14, 2018 at 11:48 AM Chanwoo Choi <cw00.choi@samsung.com> wrote:
>
> On 2018년 11월 14일 18:36, Andy Shevchenko wrote:
> > On Wed, Nov 14, 2018 at 06:13:37PM +0900, Chanwoo Choi wrote:
> >> On 2018년 11월 14일 17:35, Andy Shevchenko wrote:
> >>> On Wed, Nov 14, 2018 at 1:53 AM Chanwoo Choi <cw00.choi@samsung.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?
> >>
> >> The extcon core don't know the caller situation is in either probe() or other position
> >> in the caller driver. The caller driver should decide the kind of error value
> >> by using the return value of extcon_get_extcon_dev().
> >>
> >> extcon_get_extcon_dev() function cannot be modified for only one case.
> >> If some device driver call extcon_get_extcon_dev() out of probe() fuction,
> >> EPROBE_DEFER is not always correct.
> >
> > I agree with this, but look at the current state of affairs. All users do the same.
> > If we need to have another case we may consider this later.
>
> Because we know the potential wrong case of this change, I can't agree this change.
> If extcon_get_extcon_dev() returns ENODEV instead of EPROBE_DEFER,
> it is clear and then there are no problem on both current and future.

Changing NULL to -ENODEV is a trading bad to worse.
I would not go that way, so, it's your call.

> > API inside the kernel are not carved in the stone.

Only can repeat myself (see above). While I see *theoretical*
rationale on your side, mine has *practical* proofs.
So, I'm giving up on this and will duplicate same what it's done in 4
current callers.

--
With Best Regards,
Andy Shevchenko