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

[Chanwoo Choi <cw00.choi@samsung.com>]

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.

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