Subject: Re: [PATCH v2] extcon: fix extcon_get_extcon_dev() error handling
To:     Dan Carpenter <dan.carpenter@oracle.com>
Cc:     MyungJoo Ham <myungjoo.ham@samsung.com>,
        Guenter Roeck <linux@roeck-us.net>,
        Sebastian Reichel <sre@kernel.org>,
        Chen-Yu Tsai <wens@csie.org>,
        Hans de Goede <hdegoede@redhat.com>,
        Felipe Balbi <balbi@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Heikki Krogerus <heikki.krogerus@linux.intel.com>,
        linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
        linux-usb@vger.kernel.org, linux-omap@vger.kernel.org,
        kernel-janitors@vger.kernel.org
From:   Chanwoo Choi <cw00.choi@samsung.com>
Organization: Samsung Electronics
Message-ID: <1b4515cc-bddc-ff3d-7789-ea2eb66a2e4e@samsung.com>
Date:   Fri, 17 Dec 2021 10:31:47 +0900
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On 12/17/21 12:59 AM, Dan Carpenter wrote:
> On Thu, Dec 16, 2021 at 05:38:04PM +0900, Chanwoo Choi wrote:
>>>
>>> To be honest, I'm not sure how this differs from other functions which
>>> return -EPROBE_DEFER.  How do other functions guarantee they will only
>>> be called from probe()?
>>
>> If it is possible to know extcon_get_extcon_dev() will be only callled on probe,
>> it is no problem. But, it is not able to guarantee that extcon_get_extcon_dev()
>> is called on probe. Because of this reason, this issue should be handled in each device driver.
>>
>> -EPROBE_DEFER is only for probe step. If return -EPROBE_DEFER except for probe,
>> it is wrong return value.
> 
> The future is vast and unknowable.  We can't really future proof code
> and we should never try do that if it makes the code more complicated
> right now.
> 
> When Andy submitted basically the same patch as me three years ago we
> worried about future developers so we didn't merge his patch.  But
> three years later no non-probe() were introduced.  Meanwhile the bad API
> created bugs in the kernel for current users.

As you mentioned, there were no use case except for probe step.
OK. I agree this approach.


For merging this patch, need to get ack from power-supply and usb maintainer.
After getting the ack, I'll merge it. Thanks.

-- 
Best Regards,
Chanwoo Choi
Samsung Electronics