linux-kernel - Re: [PATCH v2] extcon: fix extcon_get_extcon

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Date:   Thu, 16 Dec 2021 11:05:58 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Chanwoo Choi <cw00.choi@...sung.com>
Cc:     MyungJoo Ham <myungjoo.ham@...sung.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Sebastian Reichel <sre@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-usb@...r.kernel.org, linux-omap@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH v2] extcon: fix extcon_get_extcon_dev() error handling

On Thu, Dec 16, 2021 at 05:24:30PM +0900, Chanwoo Choi wrote:
> On 12/16/21 4:52 PM, Dan Carpenter wrote:
> > On Thu, Dec 16, 2021 at 03:39:46PM +0900, Chanwoo Choi wrote:
> >> Hi Dan,
> >>
> >> First of all,  sorry for late reply.
> >>
> >> There is one issue. About this issue, I already discussed on patch[1]
> >> [1] https://lore.kernel.org/lkml/5BEB63C3.1020504@samsung.com/  
> >>
> >> extcon_get_extcon_dev() is used for anywhere except for probe step.
> >> But EPROBE_DEFER is only used on probe step.
> >>
> >> So that it is not clear to return EPROBE_DEFER from extcon_get_extcon_dev()
> >> because extcon_get_extcon_dev() never know either call it on probe function
> >> or not.
> > 
> > Currently extcon_get_extcon_dev() is only called from probe so it's not
> > an issue.
> 
> Even if extcon_get_extcon_dev() is used on probe until now,
> it is possible to use on anywhere as I commented.
> 
> It is difficult to agree this approach without any other solution.
> 
> Basically, the subsystem core never know either probe time or not.
> It means that this issue should be handled in each device driver.
> 

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()?

regards,
dan carpenter