linux-kernel - Re: [PATCH 3/3] extcon: Simplify extcon_dev_register() prototype by removing unnecessary parameter

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Date:	Tue, 3 Sep 2013 08:57:44 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Chanwoo Choi <cw00.choi@...sung.com>
Cc:	linux-kernel@...r.kernel.org, myungjoo.ham@...sung.com,
	kyungmin.park@...sung.com, Graeme Gregory <gg@...mlogic.co.uk>,
	Kishon Vijay Abraham I <kishon@...com>,
	Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>,
	Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH 3/3] extcon: Simplify extcon_dev_register() prototype by
 removing unnecessary parameter

On Mon, Sep 02, 2013 at 10:13:44AM +0900, Chanwoo Choi wrote:
> Hi Greg,
> 
> On 09/02/2013 09:40 AM, Greg KH wrote:
> > On Mon, Sep 02, 2013 at 09:20:08AM +0900, Chanwoo Choi wrote:
> >> This patch remove extcon_dev_register()'s second parameter which means
> >> the pointer of parent device to simplify prototype of this function.
> > 
> > No, please don't.  You want the parent to be passed in, as the core
> > needs it when it is registered with the system, otherwise it will not
> > show up in sysfs properly (i.e. you can't set it afterwards.)
> 
> Currently, each extcon driver have allocated memory for extcon device
> by using devm_kzalloc() in each extcon device driver.

That seems backwards, the extcon core should be the one doing the
allocation, and ownership of the device, like all other subsystem cores
do.  That makes the driver logic much simpler, and the lifetime
ownership correct (i.e. what happens when a device is unbound from a
driver by userspace?  The driver can't control the device memory
anymore...)

thanks,

greg k-h
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