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 18:16:40 -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 Wed, Sep 04, 2013 at 09:17:02AM +0900, Chanwoo Choi wrote:
> On 09/04/2013 12:57 AM, Greg KH wrote:
> > 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...)
> > 
> 
> OK,
> The extcon core will control memory allocation instead of extcon device driver
> as following.
> - devm_extcon_allocate_device(struct device *dev)

Huh?  Why do you need a devm allocator?  This is a "real" child device,
just create it with a "extcon_create_device()" or some such call, like
all other busses do?

thanks,

greg k-h
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