linux-kernel - Re: [PATCHv3 2/9] extcon: Add devm_extcon_dev_allocate/free to manage the resource of extcon device

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Date:	Thu, 24 Apr 2014 10:06:44 -0500
From:	Felipe Balbi <balbi@...com>
To:	Chanwoo Choi <cwchoi00@...il.com>
CC:	Felipe Balbi <balbi@...com>, Chanwoo Choi <cw00.choi@...sung.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	"myungjoo.ham@...sung.com" <myungjoo.ham@...sung.com>,
	<gg@...mlogic.co.uk>, Kishon Vijay Abraham I <kishon@...com>,
	<ckeepax@...nsource.wolfsonmicro.com>,
	Mark Brown <broonie@...nel.org>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Kyungmin Park <kyungmin.park@...sung.com>
Subject: Re: [PATCHv3 2/9] extcon: Add devm_extcon_dev_allocate/free to
 manage the resource of extcon device

Hi,

On Fri, Apr 25, 2014 at 12:03:31AM +0900, Chanwoo Choi wrote:
> On Thu, Apr 24, 2014 at 11:44 PM, Felipe Balbi <balbi@...com> wrote:
> > On Thu, Apr 24, 2014 at 09:34:50PM +0900, Chanwoo Choi wrote:
> >> This patch add device managed devm_extcon_dev_{allocate,free} to automatically
> >> free the memory of extcon_dev structure without handling free operation.
> >>
> >> Signed-off-by: Chanwoo Choi <cw00.choi@...sung.com>
> >> ---
> >>  drivers/extcon/extcon-class.c | 70 +++++++++++++++++++++++++++++++++++--------
> >>  include/linux/extcon.h        | 11 +++++++
> >>  2 files changed, 69 insertions(+), 12 deletions(-)
> >>
> >> diff --git a/drivers/extcon/extcon-class.c b/drivers/extcon/extcon-class.c
> >> index bec66d4..f369168 100644
> >> --- a/drivers/extcon/extcon-class.c
> >> +++ b/drivers/extcon/extcon-class.c
> >> @@ -604,6 +604,64 @@ void extcon_dev_free(struct extcon_dev *edev)
> >>  }
> >>  EXPORT_SYMBOL_GPL(extcon_dev_free);
> >>
> >> +static int devm_extcon_dev_match(struct device *dev, void *res, void *data)
> >> +{
> >> +     struct extcon_dev **r = res;
> >> +
> >> +     if (!r || !*r) {
> >> +             WARN_ON(!r || !*r);
> >> +             return 0;
> >> +     }
> >> +
> >> +     return *r == data;
> >> +}
> >> +
> >> +static void devm_extcon_dev_release(struct device *dev, void *res)
> >> +{
> >> +     extcon_dev_free(*(struct extcon_dev **)res);
> >> +}
> >> +
> >> +/**
> >> + * devm_extcon_dev_allocate - Allocate managed extcon device
> >> + * @dev:             device owning the extcon device being created
> >> + * @supported_cable: Array of supported cable names ending with NULL.
> >> + *                   If supported_cable is NULL, cable name related APIs
> >> + *                   are disabled.
> >> + *
> >> + * This function manages automatically the memory of extcon device using device
> >> + * resource management and simplify the control of freeing the memory of extcon
> >> + * device.
> >> + *
> >> + * Returns the pointer memory of allocated extcon_dev if success or NULL if fail
> >> + */
> >> +struct extcon_dev *devm_extcon_dev_allocate(struct device *dev,
> >> +                                         const char **supported_cable)
> >> +{
> >> +     struct extcon_dev **ptr, *edev;
> >> +
> >> +     ptr = devres_alloc(devm_extcon_dev_release, sizeof(*ptr), GFP_KERNEL);
> >> +     if (!ptr)
> >> +             return NULL;
> >
> > if this fails you return NULL;
> >
> >> +
> >> +     edev = extcon_dev_allocate(supported_cable);
> >
> > if this fails, you return -ENOMEM. Not very nice, if you ask me.
> 
> I'll fix it as following:
> 
> If  both extcon_dev_allocate() and devm_excon_dev_allocate() failed to
> allocate memory,
> two functions would return NULL pointer instead of  ERR_PTR(-ENOMEM).

your call, I'd rather see them both returning ERR_PTR(-ENOMEM), but no
strong feelings.

cheers

-- 
balbi

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