linux-kernel - Re: [PATCHv3 1/9] extcon: Add extcon_dev_allocate/free() to control the memory of extcon device

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Message-ID: <CAGTfZH0+VCvr=JNbq8kbtC2CDN63k28+oSd__6sb+Qy2tQ4_ng@mail.gmail.com>
Date:	Thu, 24 Apr 2014 23:58:29 +0900
From:	Chanwoo Choi <cwchoi00@...il.com>
To:	Felipe Balbi <balbi@...com>
Cc:	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 1/9] extcon: Add extcon_dev_allocate/free() to control
 the memory of extcon device

Hi,

On Thu, Apr 24, 2014 at 11:42 PM, Felipe Balbi <balbi@...com> wrote:
> On Thu, Apr 24, 2014 at 09:34:49PM +0900, Chanwoo Choi wrote:
>> This patch add APIs to control the extcon device on extcon provider driver.
>> The extcon_dev_allocate() allocates the memory of extcon device and initializes
>> supported cables. And then extcon_dev_free() decrement the reference of the
>> device of extcon device and free the memory of the extcon device. This APIs
>> must need to implement devm_extcon_dev_allocate()/free() APIs.
>>
>> Signed-off-by: Chanwoo Choi <cw00.choi@...sung.com>
>> ---
>>  drivers/extcon/extcon-class.c | 39 +++++++++++++++++++++++++++++++++++++++
>>  include/linux/extcon.h        | 13 +++++++++++++
>>  2 files changed, 52 insertions(+)
>>
>> diff --git a/drivers/extcon/extcon-class.c b/drivers/extcon/extcon-class.c
>> index f6df689..bec66d4 100644
>> --- a/drivers/extcon/extcon-class.c
>> +++ b/drivers/extcon/extcon-class.c
>> @@ -565,6 +565,45 @@ static void dummy_sysfs_dev_release(struct device *dev)
>>  {
>>  }
>>
>> +/*
>> + * extcon_dev_allocate() - Allocate the memory of extcon device.
>> + * @supported_cable: Array of supported cable names ending with NULL.
>> + *                   If supported_cable is NULL, cable name related APIs
>> + *                   are disabled.
>> + *
>> + * This function allocates the memory for extcon device without allocating
>> + * memory in each extcon provider driver and initialize default setting for
>> + * extcon device.
>> + *
>> + * Return the pointer of extcon device if success or ERR_PTR(err) if fail
>> + */
>> +struct extcon_dev *extcon_dev_allocate(const char **supported_cable)
>> +{
>> +     struct extcon_dev *edev;
>> +
>> +     edev = kzalloc(sizeof(*edev), GFP_KERNEL);
>> +     if (!edev) {
>> +             pr_err("Failed to allocate the memory for extcon device\n");
>> +             return ERR_PTR(-ENOMEM);
>> +     }
>> +
>> +     edev->max_supported = 0;
>> +     edev->supported_cable = supported_cable;
>> +
>> +     return edev;
>> +}
>> +
>> +/*
>> + * extcon_dev_free() - Free the memory of extcon device.
>> + * @edev:    the extcon device to free
>> + */
>> +void extcon_dev_free(struct extcon_dev *edev)
>> +{
>> +     if (edev)
>> +             kfree(edev);
>
> kfree(NULL) is safe

I don't understand about meaning 'kfree(NULL)'.
Why do I free 'NULL' pointer' instead of 'edev' pointer?
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