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

[Chanwoo Choi]

Hi,

On Thu, Apr 24, 2014 at 11:42 PM, Felipe Balbi <balbi@xxxxxx> 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@xxxxxxxxxxx>
>> ---
>>  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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