From mboxrd@z Thu Jan  1 00:00:00 1970
From: k.marinushkin@gmail.com (Kirill Marinushkin)
Date: Thu, 15 Mar 2018 06:57:21 +0100
Subject: [PATCH v2] staging: bcm2835-audio: Release resources on
 module_exit()
In-Reply-To: <CAHp75Ve9MRAgSu74Mzr2defd84umyeKpfvX51-Qhk4SvLx3Qng@mail.gmail.com>
References: <63ee611d-9fd7-a67a-45aa-229cc4a83ed2@gmail.com>
 <20180313193414.11535-1-k.marinushkin@gmail.com>
 <CAHp75Ve9MRAgSu74Mzr2defd84umyeKpfvX51-Qhk4SvLx3Qng@mail.gmail.com>
Message-ID: <1a59a938-0381-49f4-dfd9-c7a52bdb0eae@gmail.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On 03/13/18 22:23, Andy Shevchenko wrote:
> On Tue, Mar 13, 2018 at 9:34 PM, Kirill Marinushkin
> <k.marinushkin@gmail.com> wrote:
>> In the current implementation, `rmmod snd_bcm2835` does not release
>> resources properly. It causes an oops when trying to list sound devices.
>>
>> This commit fixes it.
> Nice catch!
>
> See my comments below.
>
>>  static void snd_devm_unregister_child(struct device *dev, void *res)
>>  {
>>         struct device *childdev = *(struct device **)res;
>> +       struct bcm2835_chip *chip = dev_get_drvdata(childdev);
>> +       struct snd_card *card = chip->card;
>> +
>> +       snd_card_free(card);
>> +       dev_set_drvdata(childdev, NULL);
> AFAIU this is done by device core.

Maybe you are right. But I don't know, which function in the device core does it.
It is safe to have this line. So, I suggest to keep it.

>
>>         device_unregister(childdev);
>>  }
>> +static void snd_devm_release(struct device *dev)
>> +{
>> +       struct bcm2835_chip *chip = dev_get_drvdata(dev);
>> +
>> +       kfree(chip);
>> +}
>
>>  /* chip-specific constructor
>> @@ -122,7 +136,7 @@ static int snd_bcm2835_create(struct snd_card *card,
>>
>>         err = snd_device_new(card, SNDRV_DEV_LOWLEVEL, chip, &ops);
>>         if (err) {
>> -               snd_bcm2835_free(chip);
>> +               kfree(chip);
> Do you call device_register() inside snd_device_new()?
> In this case you might need put_device() here instead of simple kfree().

No, from what I see, device_register() does not happen inside snd_device_new().

>>                 return err;
>>         }