linux-kernel - Re: [PATCH v2] staging: bcm2835-audio: Release resources on module

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Message-ID: <CAHp75Vfwpwcc6_somOcSMYwmBhnkSwR7vn2piAZwA1GFkGAJRw@mail.gmail.com>
Date:   Wed, 21 Mar 2018 17:03:21 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Kirill Marinushkin <k.marinushkin@...il.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Eric Anholt <eric@...olt.net>,
        Stefan Wahren <stefan.wahren@...e.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        bcm-kernel-feedback-list <bcm-kernel-feedback-list@...adcom.com>,
        Michael Zoran <mzoran@...wfest.net>,
        linux-rpi-kernel@...ts.infradead.org,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        devel@...verdev.osuosl.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] staging: bcm2835-audio: Release resources on module_exit()

On Thu, Mar 15, 2018 at 7:57 AM, Kirill Marinushkin
<k.marinushkin@...il.com> wrote:
> On 03/13/18 22:23, Andy Shevchenko wrote:
>> On Tue, Mar 13, 2018 at 9:34 PM, Kirill Marinushkin
>> <k.marinushkin@...il.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.

Please, remove.
If you don't know, perhaps you need to spend more time on doing homework?

% git grep -n -w dev_set_drvdata -- drivers/base/dd.c
drivers/base/dd.c:469:          dev_set_drvdata(dev, NULL);
drivers/base/dd.c:499:  dev_set_drvdata(dev, NULL);
drivers/base/dd.c:902:          dev_set_drvdata(dev, NULL);

Last one is the point of your interest.

-- 
With Best Regards,
Andy Shevchenko