Subject: Re: [PATCH v7 2/4] power: reset: add reboot mode driver
To: Andy Yan <andy.yan@rock-chips.com>, robh+dt@kernel.org, sre@kernel.org,
        heiko@sntech.de, john.stultz@linaro.org, arnd@arndb.de
References: <1459304304-9713-1-git-send-email-andy.yan@rock-chips.com>
 <1459304443-9811-1-git-send-email-andy.yan@rock-chips.com>
 <56FB49B3.2040505@samsung.com> <57045D6B.2080907@rock-chips.com>
Cc: mark.rutland@arm.com, catalin.marinas@arm.com, will.deacon@arm.com,
        alexandre.belloni@free-electrons.com, f.fainelli@gmail.com,
        linux@arm.linux.org.uk, dbaryshkov@gmail.com, linux-pm@vger.kernel.org,
        linux-rockchip@lists.infradead.org, wxt@rock-chips.com,
        devicetree@vger.kernel.org, pawel.moll@arm.com,
        ijc+devicetree@hellion.org.uk, lorenzo.pieralisi@arm.com,
        matthias.bgg@gmail.com, linux-arm-kernel@lists.infradead.org,
        moritz.fischer@ettus.com, mbrugger@suse.com,
        linux-kernel@vger.kernel.org, galak@codeaurora.org, olof@lixom.net,
        jun.nie@linaro.org, dwmw2@infradead.org
From: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Message-id: <57045F9D.1000502@samsung.com>
Date: Wed, 06 Apr 2016 10:00:13 +0900
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On 06.04.2016 09:50, Andy Yan wrote:

(...)

>>> +            return -ENOMEM;
>>> +
>>> +        info->mode = kstrdup_const(prop->name + len, GFP_KERNEL);
>>> +        if (of_property_read_u32(np, prop->name, &info->magic)) {
>>> +            dev_err(dev, "reboot mode %s without magic number\n",
>>> +                info->mode);
>>> +            devm_kfree(dev, info);
>>> +            continue;
>>> +        }
>>> +        list_add_tail(&info->list, &reboot->head);
>>> +    }
>>> +    of_node_put(np);
>> If you of_node_put() here, there is no sense in getting it before. I
>> mentioned of_node_get() only because I am not sure about life-cycle of
>> nodes in case of DT overlays and you are storing the pointer to string
>> from DT.
>>
>> The doubts I have are concerning only the case of freeing nodes from
>> overlay.
>>
>> I don't know if of_node_get() is needed but of_node_get()+of_node_put()
>> seems useless.
> 
> 
>  I am also not sure about it. Maybe just drop of_node_get/put ?

OK, let's drop both get() and put().

(...)

>>> +
>>> +static const struct of_device_id syscon_reboot_mode_of_match[] = {
>>> +    { .compatible = "syscon-reboot-mode" },
>>> +    {}
>>> +};
>>> +
>>> +static struct platform_driver syscon_reboot_mode_driver = {
>>> +    .probe = syscon_reboot_mode_probe,
>> Cleanup needed. What will happen after device unbind? Memory will be
>> released (devm-*()) but reboot notifier won't thus leading to OOPS on
>> reboot.
> 
>     From the kernel_restart_prepare function, the reboot notifier will
> be called before device_shutdown. Is there any other case the device
> unbind before reboot notifier
> called?

This is a regular module platform driver so unbind can happen any time
initiated by user, either by unbind command or by module removal. User
can then re-bind device or not - probably does not matter. Anyway after
such first unbind, the restart will kaboom instead of do a restart.

Beside that, you always should clean up, regardless of restart or not.
If you do not want unbind (thus no need of cleanup) then forbid it by
making it a non-module with suppressed bind.

Best regards,
Krzysztof