linux-kernel - Re: [PATCH v2] iio: adc: sun4i-gpadc-iio: fix parent device being used in devm function

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Message-ID: <52a7fb4c-af4f-d9d1-4ed9-906a08eb41b3@kernel.org>
Date:   Sun, 21 May 2017 15:18:14 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Maxime Ripard <maxime.ripard@...e-electrons.com>,
        Quentin Schulz <quentin.schulz@...e-electrons.com>
Cc:     knaack.h@....de, lars@...afoo.de, pmeerw@...erw.net, wens@...e.org,
        clabbe.montjoie@...il.com, linux-iio@...r.kernel.org,
        thomas.petazzoni@...e-electrons.com, linux-sunxi@...glegroups.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] iio: adc: sun4i-gpadc-iio: fix parent device being
 used in devm function

On 18/05/17 07:51, Maxime Ripard wrote:
> On Thu, May 18, 2017 at 08:36:07AM +0200, Quentin Schulz wrote:
>> For the sake of DT binding stability, this IIO driver is a child of an
>> MFD driver for Allwinner A10, A13 and A31 because there already exists a
>> DT binding for this IP. The MFD driver has a DT node but the IIO driver
>> does not.
>>
>> The IIO device registers the temperature sensor in the thermal framework
>> using the DT node of the parent, the MFD device, so the thermal
>> framework could match the phandle to the MFD device in the DT and the
>> struct device used to register in the thermal framework.
>>
>> devm_thermal_zone_of_sensor_register was previously used to register the
>> thermal sensor with the parent struct device of the IIO device,
>> representing the MFD device. By doing so, we registered actually the
>> parent in the devm routine and not the actual IIO device.
>>
>> This lead to the devm unregister function not being called when the IIO
>> module driver is removed. It resulted in the thermal framework still
>> polling the get_temp function of the IIO module while the device doesn't
>> exist anymore, thus generated a kernel panic.
>>
>> Use the non-devm function instead and do the unregister manually in the
>> remove function.
>>
>> Fixes: d1caa9905538 ("iio: adc: add support for Allwinner SoCs ADC")
>>
>> Signed-off-by: Quentin Schulz <quentin.schulz@...e-electrons.com>
>> Reported-by: Corentin Labbe <clabbe.montjoie@...il.com>
> 
> Reviewed-by: Maxime Ripard <maxime.ripard@...e-electrons.com>
> 
> Maxime
> 
Thanks to all involved with tracking this one down.

Jonathan