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

On Mon, May 15, 2017 at 11:18:45AM +0200, Quentin Schulz wrote:

Hi Maxime,

On 15/05/2017 11:11, Maxime Ripard wrote:

quoted

On Mon, May 15, 2017 at 09:39:02AM +0200, Quentin Schulz wrote:

quoted

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 <redacted>
Reported-by: Corentin Labbe <clabbe.montjoie@gmail.com>
---

[...]

quoted

quoted

@@ -688,6 +687,12 @@ static int sun4i_gpadc_remove(struct platform_device *pdev)
 
 	pm_runtime_put(&pdev->dev);
 	pm_runtime_disable(&pdev->dev);
+
+	if (pdev->dev.of_node)
+		thermal_zone_of_sensor_unregister(&pdev->dev, info->tzd);
+	else
+		thermal_zone_of_sensor_unregister(pdev->dev.parent, info->tzd);
+

Can't we just store the device used to create the zone in the
structure as well, that would avoid that non-trivial logic.

Yes we could.

I've that same condition in the probe function, if pdev->dev.of_node
then I continue in the probe dedicated to device probed from DT, or I
continue with the probe dedicated to device probed via MFD.

The thermal_zone_of_sensor_register is different in those two functions,
thus, I thought that it would make more sense to replicate the same
condition in the remove to make the relation between the device used in
thermal_zone_of_sensor_register and unregister clear.

That's just a matter of taste for me, so I'm definitely ok to write a v2
for this change.

My point was only a cosmetic one. It's true that you have teh same
condition somewhere else, but you also have a lot of comments to
explain why there, and you don't have them here.

Adding a pointer to the structure would make it trivial for the
reader, without having to duplicate the comments.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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