linux-kernel - Re: [PATCH v3 2/2] iio: adc: Add TI ADS1100 and ADS1000

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Date:   Thu, 2 Mar 2023 05:16:54 -0800
From:   Lars-Peter Clausen <lars@...afoo.de>
To:     Mike Looijmans <mike.looijmans@...ic.nl>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     devicetree@...r.kernel.org, linux-iio@...r.kernel.org,
        Caleb Connolly <caleb.connolly@...aro.org>,
        ChiYuan Huang <cy_huang@...htek.com>,
        ChiaEn Wu <chiaen_wu@...htek.com>,
        Cosmin Tanislav <demonsingur@...il.com>,
        Ibrahim Tilki <Ibrahim.Tilki@...log.com>,
        Jonathan Cameron <jic23@...nel.org>,
        Ramona Bolboaca <ramona.bolboaca@...log.com>,
        William Breathitt Gray <william.gray@...aro.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/2] iio: adc: Add TI ADS1100 and ADS1000

On 3/1/23 23:49, Mike Looijmans wrote:
>
>
>> ...
>> ...
>>
>>> +static int ads1100_runtime_suspend(struct device *dev)
>>> +{
>>> +    struct iio_dev *indio_dev = 
>>> i2c_get_clientdata(to_i2c_client(dev));
>>> +    struct ads1100_data *data = iio_priv(indio_dev);
>>> +
>>> +    ads1100_set_config_bits(data, ADS1100_CFG_SC, ADS1100_SINGLESHOT);
>>> +    regulator_disable(data->reg_vdd);
>> Wrong devm / non-devm ordering.
>
> Don't understand your remark, can you explain further please?
>
> devm / non-devm ordering would be related to the "probe" function. As 
> far as I can tell, I'm not allocating resources after the devm calls. 
> And the "remove" is empty.

Strictly speaking we need to unregister the IIO device before disabling 
the regulator, otherwise there is a small window where the IIO device 
still exists, but doesn't work anymore. This is a very theoretical 
scenario though.

You are lucky :) There is a new function 
`devm_regulator_get_enable()`[1], which will manage the 
regulator_disable() for you. Using that will also reduce the boilerplate 
in `probe()` a bit

- Lars

[1] https://lwn.net/Articles/904383/