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

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Date:   Thu, 2 Mar 2023 16:24:06 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Lars-Peter Clausen <lars@...afoo.de>
Cc:     Mike Looijmans <mike.looijmans@...ic.nl>,
        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 Thu, Mar 02, 2023 at 05:20:38AM -0800, Lars-Peter Clausen wrote:
> On 3/2/23 05:16, Lars-Peter Clausen wrote:
> > 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
> > 
> > [1] https://lwn.net/Articles/904383/
> > 
> Sorry, just saw that Andy's comment was on the suspend() function, not
> remove(). In that case there is of course no need for any devm things. But
> still a good idea to use `devm_regulator_get_enable()` in probe for the
> boiler plate.

Yeah, sorry, I mistakenly took it as ->remove().

-- 
With Best Regards,
Andy Shevchenko