linux-kernel - Re: [PATCH] iio: adc: mcp320x: Simplify device removal logic

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Message-ID: <20240210155857.59c58dcc@jic23-huawei>
Date: Sat, 10 Feb 2024 15:58:57 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: Arturas Moskvinas <arturas.moskvinas@...il.com>
Cc: Jonathan.Cameron@...wei.com, oskar.andero@...il.com, lars@...afoo.de,
 lukas@...ner.de, linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: adc: mcp320x: Simplify device removal logic

On Thu,  8 Feb 2024 11:43:39 +0200
Arturas Moskvinas <arturas.moskvinas@...il.com> wrote:

> Use devm_* APIs to enable regulator and to register in IIO infrastructure.
> 
> Signed-off-by: Arturas Moskvinas <arturas.moskvinas@...il.com>

Don't get the same regulator twice so as automate turning it off.
The devm_regulator_get_enable() call is carefully hiding the
regulator for cases where the driver never accesses it.

Here we need it to read the voltage.

To convert such a case to fully devm managed, use a
devm_add_action_or_reset() and a custom callback.

> ---
>  drivers/iio/adc/mcp320x.c | 19 ++-----------------
>  1 file changed, 2 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/iio/adc/mcp320x.c b/drivers/iio/adc/mcp320x.c
> index f3b81798b3c9..4685eed35271 100644
> --- a/drivers/iio/adc/mcp320x.c
> +++ b/drivers/iio/adc/mcp320x.c
> @@ -388,7 +388,6 @@ static int mcp320x_probe(struct spi_device *spi)
>  	indio_dev->name = spi_get_device_id(spi)->name;
>  	indio_dev->modes = INDIO_DIRECT_MODE;
>  	indio_dev->info = &mcp320x_info;
> -	spi_set_drvdata(spi, indio_dev);
>  
>  	device_index = spi_get_device_id(spi)->driver_data;
>  	chip_info = &mcp320x_chip_infos[device_index];
> @@ -441,31 +440,17 @@ static int mcp320x_probe(struct spi_device *spi)
>  	if (IS_ERR(adc->reg))
>  		return PTR_ERR(adc->reg);

Just above here is the first regulator get. Whilst it may work
we should not get it twice as the logic gets confused at the very least.


>  
> -	ret = regulator_enable(adc->reg);
> +	ret = devm_regulator_get_enable(&spi->dev, "vref");
>  	if (ret < 0)
>  		return ret;
>  
>  	mutex_init(&adc->lock);
>  
> -	ret = iio_device_register(indio_dev);
> -	if (ret < 0)
> -		goto reg_disable;
> -
> -	return 0;
> -
> -reg_disable:
> -	regulator_disable(adc->reg);
> -
> -	return ret;
> +	return devm_iio_device_register(&spi->dev, indio_dev);
>  }
>  
>  static void mcp320x_remove(struct spi_device *spi)
>  {
> -	struct iio_dev *indio_dev = spi_get_drvdata(spi);
> -	struct mcp320x *adc = iio_priv(indio_dev);
> -
> -	iio_device_unregister(indio_dev);
> -	regulator_disable(adc->reg);
>  }
Had the change otherwise been ok...

You should be able to remove this function completely now it is empty.
https://elixir.bootlin.com/linux/latest/source/drivers/spi/spi.c#L446
checks it's existence before calling it.

Thanks

Jonathan

>  
>  static const struct of_device_id mcp320x_dt_ids[] = {
> 
> base-commit: 047371968ffc470769f541d6933e262dc7085456