linux-kernel - Re: [PATCH v3 4/9] iio: adc: mcp3911: use resource-managed version of iio_device

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Message-ID: <20220716182232.5e7da71c@jic23-huawei>
Date:   Sat, 16 Jul 2022 18:22:32 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Marcus Folkesson <marcus.folkesson@...il.com>
Cc:     Kent Gustavsson <kent@...oris.se>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 4/9] iio: adc: mcp3911: use resource-managed version
 of iio_device_register

On Mon,  4 Jul 2022 19:21:11 +0200
Marcus Folkesson <marcus.folkesson@...il.com> wrote:

> Keep using managed resources as much as possible.
> 
> Signed-off-by: Marcus Folkesson <marcus.folkesson@...il.com>
> ---
>  drivers/iio/adc/mcp3911.c | 43 ++++++++++++++++-----------------------
>  1 file changed, 18 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/iio/adc/mcp3911.c b/drivers/iio/adc/mcp3911.c
> index 890af7dca62d..f5fd9da6ab55 100644
> --- a/drivers/iio/adc/mcp3911.c
> +++ b/drivers/iio/adc/mcp3911.c
> @@ -258,6 +258,16 @@ static int mcp3911_config(struct mcp3911 *adc)
>  	return  mcp3911_write(adc, MCP3911_REG_CONFIG, configreg, 2);
>  }
>  
> +static void mcp3911_cleanup(void *_adc)

Very rarely a good idea to cleanup more than one thing in a given
devm_ callback.

> +{
> +	struct mcp3911 *adc = _adc;
> +
> +	if (adc->clki)
> +		clk_disable_unprepare(adc->clki);
> +	if (adc->vref)
> +		regulator_disable(adc->vref);
> +}
> +
>  static int mcp3911_probe(struct spi_device *spi)
>  {
>  	struct iio_dev *indio_dev;
> @@ -271,6 +281,10 @@ static int mcp3911_probe(struct spi_device *spi)
>  	adc = iio_priv(indio_dev);
>  	adc->spi = spi;
>  
> +	ret = devm_add_action_or_reset(&spi->dev, mcp3911_cleanup, adc);
> +	if (ret)
> +		return ret;

You should only register this 'after' what it cleans up.  I want to see
a clear pairing between setup and tear down.

In this particular case register two callbacks, and only register them
if they have anything to do. i.e. the ->clki and ->vref are not null
respectively.

Jonathan


> +
>  	adc->vref = devm_regulator_get_optional(&adc->spi->dev, "vref");
>  	if (IS_ERR(adc->vref)) {
>  		if (PTR_ERR(adc->vref) == -ENODEV) {
> @@ -296,21 +310,20 @@ static int mcp3911_probe(struct spi_device *spi)
>  			dev_err(&adc->spi->dev,
>  				"failed to get adc clk (%ld)\n",
>  				PTR_ERR(adc->clki));
> -			ret = PTR_ERR(adc->clki);
> -			goto reg_disable;
> +			return PTR_ERR(adc->clki);
>  		}
>  	} else {
>  		ret = clk_prepare_enable(adc->clki);
>  		if (ret < 0) {
>  			dev_err(&adc->spi->dev,
>  				"Failed to enable clki: %d\n", ret);
> -			goto reg_disable;
> +			return ret;
>  		}
>  	}
>  
>  	ret = mcp3911_config(adc);
>  	if (ret)
> -		goto clk_disable;
> +		return ret;
>  
>  	indio_dev->name = spi_get_device_id(spi)->name;
>  	indio_dev->modes = INDIO_DIRECT_MODE;
> @@ -322,31 +335,11 @@ static int mcp3911_probe(struct spi_device *spi)
>  
>  	mutex_init(&adc->lock);
>  
> -	ret = iio_device_register(indio_dev);
> -	if (ret)
> -		goto clk_disable;
> -
> -	return ret;
> -
> -clk_disable:
> -	clk_disable_unprepare(adc->clki);
> -reg_disable:
> -	if (adc->vref)
> -		regulator_disable(adc->vref);
> -
> -	return ret;
> +	return devm_iio_device_register(&adc->spi->dev, indio_dev);
>  }
>  
>  static void mcp3911_remove(struct spi_device *spi)
>  {
> -	struct iio_dev *indio_dev = spi_get_drvdata(spi);
> -	struct mcp3911 *adc = iio_priv(indio_dev);
> -
> -	iio_device_unregister(indio_dev);
> -
> -	clk_disable_unprepare(adc->clki);
> -	if (adc->vref)
> -		regulator_disable(adc->vref);
>  }
>  
>  static const struct of_device_id mcp3911_dt_ids[] = {