linux-kernel - Re: [PATCH 2/2] iio: dac: cio-dac: Implement and utilize register structures

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Date:   Tue, 14 Jun 2022 12:26:18 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     William Breathitt Gray <william.gray@...aro.org>
Cc:     lars@...afoo.de, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] iio: dac: cio-dac: Implement and utilize register
 structures

On Mon,  6 Jun 2022 10:15:18 -0400
William Breathitt Gray <william.gray@...aro.org> wrote:

> Reduce magic numbers and improve code readability by implementing and
> utilizing named register data structures.
> 
> Signed-off-by: William Breathitt Gray <william.gray@...aro.org>

I'm unconvinced this one really helps readability seeing
as you are only indexing a straight forward array.

Simply using u16 __iomem *
would provide the main cleanup which is avoiding the indexing
via * 2.

Thanks,

Jonathan


> ---
>  drivers/iio/dac/cio-dac.c | 24 ++++++++++++++++--------
>  1 file changed, 16 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/iio/dac/cio-dac.c b/drivers/iio/dac/cio-dac.c
> index 8080984dcb03..7860450ceaf3 100644
> --- a/drivers/iio/dac/cio-dac.c
> +++ b/drivers/iio/dac/cio-dac.c
> @@ -16,6 +16,7 @@
>  #include <linux/isa.h>
>  #include <linux/module.h>
>  #include <linux/moduleparam.h>
> +#include <linux/types.h>
>  
>  #define CIO_DAC_NUM_CHAN 16
>  
> @@ -34,14 +35,22 @@ static unsigned int num_cio_dac;
>  module_param_hw_array(base, uint, ioport, &num_cio_dac, 0);
>  MODULE_PARM_DESC(base, "Measurement Computing CIO-DAC base addresses");
>  
> +/**
> + * struct cio_dac_reg - device register structure
> + * @da:	D/A data
> + */
> +struct cio_dac_reg {
> +	u16 da[CIO_DAC_NUM_CHAN];
> +};
> +
>  /**
>   * struct cio_dac_iio - IIO device private data structure
>   * @chan_out_states:	channels' output states
> - * @base:		base port address of the IIO device
> + * @reg:		I/O address offset for the device registers
>   */
>  struct cio_dac_iio {
>  	int chan_out_states[CIO_DAC_NUM_CHAN];
> -	void __iomem *base;
> +	struct cio_dac_reg __iomem *reg;
>  };
>  
>  static int cio_dac_read_raw(struct iio_dev *indio_dev,
> @@ -61,7 +70,6 @@ static int cio_dac_write_raw(struct iio_dev *indio_dev,
>  	struct iio_chan_spec const *chan, int val, int val2, long mask)
>  {
>  	struct cio_dac_iio *const priv = iio_priv(indio_dev);
> -	const unsigned int chan_addr_offset = 2 * chan->channel;
>  
>  	if (mask != IIO_CHAN_INFO_RAW)
>  		return -EINVAL;
> @@ -71,7 +79,7 @@ static int cio_dac_write_raw(struct iio_dev *indio_dev,
>  		return -EINVAL;
>  
>  	priv->chan_out_states[chan->channel] = val;
> -	iowrite16(val, priv->base + chan_addr_offset);
> +	iowrite16(val, priv->reg->da + chan->channel);
>  
>  	return 0;
>  }
> @@ -106,8 +114,8 @@ static int cio_dac_probe(struct device *dev, unsigned int id)
>  	}
>  
>  	priv = iio_priv(indio_dev);
> -	priv->base = devm_ioport_map(dev, base[id], CIO_DAC_EXTENT);
> -	if (!priv->base)
> +	priv->reg = devm_ioport_map(dev, base[id], CIO_DAC_EXTENT);
> +	if (!priv->reg)
>  		return -ENOMEM;
>  
>  	indio_dev->info = &cio_dac_info;
> @@ -117,8 +125,8 @@ static int cio_dac_probe(struct device *dev, unsigned int id)
>  	indio_dev->name = dev_name(dev);
>  
>  	/* initialize DAC outputs to 0V */
> -	for (i = 0; i < 32; i += 2)
> -		iowrite16(0, priv->base + i);
> +	for (i = 0; i < CIO_DAC_NUM_CHAN; i++)
> +		iowrite16(0, priv->reg->da + i);
>  
>  	return devm_iio_device_register(dev, indio_dev);
>  }