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

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Date:   Tue, 14 Jun 2022 12:15:40 -0400
From:   William Breathitt Gray <william.gray@...aro.org>
To:     Jonathan Cameron <jic23@...nel.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 Tue, Jun 14, 2022 at 12:26:18PM +0100, Jonathan Cameron wrote:
> 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

I agree, that is a much simpler approach and reduces the changes we need
to make to this file. I'll adjust this to u16 __iomem * in v2.

William Breathitt Gray

> 
> 
> > ---
> >  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);
> >  }
> 

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