linux-kernel - Re: [PATCH 5/5] iio: adc: ad7793: use read

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Message-ID: <e4a2757a8eaa148b15111830e4cf783319d0d68b.camel@analog.com>
Date:   Thu, 19 Mar 2020 07:58:22 +0000
From:   "Ardelean, Alexandru" <alexandru.Ardelean@...log.com>
To:     "ardeleanalex@...il.com" <ardeleanalex@...il.com>,
        "lars@...afoo.de" <lars@...afoo.de>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "renatogeh@...il.com" <renatogeh@...il.com>,
        "Hennerich, Michael" <Michael.Hennerich@...log.com>,
        "jic23@...nel.org" <jic23@...nel.org>,
        "Caprioru, Mircea" <Mircea.Caprioru@...log.com>
Subject: Re: [PATCH 5/5] iio: adc: ad7793: use read_avail iio hook for scale
 available

On Wed, 2020-03-18 at 16:10 +0100, Lars-Peter Clausen wrote:
> On 3/18/20 2:40 PM, Alexandru Ardelean wrote:
> > This change uses the read_avail and '.info_mask_shared_by_type_available'
> > modifier to set the available scale.
> > Essentially, nothing changes to the driver's ABI.
> > 
> > The main idea for this patch is to remove the AD7793 driver from
> > checkpatch's radar. There have been about ~3 attempts to fix/break the
> > 'in_voltage-voltage_scale_available' attribute, because checkpatch assumed
> > it to be an arithmetic operation and people were trying to change that.
> 
> Yeah, probably a good idea!
> 
> > Signed-off-by: Alexandru Ardelean <alexandru.ardelean@...log.com>
> > ---
> >   drivers/iio/adc/ad7793.c | 53 +++++++++++++++++++++++++++-------------
> >   1 file changed, 36 insertions(+), 17 deletions(-)
> > 
> > diff --git a/drivers/iio/adc/ad7793.c b/drivers/iio/adc/ad7793.c
> > index 5592ae573e6b..fad98f1801db 100644
> > --- a/drivers/iio/adc/ad7793.c
> > +++ b/drivers/iio/adc/ad7793.c
> > @@ -354,29 +354,28 @@ static IIO_CONST_ATTR_SAMP_FREQ_AVAIL(
> >   static IIO_CONST_ATTR_NAMED(sampling_frequency_available_ad7797,
> >   	sampling_frequency_available, "123 62 50 33 17 16 12 10 8 6 4");
> >   
> > -static ssize_t ad7793_show_scale_available(struct device *dev,
> > -			struct device_attribute *attr, char *buf)
> > +static int ad7793_read_avail(struct iio_dev *indio_dev,
> > +			     struct iio_chan_spec const *chan,
> > +			     const int **vals, int *type, int *length,
> > +			     long mask)
> >   {
> > -	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> >   	struct ad7793_state *st = iio_priv(indio_dev);
> > -	int i, len = 0;
> >   
> > -	for (i = 0; i < ARRAY_SIZE(st->scale_avail); i++)
> > -		len += sprintf(buf + len, "%d.%09u ", st->scale_avail[i][0],
> > -			       st->scale_avail[i][1]);
> > +	switch (mask) {
> > +	case IIO_CHAN_INFO_SCALE:
> > +		*vals = (int *)st->scale_avail;
> 
> Can you change the type of scale_avail to int so we don't need the cast?
> 

So, I don't want to come-up as looking lazy.
[I mean, I am lazy, but I don't want to look lazy.]

I took a look at what it means to change this to a simple array.
The rework feels to me like a bit more noise than is probably worth it.
I mean, if the purpose of the rework is to just get rid of this cast, then it
feels noisy [to me].

That being said, if you insist, I can take a look and do a patch [before this
one] to convert it to a simple array.


> > +		*type = IIO_VAL_INT_PLUS_NANO;
> > +		/* Values are stored in a 2D matrix  */
> > +		*length = ARRAY_SIZE(st->scale_avail) * 2;
> >   
> > -	len += sprintf(buf + len, "\n");
> > +		return IIO_AVAIL_LIST;
> > +	}
> >   
> > -	return len;
> > +	return -EINVAL;
> >   }