linux-kernel - Re: [PATCH v3 6/6] iio:adxl372: Add filter bandwidth support

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Date:   Fri, 3 Aug 2018 22:32:33 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Stefan Popa <stefan.popa@...log.com>
Cc:     <broonie@...nel.org>, <lars@...afoo.de>,
        <Michael.Hennerich@...log.com>, <knaack.h@....de>,
        <pmeerw@...erw.net>, <mark.rutland@....com>, <davem@...emloft.net>,
        <mchehab+samsung@...nel.org>, <gregkh@...uxfoundation.org>,
        <akpm@...ux-foundation.org>, <robh+dt@...nel.org>,
        <linux-iio@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 6/6] iio:adxl372: Add filter bandwidth support

On Fri, 3 Aug 2018 16:02:21 +0300
Stefan Popa <stefan.popa@...log.com> wrote:

> This patch adds the option for the user to select the filter bandwidth. The
> user can also read the available bandwidths which are always adjusted to be
> at most half of the sampling frequency. Furthermore, the currently selected
> bandwidth can be read via the read_raw function, while the write_raw sets a
> new bandwidth value.
> 
> Signed-off-by: Stefan Popa <stefan.popa@...log.com>
Another good one.  Same comment as previous :)

Jonathan

> ---
>  drivers/iio/accel/adxl372.c | 38 ++++++++++++++++++++++++++++++++++++--
>  1 file changed, 36 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iio/accel/adxl372.c b/drivers/iio/accel/adxl372.c
> index 80b1838..3a9d55a 100644
> --- a/drivers/iio/accel/adxl372.c
> +++ b/drivers/iio/accel/adxl372.c
> @@ -196,6 +196,10 @@ static const int adxl372_samp_freq_tbl[5] = {
>  	400, 800, 1600, 3200, 6400,
>  };
>  
> +static const int adxl372_bw_freq_tbl[5] = {
> +	200, 400, 800, 1600, 3200,
> +};
> +
>  struct adxl372_axis_lookup {
>  	unsigned int bits;
>  	enum adxl372_fifo_format fifo_format;
> @@ -218,7 +222,8 @@ static const struct adxl372_axis_lookup adxl372_axis_lookup_table[] = {
>  	.channel2 = IIO_MOD_##axis,					\
>  	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),			\
>  	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) |		\
> -				    BIT(IIO_CHAN_INFO_SAMP_FREQ),	\
> +				    BIT(IIO_CHAN_INFO_SAMP_FREQ) |	\
> +		BIT(IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY),	\
>  	.scan_index = index,						\
>  	.scan_type = {							\
>  		.sign = 's',						\
> @@ -656,6 +661,9 @@ static int adxl372_read_raw(struct iio_dev *indio_dev,
>  	case IIO_CHAN_INFO_SAMP_FREQ:
>  		*val = adxl372_samp_freq_tbl[st->odr];
>  		return IIO_VAL_INT;
> +	case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY:
> +		*val = adxl372_bw_freq_tbl[st->bw];
> +		return IIO_VAL_INT;
>  	}
>  
>  	return -EINVAL;
> @@ -666,7 +674,7 @@ static int adxl372_write_raw(struct iio_dev *indio_dev,
>  			     int val, int val2, long info)
>  {
>  	struct adxl372_state *st = iio_priv(indio_dev);
> -	int odr_index, ret;
> +	int odr_index, bw_index, ret;
>  
>  	switch (info) {
>  	case IIO_CHAN_INFO_SAMP_FREQ:
> @@ -698,11 +706,34 @@ static int adxl372_write_raw(struct iio_dev *indio_dev,
>  			ret = adxl372_set_bandwidth(st, odr_index);
>  
>  		return ret;
> +	case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY:
> +		bw_index = adxl372_find_closest_match(adxl372_bw_freq_tbl,
> +					ARRAY_SIZE(adxl372_bw_freq_tbl),
> +					val);
> +		return adxl372_set_bandwidth(st, bw_index);
>  	default:
>  		return -EINVAL;
>  	}
>  }
>  
> +static ssize_t adxl372_show_filter_freq_avail(struct device *dev,
> +					      struct device_attribute *attr,
> +					      char *buf)
> +{
> +	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> +	struct adxl372_state *st = iio_priv(indio_dev);
> +	int i;
> +	size_t len = 0;
> +
> +	for (i = 0; i <= st->odr; i++)
> +		len += scnprintf(buf + len, PAGE_SIZE - len,
> +				 "%d ", adxl372_bw_freq_tbl[i]);
> +
> +	buf[len - 1] = '\n';
> +
> +	return len;
> +}
> +
>  static ssize_t adxl372_get_fifo_enabled(struct device *dev,
>  					  struct device_attribute *attr,
>  					  char *buf)
> @@ -826,9 +857,12 @@ static const struct iio_trigger_ops adxl372_trigger_ops = {
>  };
>  
>  static IIO_CONST_ATTR_SAMP_FREQ_AVAIL("400 800 1600 3200 6400");
> +static IIO_DEVICE_ATTR(in_accel_filter_low_pass_3db_frequency_available,
> +		       0444, adxl372_show_filter_freq_avail, NULL, 0);
>  
>  static struct attribute *adxl372_attributes[] = {
>  	&iio_const_attr_sampling_frequency_available.dev_attr.attr,
> +	&iio_dev_attr_in_accel_filter_low_pass_3db_frequency_available.dev_attr.attr,
>  	NULL,
>  };
>