linux-kernel - Re: [PATCH 2/2] iio: light: vcnl4000: Add ps high definition for vcnl4040

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Date: Sun, 17 Dec 2023 14:15:54 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: Mårten Lindahl <marten.lindahl@...s.com>
Cc: Lars-Peter Clausen <lars@...afoo.de>, <linux-iio@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>, <kernel@...s.com>
Subject: Re: [PATCH 2/2] iio: light: vcnl4000: Add ps high definition for
 vcnl4040

On Fri, 15 Dec 2023 13:43:05 +0100
Mårten Lindahl <marten.lindahl@...s.com> wrote:

> The vcnl4040 proximity sensor defaults to 12 bit data resolution, but
> the chip also supports 16 bit data resolution, which is called proximity
> high definition (PS_HD).
> 
> Add read/write attribute for proximity resolution, and read attribute
> for available proximity resolution values for the vcnl4040 chip.
> 
> Signed-off-by: Mårten Lindahl <marten.lindahl@...s.com>
I'll review this on basis the usecase is clear (see reply to cover letter)

The manipulation of the CONF1 and CONF2 registers in a pair is rather odd given you
only want to change one bit here.

Why is that done?
> ---
>  drivers/iio/light/vcnl4000.c | 87 +++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 85 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iio/light/vcnl4000.c b/drivers/iio/light/vcnl4000.c
> index fdf763a04b0b..2addff635b79 100644
> --- a/drivers/iio/light/vcnl4000.c
> +++ b/drivers/iio/light/vcnl4000.c
> @@ -90,6 +90,7 @@
>  #define VCNL4040_PS_CONF1_PS_SHUTDOWN	BIT(0)
>  #define VCNL4040_PS_CONF2_PS_IT	GENMASK(3, 1) /* Proximity integration time */
>  #define VCNL4040_CONF1_PS_PERS	GENMASK(5, 4) /* Proximity interrupt persistence setting */
> +#define VCNL4040_PS_CONF2_PS_HD		BIT(11)	/* Proximity high definition */
>  #define VCNL4040_PS_CONF2_PS_INT	GENMASK(9, 8) /* Proximity interrupt mode */
>  #define VCNL4040_PS_CONF3_MPS		GENMASK(6, 5) /* Proximity multi pulse number */
>  #define VCNL4040_PS_MS_LED_I		GENMASK(10, 8) /* Proximity current */
> @@ -170,6 +171,11 @@ static const int vcnl4040_ps_calibbias_ua[][2] = {
>  	{0, 200000},
>  };
>  
> +static const int vcnl4040_ps_resolutions[2] = {
> +	12,
> +	16
> +};
> +
>  static const int vcnl4040_als_persistence[] = {1, 2, 4, 8};
>  static const int vcnl4040_ps_persistence[] = {1, 2, 3, 4};
>  static const int vcnl4040_ps_oversampling_ratio[] = {1, 2, 4, 8};
> @@ -880,6 +886,54 @@ static ssize_t vcnl4040_write_ps_calibbias(struct vcnl4000_data *data, int val)
>  	return ret;
>  }
>  
> +static ssize_t vcnl4040_read_ps_resolution(struct vcnl4000_data *data, int *val, int *val2)
> +{
> +	int ret;
> +
> +	ret = i2c_smbus_read_word_data(data->client, VCNL4200_PS_CONF1);
The field seems to be in PS_CONF2.  So you are reading a word and I guess that
gets you two registers.  Can we not do a byte read to get just CONF2?
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = FIELD_GET(VCNL4040_PS_CONF2_PS_HD, ret);
> +	if (ret >= ARRAY_SIZE(vcnl4040_ps_resolutions))
> +		return -EINVAL;
> +
> +	*val = vcnl4040_ps_resolutions[ret];
> +	*val2 = 0;
> +
> +	return ret;
> +}
> +
> +static ssize_t vcnl4040_write_ps_resolution(struct vcnl4000_data *data, int val)
> +{
> +	unsigned int i;
> +	int ret;
> +	u16 regval;
> +
> +	for (i = 0; i < ARRAY_SIZE(vcnl4040_ps_resolutions); i++) {
> +		if (val == vcnl4040_ps_resolutions[i])
> +			break;
> +	}
> +
> +	if (i >= ARRAY_SIZE(vcnl4040_ps_resolutions))
> +		return -EINVAL;
> +
> +	mutex_lock(&data->vcnl4000_lock);
> +
> +	ret = i2c_smbus_read_word_data(data->client, VCNL4200_PS_CONF1);
> +	if (ret < 0)
> +		goto out_unlock;
> +
> +	regval = (ret & ~VCNL4040_PS_CONF2_PS_HD);
> +	regval |= FIELD_PREP(VCNL4040_PS_CONF2_PS_HD, i);
> +	ret = i2c_smbus_write_word_data(data->client, VCNL4200_PS_CONF1,
> +					regval);
> +
> +out_unlock:
> +	mutex_unlock(&data->vcnl4000_lock);
> +	return ret;
> +}
c),
>