Re: [PATCH 1/3] iio: light: vcnl4000: Preserve conf bits when toggle power

[Paul Cercueil <paul@crapouillou.net>]

Hi Mårten,

Le mar., sept. 20 2022 at 20:09:56 +0200, Mårten Lindahl 
<marten.lindahl@axis.com> a écrit :
> As the vcnl4040 and vcnl4200 chip uses runtime power management for
> turning the ambient light and proximity sensors on/off, it overwrites
> the entire register each time. In ALS_CONF register bit fields ALS_IT,
> ALS_PERS, ALS_INT_EN are overwritten. In PS_CONF1 register bit fields
> PS_DUTY, PS_PERS, PS_IT, PS_HD, and PS_INT are overwritten.
> 
> Add functions for preserving the affected bit fields when changing 
> power
> state.
> 
> Signed-off-by: Mårten Lindahl <marten.lindahl@axis.com>
> ---
>  drivers/iio/light/vcnl4000.c | 53 
> ++++++++++++++++++++++++++++++++++--
>  1 file changed, 51 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iio/light/vcnl4000.c 
> b/drivers/iio/light/vcnl4000.c
> index 3db4e26731bb..0b226c684957 100644
> --- a/drivers/iio/light/vcnl4000.c
> +++ b/drivers/iio/light/vcnl4000.c
> @@ -74,6 +74,9 @@
>  #define VCNL4000_PROX_EN	BIT(1) /* start proximity measurement */
>  #define VCNL4000_SELF_TIMED_EN	BIT(0) /* start self-timed 
> measurement */
> 
> +#define VCNL4040_ALS_CONF_ALS_SD	BIT(0) /* Enable ambient light 
> sensor */
> +#define VCNL4040_PS_CONF1_PS_SD	BIT(0) /* Enable proximity sensor */
> +
>  /* Bit masks for interrupt registers. */
>  #define VCNL4010_INT_THR_SEL	BIT(0) /* Select threshold interrupt 
> source */
>  #define VCNL4010_INT_THR_EN	BIT(1) /* Threshold interrupt type */
> @@ -188,16 +191,62 @@ static int vcnl4000_init(struct vcnl4000_data 
> *data)
>  	return data->chip_spec->set_power_state(data, true);
>  };
> 
> +static ssize_t vcnl4000_write_als_enable(struct vcnl4000_data *data, 
> int val)
> +{
> +	int ret;
> +
> +	switch (data->id) {
> +	case VCNL4040:
> +	case VCNL4200:

The switch isn't needed, since vcnl4200_set_power_state() is only 
called for compatible chips.

> +		ret = i2c_smbus_read_word_data(data->client, VCNL4200_AL_CONF);
> +		if (ret < 0)
> +			return ret;
> +
> +		if (val)
> +			ret &= ~VCNL4040_ALS_CONF_ALS_SD;
> +		else
> +			ret |= VCNL4040_ALS_CONF_ALS_SD;
> +
> +		return i2c_smbus_write_word_data(data->client, VCNL4200_AL_CONF,
> +						 ret);

Are you sure a race cannot happen here?

I would assume it cannot, but that's still a bit fishy.

This driver would benefit from a regmap conversion, but it's probably a 
bit too much to ask...

> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static ssize_t vcnl4000_write_ps_enable(struct vcnl4000_data *data, 
> int val)
> +{
> +	int ret;
> +
> +	switch (data->id) {
> +	case VCNL4040:
> +	case VCNL4200:
> +		ret = i2c_smbus_read_word_data(data->client, VCNL4200_PS_CONF1);
> +		if (ret < 0)
> +			return ret;
> +
> +		if (val)
> +			ret &= ~VCNL4040_PS_CONF1_PS_SD;
> +		else
> +			ret |= VCNL4040_PS_CONF1_PS_SD;
> +
> +		return i2c_smbus_write_word_data(data->client,
> +						 VCNL4200_PS_CONF1, ret);
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
>  static int vcnl4200_set_power_state(struct vcnl4000_data *data, bool 
> on)
>  {
>  	u16 val = on ? 0 /* power on */ : 1 /* shut down */;
>  	int ret;
> 
> -	ret = i2c_smbus_write_word_data(data->client, VCNL4200_AL_CONF, 
> val);
> +	ret = vcnl4000_write_als_enable(data, !val);

You set "val" to 0 if "on", and to 1 if "!on", then pass "!val", this 
is very confusing. You could just pass "on" here and below.

Cheers,
-Paul

>  	if (ret < 0)
>  		return ret;
> 
> -	ret = i2c_smbus_write_word_data(data->client, VCNL4200_PS_CONF1, 
> val);
> +	ret = vcnl4000_write_ps_enable(data, !val);
>  	if (ret < 0)
>  		return ret;
> 
> --
> 2.30.2
>