Re: [PATCH v2 08/14] iio: accel: adxl345: add freefall feature

[Jonathan Cameron <jic23@kernel.org>]

On Mon, 10 Feb 2025 11:01:13 +0000
Lothar Rubusch <l.rubusch@gmail.com> wrote:

> Add the freefall detection of the sensor together with a threshold and
> time parameter. A freefall event is detected if the measuring signal
> falls below the threshold.
> 
> Signed-off-by: Lothar Rubusch <l.rubusch@gmail.com>
Hi Lothar,

A few follow on comments from earlier suggestions.

Jonathan

> ---
>  drivers/iio/accel/adxl345_core.c | 118 +++++++++++++++++++++++++++++++
>  1 file changed, 118 insertions(+)
> 
> diff --git a/drivers/iio/accel/adxl345_core.c b/drivers/iio/accel/adxl345_core.c
> index b6966fee3e3d..56c5a4d85d71 100644
> --- a/drivers/iio/accel/adxl345_core.c
> +++ b/drivers/iio/accel/adxl345_core.c
> @@ -84,6 +84,9 @@ struct adxl345_state {
>  	u32 tap_window_us;
>  	bool tap_suppressed;
>  
> +	u8 ff_threshold;
> +	u32 ff_time_ms;
> +
>  	__le16 fifo_buf[ADXL345_DIRS * ADXL345_FIFO_SIZE + 1] __aligned(IIO_DMA_MINALIGN);
>  };
>  
> @@ -104,6 +107,14 @@ static struct iio_event_spec adxl345_events[] = {
>  			BIT(IIO_EV_INFO_RESET_TIMEOUT) |
>  			BIT(IIO_EV_INFO_TAP2_MIN_DELAY),
>  	},
> +	{
> +		/* free fall */
> +		.type = IIO_EV_TYPE_MAG,
> +		.dir = IIO_EV_DIR_FALLING,
> +		.mask_shared_by_type = BIT(IIO_EV_INFO_ENABLE) |
> +			BIT(IIO_EV_INFO_VALUE) |
> +			BIT(IIO_EV_INFO_PERIOD),
> +	},
>  };
>  
>  #define ADXL345_CHANNEL(index, reg, axis) {					\
> @@ -354,6 +365,68 @@ static int adxl345_set_tap_latent(struct adxl345_state *st, u32 val_int,
>  	return _adxl345_set_tap_time(st, ADXL345_TAP_TIME_LATENT, val_fract_us);
>  }
>  
> +/* ff */

Spell it out.  Otherwise this comment doesn't add anything given function
names all include ff.

> +
> +static int adxl345_is_ff_en(struct adxl345_state *st, bool *en)
> +{
> +	int ret;
> +	unsigned int regval;
> +
> +	ret = regmap_read(st->regmap, ADXL345_REG_INT_ENABLE, &regval);

Why read into regval then use intmap?
I would just use regval.

> +	if (ret)
> +		return ret;
> +
> +	*en = FIELD_GET(ADXL345_INT_FREE_FALL, st->int_map) > 0;

It's a single bit isn't it?  In which case just set to that value
which will be 1 or 0 anyway.

I'm not sure this function adds enough to be worth keeping.
Maybe just do the regmap_read() and FIELD_GET at the call site.

> +
> +	return 0;
> +}
> +
> +static int adxl345_set_ff_en(struct adxl345_state *st, bool cmd_en)
> +{
> +	bool en = cmd_en && st->ff_threshold > 0 && st->ff_time_ms > 0;
> +
> +	en ? __set_bit(ilog2(ADXL345_INT_FREE_FALL), (unsigned long *)&st->int_map)
> +		: __clear_bit(ilog2(ADXL345_INT_FREE_FALL), (unsigned long *)&st->int_map);
> +
> +	return regmap_write(st->regmap, ADXL345_REG_INT_ENABLE, st->int_map);

As before, if we just use the regmap cache can use the regmap functions
for clearing and setting bits.

> +}
> +
>