Re: [PATCH v1 08/12] iio: accel: adxl345: add double tap feature

[Jonathan Cameron <jic23@kernel.org>]

On Tue, 28 Jan 2025 12:00:56 +0000
Lothar Rubusch <l.rubusch@gmail.com> wrote:

> Add the double tap feature of the sensor. The interrupt handler needs
> to catch and forwared the event to the IIO channel. The single tap
> implementation now is extended to deal with double tap as well.
As with earlier patch, new ABI must be documented.  Also we need
a strong argument why the existing ABI is not suitable.

Tap detection algorithms are annoyingly specific to manufacturers
but we did make an effort to come up with a general description a
while back so I'd hope perhaps we can map to that.

> 
> Signed-off-by: Lothar Rubusch <l.rubusch@gmail.com>
> ---
>  drivers/iio/accel/adxl345_core.c | 139 ++++++++++++++++++++++++++++---
>  1 file changed, 127 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/iio/accel/adxl345_core.c b/drivers/iio/accel/adxl345_core.c
> index 7831ec511941..f9e5f47ba303 100644
> --- a/drivers/iio/accel/adxl345_core.c
> +++ b/drivers/iio/accel/adxl345_core.c
> @@ -129,6 +129,29 @@ enum adxl345_axis {
>  	ADXL345_TAP_SUPPRESS = BIT(3),
>  };
>  
> +/* single/double tap */
> +enum adxl345_tap_type {
> +	ADXL345_SINGLE_TAP,
> +	ADXL345_DOUBLE_TAP
trailing comma. Maybe there will be a triple tap sometime.
Anyhow, other than 'terminating' entries we should always have trailing commas.

> +};
> +
> +static const unsigned int adxl345_tap_int_reg[2] = {
> +	[ADXL345_SINGLE_TAP] = ADXL345_INT_SINGLE_TAP,
> +	[ADXL345_DOUBLE_TAP] = ADXL345_INT_DOUBLE_TAP,
> +};
> +
> +enum adxl345_tap_time_type {
> +	ADXL345_TAP_TIME_LATENT,
> +	ADXL345_TAP_TIME_WINDOW,
> +	ADXL345_TAP_TIME_DUR
Comma.

> +};
> +
> +static const unsigned int adxl345_tap_time_reg[3] = {
> +	[ADXL345_TAP_TIME_LATENT] = ADXL345_REG_LATENT,
> +	[ADXL345_TAP_TIME_WINDOW] = ADXL345_REG_WINDOW,
> +	[ADXL345_TAP_TIME_DUR] = ADXL345_REG_DUR,
> +};
> +
>  struct adxl345_state {
>  	const struct adxl345_chip_info *info;
>  	struct regmap *regmap;
> @@ -142,6 +165,8 @@ struct adxl345_state {
>  	u32 tap_axis_ctrl;
>  	u8 tap_threshold;
>  	u32 tap_duration_us;
> +	u32 tap_latent_us;
> +	u32 tap_window_us;
>  
>  	__le16 fifo_buf[ADXL345_DIRS * ADXL345_FIFO_SIZE + 1] __aligned(IIO_DMA_MINALIGN);
>  };
> @@ -154,6 +179,12 @@ static struct iio_event_spec adxl345_events[] = {
>  		.mask_separate = BIT(IIO_EV_INFO_ENABLE),
>  		.mask_shared_by_type = BIT(IIO_EV_INFO_VALUE),
>  	},
> +	{
> +		/* double tap */
> +		.type = IIO_EV_TYPE_GESTURE,
> +		.dir = IIO_EV_DIR_DOUBLETAP,
> +		.mask_shared_by_type = BIT(IIO_EV_INFO_ENABLE),
> +	},
>  };
>  
>  #define ADXL345_CHANNEL(index, reg, axis) {					\
> @@ -250,10 +281,12 @@ static int adxl345_write_tap_axis(struct adxl345_state *st,
>  					     st->tap_axis_ctrl));
>  }
>  

> -static int adxl345_is_tap_en(struct adxl345_state *st, bool *en)
> +static int adxl345_is_tap_en(struct adxl345_state *st,
> +			     enum adxl345_tap_type type, bool *en)
>  {
>  	int ret;
>  	unsigned int regval;
> @@ -280,7 +323,8 @@ static int adxl345_is_tap_en(struct adxl345_state *st, bool *en)
>  	if (ret)
>  		return ret;
>  
> -	*en = FIELD_GET(ADXL345_INT_SINGLE_TAP, regval) > 0;
> +	// TODO FIELD_GET() seems not possible here due to construct 'not const', any ideas?

There is a new function to solve this proposed on list, but not upstream yet.
For now roll your own as you have done.


> +	*en = (adxl345_tap_int_reg[type] & regval) > 0;
>  
>  	return 0;
>  }
> @@ -294,7 +338,12 @@ static int adxl345_set_singletap_en(struct adxl345_state *st,
>  	if (ret)
>  		return ret;
>  
> -	return _adxl345_set_tap_int(st, en);
> +	return _adxl345_set_tap_int(st, ADXL345_SINGLE_TAP, en);
> +}
> +
> +static int adxl345_set_doubletap_en(struct adxl345_state *st, bool en)
> +{
> +	return _adxl345_set_tap_int(st, ADXL345_DOUBLE_TAP, en);
>  }
>  
>  static int adxl345_set_tap_value(struct adxl345_state *st, u8 val)
> @@ -304,19 +353,33 @@ static int adxl345_set_tap_value(struct adxl345_state *st, u8 val)
>  	return regmap_write(st->regmap, ADXL345_REG_THRESH_TAP, min(val, 0xFF));
>  }
>  
> -static int _adxl345_set_tap_time(struct adxl345_state *st, u32 val_us)
> +static int _adxl345_set_tap_time(struct adxl345_state *st,
> +				 enum adxl345_tap_time_type type, u32 val_us)
>  {
>  	unsigned int regval;
>  
> -	st->tap_duration_us = val_us;
> +	switch (type) {
> +	case ADXL345_TAP_TIME_WINDOW:
> +		st->tap_window_us = val_us;
> +		break;
> +	case ADXL345_TAP_TIME_LATENT:
> +		st->tap_latent_us = val_us;
> +		break;
> +	case ADXL345_TAP_TIME_DUR:
> +		st->tap_duration_us = val_us;
> +		break;
> +	}
>  
>  	/*
>  	 * The scale factor is 1250us / LSB for tap_window_us and tap_latent_us.
>  	 * For tap_duration_us the scale factor is 625us / LSB.
>  	 */
> -	regval = DIV_ROUND_CLOSEST(val_us, 625);
> +	if (type == ADXL345_TAP_TIME_DUR)
> +		regval = DIV_ROUND_CLOSEST(val_us, 625);
> +	else
> +		regval = DIV_ROUND_CLOSEST(val_us, 1250);
>  
> -	return regmap_write(st->regmap, ADXL345_REG_DUR, regval);
> +	return regmap_write(st->regmap, adxl345_tap_time_reg[type], regval);
Use this in the earlier patch, even though it would only have one entry at that point.
There is little point in introducing infrastructure that rewrites a patch
just after that patch.  Just put it in the first one with a note
saying it is useful shortly.

>  }
>  
>  static int adxl345_set_tap_duration(struct adxl345_state *st, u32 val_int,
> @@ -330,7 +393,35 @@ static int adxl345_set_tap_duration(struct adxl345_state *st, u32 val_int,
>  	if (val_int || val_fract_us > 159375)
>  		return -EINVAL;
>  
> -	return _adxl345_set_tap_time(st, val_fract_us);
> +	return _adxl345_set_tap_time(st, ADXL345_TAP_TIME_DUR, val_fract_us);
> +}

> @@ -637,9 +735,13 @@ static int adxl345_write_raw_get_fmt(struct iio_dev *indio_dev,
>  	static IIO_DEVICE_ATTR_RW(in_accel_##A##_##C##_##E, 0)
>  
>  ADXL345_generate_iio_dev_attr_FRACTIONAL(gesture_singletap, tap, duration, MICRO, us);
> +ADXL345_generate_iio_dev_attr_FRACTIONAL(gesture_doubletap, tap, window, MICRO, us);
> +ADXL345_generate_iio_dev_attr_FRACTIONAL(gesture_doubletap, tap, latent, MICRO, us);
>  
>  static struct attribute *adxl345_event_attrs[] = {
>  	&iio_dev_attr_in_accel_gesture_singletap_duration_us.dev_attr.attr,
> +	&iio_dev_attr_in_accel_gesture_doubletap_latent_us.dev_attr.attr,
> +	&iio_dev_attr_in_accel_gesture_doubletap_window_us.dev_attr.attr,

As above.  ABI docs missing and times in IIO are all seconds.  us to seconds is easy
given you just use the formatting functions and pass val == 0.

>  	NULL
>  };
>  
> @@ -861,6 +963,17 @@ static int adxl345_push_event(struct iio_dev *indio_dev, int int_stat,
>  			return ret;
>  	}
>  
> +	if (FIELD_GET(ADXL345_INT_DOUBLE_TAP, int_stat)) {
> +		ret = iio_push_event(indio_dev,
> +				     IIO_MOD_EVENT_CODE(IIO_ACCEL, 0,
> +							act_tap_dir,
> +							IIO_EV_TYPE_GESTURE,
> +							IIO_EV_DIR_DOUBLETAP),
> +				     ts);
> +		if (ret)
> +			return ret;
> +	}
> +
>  	return -ENOENT;
>  }
>  
> @@ -965,6 +1078,8 @@ int adxl345_core_probe(struct device *dev, struct regmap *regmap,
>  	/* Init with reasonable values */
>  	st->tap_threshold = 35;			/*   35 [0x23]            */
>  	st->tap_duration_us = 3;		/*    3 [0x03] -> .001875 */
> +	st->tap_window_us = 20;			/*   20 [0x14] -> .025    */
> +	st->tap_latent_us = 20;			/*   20 [0x14] -> .025    */
>  
>  	indio_dev->name = st->info->name;
>  	indio_dev->info = &adxl345_info;