Re: [PATCH v4] iio: mma8452: add freefall detection for Freescale's accelerometers

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Hello,

> This adds freefall event detection to the supported devices. It adds
> the in_accel_x&y&z_mag_falling_en iio event attribute, which activates
> freefall mode.
> 
> In freefall mode, the current acceleration magnitude (AND combination
> of all axis values) is compared to the specified threshold.
> If it falls under the threshold (in_accel_mag_falling_value),
> the appropriate IIO event code is generated.
> 
> This is what the sysfs "events" directory for these devices looks
> like after this change:
> 
> -rw-r--r--    4096 Oct 23 08:45 in_accel_mag_falling_period
> -rw-r--r--    4096 Oct 23 08:45 in_accel_mag_falling_value
> -rw-r--r--    4096 Oct 23 08:45 in_accel_mag_rising_period
> -rw-r--r--    4096 Oct 23 08:45 in_accel_mag_rising_value
> -r--r--r--    4096 Oct 23 08:45 in_accel_scale
> -rw-r--r--    4096 Oct 23 08:45 in_accel_x&y&z_mag_falling_en
> -rw-r--r--    4096 Oct 23 08:45 in_accel_x_mag_rising_en
> -rw-r--r--    4096 Oct 23 08:45 in_accel_y_mag_rising_en
> -rw-r--r--    4096 Oct 23 08:45 in_accel_z_mag_rising_en

I think it is a very good idea to have this for review, thanks!

minor comments below

> Signed-off-by: Martin Kepplinger <martin.kepplinger@xxxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Christoph Muellner <christoph.muellner@xxxxxxxxxxxxxxxxxxxxx>
> ---
> revision history
> ----------------
> v1:
>         initial post
> v2:
>         build all from correct event and channel spec structs
> v3:
>         rising and falling are treated as equal now. Until last time, I had
>         misunderstood the iio events' user API definition. This works and
>         values always reflect the current state of operation.
> v4:
> 	fix error that caused a build warning
> 
>  drivers/iio/accel/mma8452.c | 156 +++++++++++++++++++++++++++++++++++++++-----
>  1 file changed, 139 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/iio/accel/mma8452.c b/drivers/iio/accel/mma8452.c
> index ccc632a..9534c3a 100644
> --- a/drivers/iio/accel/mma8452.c
> +++ b/drivers/iio/accel/mma8452.c
> @@ -15,7 +15,7 @@
>   *
>   * 7-bit I2C slave address 0x1c/0x1d (pin selectable)
>   *
> - * TODO: orientation / freefall events, autosleep
> + * TODO: orientation events, autosleep
>   */
>  
>  #include <linux/module.h>
> @@ -416,6 +416,46 @@ fail:
>  	return ret;
>  }
>  
> +static int mma8452_freefall_mode_enabled(struct mma8452_data *data)
> +{
> +	int val;
> +	const struct mma_chip_info *chip = data->chip_info;
> +
> +	val = i2c_smbus_read_byte_data(data->client, chip->ev_cfg);
> +	if (val < 0)
> +		return val;
> +
> +	return !(val & MMA8452_FF_MT_CFG_OAE);

I'd appreciate a comment what the possible return values of this function 
are and their purpose

> +}
> +
> +static int mma8452_set_freefall_mode(struct mma8452_data *data, u8 state)

state seems to be used as a bool, maybe it should be bool

> +{
> +	int val, ret;

strictly, only one of the two variable is necessary

> +	const struct mma_chip_info *chip = data->chip_info;
> +
> +	val = i2c_smbus_read_byte_data(data->client, chip->ev_cfg);
> +	if (val < 0)
> +		return val;
> +
> +	if (state && !(mma8452_freefall_mode_enabled(data))) {
> +		val |= BIT(idx_x + chip->ev_cfg_chan_shift);
> +		val |= BIT(idx_y + chip->ev_cfg_chan_shift);
> +		val |= BIT(idx_z + chip->ev_cfg_chan_shift);
> +		val &= ~MMA8452_FF_MT_CFG_OAE;
> +	} else if (!state && mma8452_freefall_mode_enabled(data)) {
> +		val &= ~BIT(idx_x + chip->ev_cfg_chan_shift);
> +		val &= ~BIT(idx_y + chip->ev_cfg_chan_shift);
> +		val &= ~BIT(idx_z + chip->ev_cfg_chan_shift);
> +		val |= MMA8452_FF_MT_CFG_OAE;
> +	}
> +
> +	ret = mma8452_change_config(data, chip->ev_cfg, val);
> +	if (ret)
> +		return ret;
> +
> +	return 0;
> +}
> +
>  static int mma8452_set_hp_filter_frequency(struct mma8452_data *data,
>  					   int val, int val2)
>  {
> @@ -609,12 +649,22 @@ static int mma8452_read_event_config(struct iio_dev *indio_dev,

I find the return values of this functions difficult to understand, 
comment would be good

>  	const struct mma_chip_info *chip = data->chip_info;
>  	int ret;
>  
> -	ret = i2c_smbus_read_byte_data(data->client,
> -				       data->chip_info->ev_cfg);
> -	if (ret < 0)
> -		return ret;
> +	switch (dir) {
> +	case IIO_EV_DIR_FALLING:
> +		return mma8452_freefall_mode_enabled(data);
> +	case IIO_EV_DIR_RISING:
> +		if (mma8452_freefall_mode_enabled(data))
> +			return 0;
> +
> +		ret = i2c_smbus_read_byte_data(data->client,
> +					       data->chip_info->ev_cfg);
> +		if (ret < 0)
> +			return ret;
>  
> -	return !!(ret & BIT(chan->scan_index + chip->ev_cfg_chan_shift));
> +		return !!(ret & BIT(chan->scan_index + chip->ev_cfg_chan_shift));
> +	default:
> +		return -EINVAL;
> +	}
>  }
>  
>  static int mma8452_write_event_config(struct iio_dev *indio_dev,
> @@ -627,19 +677,34 @@ static int mma8452_write_event_config(struct iio_dev *indio_dev,
>  	const struct mma_chip_info *chip = data->chip_info;
>  	int val;
>  
> -	val = i2c_smbus_read_byte_data(data->client, chip->ev_cfg);
> -	if (val < 0)
> -		return val;
> -
> -	if (state)
> -		val |= BIT(chan->scan_index + chip->ev_cfg_chan_shift);
> -	else
> -		val &= ~BIT(chan->scan_index + chip->ev_cfg_chan_shift);
> +	switch (dir) {
> +	case IIO_EV_DIR_FALLING:
> +		return mma8452_set_freefall_mode(data, state);
> +	case IIO_EV_DIR_RISING:
> +		val = i2c_smbus_read_byte_data(data->client, chip->ev_cfg);
> +		if (val < 0)
> +			return val;
> +
> +		if (state) {
> +			if (mma8452_freefall_mode_enabled(data)) {
> +				val &= ~BIT(idx_x + chip->ev_cfg_chan_shift);
> +				val &= ~BIT(idx_y + chip->ev_cfg_chan_shift);
> +				val &= ~BIT(idx_z + chip->ev_cfg_chan_shift);
> +				val |= MMA8452_FF_MT_CFG_OAE;
> +			}
> +			val |= BIT(chan->scan_index + chip->ev_cfg_chan_shift);
> +		} else {
> +			if (mma8452_freefall_mode_enabled(data))
> +				return -EBUSY;
> +			val &= ~BIT(chan->scan_index + chip->ev_cfg_chan_shift);
> +		}
>  
> -	val |= chip->ev_cfg_ele;
> -	val |= MMA8452_FF_MT_CFG_OAE;
> +		val |= chip->ev_cfg_ele;
>  
> -	return mma8452_change_config(data, chip->ev_cfg, val);
> +		return mma8452_change_config(data, chip->ev_cfg, val);
> +	default:
> +		return -EINVAL;
> +	}
>  }
>  
>  static void mma8452_transient_interrupt(struct iio_dev *indio_dev)
> @@ -652,6 +717,16 @@ static void mma8452_transient_interrupt(struct iio_dev *indio_dev)
>  	if (src < 0)
>  		return;
>  
> +	if (mma8452_freefall_mode_enabled(data)) {
> +		iio_push_event(indio_dev,
> +			       IIO_MOD_EVENT_CODE(IIO_ACCEL, 0,
> +						  IIO_MOD_X_AND_Y_AND_Z,
> +						  IIO_EV_TYPE_MAG,
> +						  IIO_EV_DIR_FALLING),
> +			       ts);
> +		return;
> +	}
> +
>  	if (src & data->chip_info->ev_src_xe)
>  		iio_push_event(indio_dev,
>  			       IIO_MOD_EVENT_CODE(IIO_ACCEL, 0, IIO_MOD_X,
> @@ -745,6 +820,27 @@ static int mma8452_reg_access_dbg(struct iio_dev *indio_dev,
>  	return 0;
>  }
>  
> +static const struct iio_event_spec mma8452_freefall_event[] = {
> +	{
> +		.type = IIO_EV_TYPE_MAG,
> +		.dir = IIO_EV_DIR_FALLING,
> +		.mask_separate = BIT(IIO_EV_INFO_ENABLE),
> +		.mask_shared_by_type = BIT(IIO_EV_INFO_VALUE) |
> +					BIT(IIO_EV_INFO_PERIOD) |
> +					BIT(IIO_EV_INFO_HIGH_PASS_FILTER_3DB)
> +	},
> +};
> +
> +static const struct iio_event_spec mma8652_freefall_event[] = {
> +	{
> +		.type = IIO_EV_TYPE_MAG,
> +		.dir = IIO_EV_DIR_FALLING,
> +		.mask_separate = BIT(IIO_EV_INFO_ENABLE),
> +		.mask_shared_by_type = BIT(IIO_EV_INFO_VALUE) |
> +					BIT(IIO_EV_INFO_PERIOD)
> +	},
> +};
> +
>  static const struct iio_event_spec mma8452_transient_event[] = {
>  	{
>  		.type = IIO_EV_TYPE_MAG,
> @@ -781,6 +877,24 @@ static struct attribute_group mma8452_event_attribute_group = {
>  	.attrs = mma8452_event_attributes,
>  };
>  
> +#define MMA8452_FREEFALL_CHANNEL(modifier) { \
> +	.type = IIO_ACCEL, \
> +	.modified = 1, \
> +	.channel2 = modifier, \
> +	.scan_index = -1, \
> +	.event_spec = mma8452_freefall_event, \
> +	.num_event_specs = ARRAY_SIZE(mma8452_freefall_event), \
> +}
> +
> +#define MMA8652_FREEFALL_CHANNEL(modifier) { \
> +	.type = IIO_ACCEL, \
> +	.modified = 1, \
> +	.channel2 = modifier, \
> +	.scan_index = -1, \
> +	.event_spec = mma8652_freefall_event, \
> +	.num_event_specs = ARRAY_SIZE(mma8652_freefall_event), \
> +}
> +
>  #define MMA8452_CHANNEL(axis, idx, bits) { \
>  	.type = IIO_ACCEL, \
>  	.modified = 1, \
> @@ -827,6 +941,7 @@ static const struct iio_chan_spec mma8452_channels[] = {
>  	MMA8452_CHANNEL(Y, idx_y, 12),
>  	MMA8452_CHANNEL(Z, idx_z, 12),
>  	IIO_CHAN_SOFT_TIMESTAMP(idx_ts),
> +	MMA8452_FREEFALL_CHANNEL(IIO_MOD_X_AND_Y_AND_Z),
>  };
>  
>  static const struct iio_chan_spec mma8453_channels[] = {
> @@ -834,6 +949,7 @@ static const struct iio_chan_spec mma8453_channels[] = {
>  	MMA8452_CHANNEL(Y, idx_y, 10),
>  	MMA8452_CHANNEL(Z, idx_z, 10),
>  	IIO_CHAN_SOFT_TIMESTAMP(idx_ts),
> +	MMA8452_FREEFALL_CHANNEL(IIO_MOD_X_AND_Y_AND_Z),
>  };
>  
>  static const struct iio_chan_spec mma8652_channels[] = {
> @@ -841,6 +957,7 @@ static const struct iio_chan_spec mma8652_channels[] = {
>  	MMA8652_CHANNEL(Y, idx_y, 12),
>  	MMA8652_CHANNEL(Z, idx_z, 12),
>  	IIO_CHAN_SOFT_TIMESTAMP(idx_ts),
> +	MMA8652_FREEFALL_CHANNEL(IIO_MOD_X_AND_Y_AND_Z),
>  };
>  
>  static const struct iio_chan_spec mma8653_channels[] = {
> @@ -848,6 +965,7 @@ static const struct iio_chan_spec mma8653_channels[] = {
>  	MMA8652_CHANNEL(Y, idx_y, 10),
>  	MMA8652_CHANNEL(Z, idx_z, 10),
>  	IIO_CHAN_SOFT_TIMESTAMP(idx_ts),
> +	MMA8652_FREEFALL_CHANNEL(IIO_MOD_X_AND_Y_AND_Z),
>  };
>  
>  enum {
> @@ -1190,6 +1308,10 @@ static int mma8452_probe(struct i2c_client *client,
>  	if (ret < 0)
>  		goto buffer_cleanup;
>  
> +	ret = mma8452_set_freefall_mode(data, 0);
> +	if (ret)
> +		return ret;
> +
>  	return 0;
>  
>  buffer_cleanup:
> 

-- 

Peter Meerwald-Stadler
+43-664-2444418 (mobile)
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