Re: [PATCH v4 4/5] lis3: Scale output values to mg

["Éric Piel" <Eric.Piel@tremplin-utc.net>]

Op 01-12-09 09:33, Samu Onkalo schreef:
> Report output values as 1/1000 of earth gravity.
>
> Output values from lis3 can be read from sysfs position entry and
> from input device. Input device can be accessed as event device
> and as joystick device. Joystick device can be in two modes. Meaning of the
> output values varies from case to case depending on the chip type
> and configuration (scale). Only joystick interface in JS_CORR_BROKEN mode
> returned somehow similar output values in different configurations.
> Joystick device is in that state by default in case of lis3.
>
> Position sysfs entry, input event device and raw joystick device
> have been little bit broken since meaning of the output values has been
> varied between 12 and 8 bit devices. Applications which relayed on those
> methods failed if the chip is different than the expected one.
>
> This patch converts output values to mean similar thing in different
> configurations. Both 8 and 12 bit devices reports now same acceleration values.
> If somebody implements full scale support to the driver, output values will
> still mean the same. Scaling factor and input device range must be updated
> in that case.
>
> Joystick interface in JS_CORR_BROKEN mode is not touched by this patch.
> All other interfaces have different scale after this change.
> For 12 bit device scaling factor is 0.977 which keeps scaled and unscaled
> values are quite close to each others.
> For 8 bit device, scaled values are 18 times bigger than unscaled values.
>
> Signed-off-by: Samu Onkalo<samu.p.onkalo@nokia.com>
Signed-off-by: Éric Piel <eric.piel@tremplin-utc.net>

> ---
>   drivers/hwmon/lis3lv02d.c |   30 +++++++++++++++++++++++++++---
>   drivers/hwmon/lis3lv02d.h |    4 ++++
>   2 files changed, 31 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/hwmon/lis3lv02d.c b/drivers/hwmon/lis3lv02d.c
> index ba97ed8..b2f2277 100644
> --- a/drivers/hwmon/lis3lv02d.c
> +++ b/drivers/hwmon/lis3lv02d.c
> @@ -53,6 +53,20 @@
>   #define LIS3_PWRON_DELAY_WAI_12B	(5000)
>   #define LIS3_PWRON_DELAY_WAI_8B		(3000)
>
> +/*
> + * LIS3LV02D spec says 1024 LSBs corresponds 1 G ->  1LSB is 1000/1024 mG
> + * LIS302D spec says: 18 mG / digit
> + * LIS3_ACCURACY is used to increase accuracy of the intermediate
> + * calculation results.
> + */
> +#define LIS3_ACCURACY			1024
> +/* Sensitivity values for -2G +2G scale */
> +#define LIS3_SENSITIVITY_12B		((LIS3_ACCURACY * 1000) / 1024)
> +#define LIS3_SENSITIVITY_8B		(18 * LIS3_ACCURACY)
> +
> +#define LIS3_DEFAULT_FUZZ		3
> +#define LIS3_DEFAULT_FLAT		3
> +
>   struct lis3lv02d lis3_dev = {
>   	.misc_wait   = __WAIT_QUEUE_HEAD_INITIALIZER(lis3_dev.misc_wait),
>   };
> @@ -105,6 +119,7 @@ static inline int lis3lv02d_get_axis(s8 axis, int hw_values[3])
>   static void lis3lv02d_get_xyz(struct lis3lv02d *lis3, int *x, int *y, int *z)
>   {
>   	int position[3];
> +	int i;
>
>   	mutex_lock(&lis3->mutex);
>   	position[0] = lis3->read_data(lis3, OUTX);
> @@ -112,6 +127,9 @@ static void lis3lv02d_get_xyz(struct lis3lv02d *lis3, int *x, int *y, int *z)
>   	position[2] = lis3->read_data(lis3, OUTZ);
>   	mutex_unlock(&lis3->mutex);
>
> +	for (i = 0; i<  3; i++)
> +		position[i] = (position[i] * lis3->scale) / LIS3_ACCURACY;
> +
>   	*x = lis3lv02d_get_axis(lis3->ac.x, position);
>   	*y = lis3lv02d_get_axis(lis3->ac.y, position);
>   	*z = lis3lv02d_get_axis(lis3->ac.z, position);
> @@ -377,6 +395,7 @@ int lis3lv02d_joystick_enable(void)
>   {
>   	struct input_dev *input_dev;
>   	int err;
> +	int max_val, fuzz, flat;
>
>   	if (lis3_dev.idev)
>   		return -EINVAL;
> @@ -396,9 +415,12 @@ int lis3lv02d_joystick_enable(void)
>   	input_dev->dev.parent =&lis3_dev.pdev->dev;
>
>   	set_bit(EV_ABS, input_dev->evbit);
> -	input_set_abs_params(input_dev, ABS_X, -lis3_dev.mdps_max_val, lis3_dev.mdps_max_val, 3, 3);
> -	input_set_abs_params(input_dev, ABS_Y, -lis3_dev.mdps_max_val, lis3_dev.mdps_max_val, 3, 3);
> -	input_set_abs_params(input_dev, ABS_Z, -lis3_dev.mdps_max_val, lis3_dev.mdps_max_val, 3, 3);
> +	max_val = (lis3_dev.mdps_max_val * lis3_dev.scale) / LIS3_ACCURACY;
> +	fuzz = (LIS3_DEFAULT_FUZZ * lis3_dev.scale) / LIS3_ACCURACY;
> +	flat = (LIS3_DEFAULT_FLAT * lis3_dev.scale) / LIS3_ACCURACY;
> +	input_set_abs_params(input_dev, ABS_X, -max_val, max_val, fuzz, flat);
> +	input_set_abs_params(input_dev, ABS_Y, -max_val, max_val, fuzz, flat);
> +	input_set_abs_params(input_dev, ABS_Z, -max_val, max_val, fuzz, flat);
>
>   	err = input_register_polled_device(lis3_dev.idev);
>   	if (err) {
> @@ -515,6 +537,7 @@ int lis3lv02d_init_device(struct lis3lv02d *dev)
>   		dev->pwron_delay = LIS3_PWRON_DELAY_WAI_12B;
>   		dev->odrs = lis3_12_rates;
>   		dev->odr_mask = CTRL1_DF0 | CTRL1_DF1;
> +		dev->scale = LIS3_SENSITIVITY_12B;
>   		break;
>   	case WAI_8B:
>   		printk(KERN_INFO DRIVER_NAME ": 8 bits sensor found\n");
> @@ -523,6 +546,7 @@ int lis3lv02d_init_device(struct lis3lv02d *dev)
>   		dev->pwron_delay = LIS3_PWRON_DELAY_WAI_8B;
>   		dev->odrs = lis3_8_rates;
>   		dev->odr_mask = CTRL1_DR;
> +		dev->scale = LIS3_SENSITIVITY_8B;
>   		break;
>   	default:
>   		printk(KERN_ERR DRIVER_NAME
> diff --git a/drivers/hwmon/lis3lv02d.h b/drivers/hwmon/lis3lv02d.h
> index f73c786..e6a01f4 100644
> --- a/drivers/hwmon/lis3lv02d.h
> +++ b/drivers/hwmon/lis3lv02d.h
> @@ -214,6 +214,10 @@ struct lis3lv02d {
>   	s16 (*read_data) (struct lis3lv02d *lis3, int reg);
>   	int			mdps_max_val;
>   	int			pwron_delay;
> +	int                     scale; /*
> +					* relationship between 1 LBS and mG
> +					* (1/1000th of earth gravity)
> +					*/
>
>   	struct input_polled_dev	*idev;     /* input device */
>   	struct platform_device	*pdev;     /* platform device */