Re: [PATCH v2 09/10] lis3: Scale output values to mg

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

Op 10-11-09 13:41, Samu Onkalo schreef:
> Report output values as 1/1000 of earth gravity.
After the discussion started by Daniel, I'm willing to accept this patch
"as is", just with a better log explaining why it's ok to break
userspace ABI:
 * the sysfs "position" attribute was never safe to be read as it could
have different scales depending on the underlying hardware. It's now
featuring a consistent scale, which is more or less identical to the one
used by the 12-bits sensors
 * the joystick interface reports the same values as before, excepted of
course if "raw" values are requested, in which case the same remark as
for "position" applies.

Eric

> 
> Signed-off-by: Samu Onkalo <samu.p.onkalo@nokia.com>
> ---
>  drivers/hwmon/lis3lv02d.c |   31 ++++++++++++++++++++++++++++---
>  drivers/hwmon/lis3lv02d.h |    4 ++++
>  2 files changed, 32 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/hwmon/lis3lv02d.c b/drivers/hwmon/lis3lv02d.c
> index be2eb97..7e72836 100644
> --- a/drivers/hwmon/lis3lv02d.c
> +++ b/drivers/hwmon/lis3lv02d.c
> @@ -53,6 +53,19 @@
>  #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
> + * SCALING_ACCURACY is used to increase accuracy of the intermediate
> + * calculation results.
> + */
> +#define LIS3_SCALING_ACCURACY           1024
> +#define LIS3_2G2G_SENSITIVITY_WAI_12B	((LIS3_SCALING_ACCURACY * 1000) / 1024)
> +#define LIS3_2G2G_SENSITIVITY_WAI_8B	(18 * LIS3_SCALING_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),
>  };
> @@ -105,11 +118,16 @@ 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;
>  
>  	position[0] = lis3->read_data(lis3, OUTX);
>  	position[1] = lis3->read_data(lis3, OUTY);
>  	position[2] = lis3->read_data(lis3, OUTZ);
>  
> +	for (i = 0; i < 3; i++)
> +		position[i] = (position[i] * lis3->scale) /
> +			LIS3_SCALING_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);
> @@ -385,6 +403,7 @@ int lis3lv02d_joystick_enable(void)
>  {
>  	struct input_dev *input_dev;
>  	int err;
> +	int max_val, fuzz, flat;
>  
>  	if (lis3_dev.idev)
>  		return -EINVAL;
> @@ -404,9 +423,13 @@ 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_SCALING_ACCURACY;
> +	fuzz = (LIS3_DEFAULT_FUZZ * lis3_dev.scale)  / LIS3_SCALING_ACCURACY;
> +	flat = (LIS3_DEFAULT_FLAT * lis3_dev.scale) / LIS3_SCALING_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) {
> @@ -521,12 +544,14 @@ int lis3lv02d_init_device(struct lis3lv02d *dev)
>  		dev->read_data = lis3lv02d_read_12;
>  		dev->mdps_max_val = 2048;
>  		dev->pwron_delay = LIS3_PWRON_DELAY_WAI_12B;
> +		dev->scale = LIS3_2G2G_SENSITIVITY_WAI_12B;
>  		break;
>  	case WAI_8B:
>  		printk(KERN_INFO DRIVER_NAME ": 8 bits sensor found\n");
>  		dev->read_data = lis3lv02d_read_8;
>  		dev->mdps_max_val = 128;
>  		dev->pwron_delay = LIS3_PWRON_DELAY_WAI_8B;
> +		dev->scale = LIS3_2G2G_SENSITIVITY_WAI_8B;
>  		break;
>  	default:
>  		printk(KERN_ERR DRIVER_NAME
> diff --git a/drivers/hwmon/lis3lv02d.h b/drivers/hwmon/lis3lv02d.h
> index a692116..42618b8 100644
> --- a/drivers/hwmon/lis3lv02d.h
> +++ b/drivers/hwmon/lis3lv02d.h
> @@ -212,6 +212,10 @@ 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 */