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Date: Sun, 15 Nov 2009 16:32:02 +0100
From: Éric Piel <eric.piel@...mplin-utc.net>
To: Samu Onkalo <samu.p.onkalo@...ia.com>
Cc: daniel@...aq.de, pavel@....cz, linux-kernel@...r.kernel.org,
lm-sensors@...sensors.org
Subject: Re: [PATCH v2 09/10] lis3: Scale output values to mg
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@...ia.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 */
--
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