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Date: Tue, 01 Dec 2009 09:53:33 +0100
From: Éric Piel <Eric.Piel@...mplin-utc.net>
To: Samu Onkalo <samu.p.onkalo@...ia.com>
Cc: linux-kernel@...r.kernel.org, lm-sensors@...sensors.org
Subject: Re: [PATCH v4 4/5] lis3: Scale output values to mg
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@...ia.com>
Signed-off-by: Éric Piel <eric.piel@...mplin-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 */
--
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