lis3: scale output values to mg

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>
Acked-by: Éric Piel <Eric.Piel@tremplin-utc.net>
Cc: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 31 insertions, 3 deletions

diff --git a/drivers/hwmon/lis3lv02d.c b/drivers/hwmon/lis3lv02d.c
index ba97ed8516bf..b2f2277cad3c 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 f73c78603732..e6a01f44709b 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 */