Re: [PATCH 01/16] iio: hid-sensors: Convert units and exponent

[Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>]

On 04/23/2014 01:57 PM, Jonathan Cameron wrote:
> On 19/04/14 00:22, Srinivas Pandruvada wrote:
>> HID sensor hub specify a default unit and alternative units. This
>> along with unit exponent can be used adjust scale. This change
>> change HID sensor data units to IIO defined units for each
>> sensor type. So in this way user space can use a simply use:
>> "(data + offset) * scale" to get final result.
>>
>> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
>
> Hi Srinivas,
>
> What 'grief' is this abi change likely to cause us?
>
Hi Jonathan,

Since the products are just released with the hubs, I don't think there 
is much impact.
I have notified few users I knew, who pointed me about this disparity.


Thanks,
Srinivas
> I know I effectively asked you to fix this, but I'd like to get
> a handle on just how many people are likely to shout.
>
> The original code is a gross breaking of the published ABI so
> it probably is reasonable to change it...
>
> I'm too tired to review this properly right now so only the most
> superficial comments in line.
>> ---
>>   .../iio/common/hid-sensors/hid-sensor-attributes.c | 114 
>> +++++++++++++++++++++
>>   include/linux/hid-sensor-hub.h                     |   4 +
>>   2 files changed, 118 insertions(+)
>>
>> diff --git a/drivers/iio/common/hid-sensors/hid-sensor-attributes.c 
>> b/drivers/iio/common/hid-sensors/hid-sensor-attributes.c
>> index 75b5473..451a95b 100644
>> --- a/drivers/iio/common/hid-sensors/hid-sensor-attributes.c
>> +++ b/drivers/iio/common/hid-sensors/hid-sensor-attributes.c
>> @@ -26,6 +26,40 @@
>>   #include <linux/iio/iio.h>
>>   #include <linux/iio/sysfs.h>
>>
>> +struct {
>> +    u32 usage_id;
>> +    int unit; /* 0 for default others from HID sensor spec */
>> +    int scale_val0; /* scale, whole number */
>> +    int scale_val1; /* scale, fraction in micros */
>> +} unit_conversion[] = {
>> +    {HID_USAGE_SENSOR_ACCEL_3D, 0, 9, 806650},
>> +    {HID_USAGE_SENSOR_ACCEL_3D,
>> +        HID_USAGE_SENSOR_UNITS_METERS_PER_SEC_SQRD, 1, 0},
>> +    {HID_USAGE_SENSOR_ACCEL_3D,
>> +        HID_USAGE_SENSOR_UNITS_G, 9, 806650},
>> +
>> +    {HID_USAGE_SENSOR_GYRO_3D, 0, 0, 17453},
>> +    {HID_USAGE_SENSOR_GYRO_3D,
>> +        HID_USAGE_SENSOR_UNITS_RADIANS_PER_SECOND, 1, 0},
>> +    {HID_USAGE_SENSOR_GYRO_3D,
>> +        HID_USAGE_SENSOR_UNITS_DEGREES_PER_SECOND, 0, 17453},
>> +
>> +    {HID_USAGE_SENSOR_COMPASS_3D, 0, 1000, 0},
>> +    {HID_USAGE_SENSOR_COMPASS_3D, HID_USAGE_SENSOR_UNITS_GAUSS, 1, 0},
>> +
>> +    {HID_USAGE_SENSOR_INCLINOMETER_3D, 0, 17453, 0},
>> +    {HID_USAGE_SENSOR_INCLINOMETER_3D,
>> +        HID_USAGE_SENSOR_UNITS_DEGREES, 0, 17453},
>> +    {HID_USAGE_SENSOR_INCLINOMETER_3D,
>> +        HID_USAGE_SENSOR_UNITS_RADIANS, 1, 0},
>> +
>> +    {HID_USAGE_SENSOR_ALS, 0, 1, 0},
>> +    {HID_USAGE_SENSOR_ALS, HID_USAGE_SENSOR_UNITS_LUX, 1, 0},
>> +
>> +    {HID_USAGE_SENSOR_PRESSURE, 0, 100000, 0},
>> +    {HID_USAGE_SENSOR_PRESSURE, HID_USAGE_SENSOR_UNITS_PASCAL, 1, 0},
>> +};
>> +
>>   static int pow_10(unsigned power)
>>   {
>>       int i;
>> @@ -209,6 +243,86 @@ int hid_sensor_write_raw_hyst_value(struct 
>> hid_sensor_common *st,
>>   }
>>   EXPORT_SYMBOL(hid_sensor_write_raw_hyst_value);
>>
>> +/*
>> + * This fuction applies the unit exponent to the scale.
> function.
>
> Good examples btw.
>> + * For example:
>> + * 9.806650 ->exp:2-> val0[980]val1[6650]
>> + * 9.000806 ->exp:2-> val0[900]val1[806]
>> + * 0.174535 ->exp:2-> val0[17]val1[4535]
>> + * 1.001745 ->exp:0-> val0[1]val1[1745]
>> + * 1.001745 ->exp:2-> val0[100]val1[1745]
>> + * 1.001745 ->exp:4-> val0[10017]val1[45]
>> + * 9.806650 ->exp:-2-> val0[0]val1[98066]
>> + */
>> +static void adjust_exponent_micro(int *val0, int *val1, int scale0,
>> +                  int scale1, int exp)
>> +{
>> +    int i;
>> +    int x;
>> +    int res;
>> +    int rem;
>> +
>> +    if (exp > 0) {
>> +        *val0 = scale0 * pow_10(exp);
>> +        res = 0;
>> +        if (exp > 6) {
>> +            *val1 = 0;
>> +            return;
>> +        }
>> +        for (i = 0; i < exp; ++i) {
>> +            x = scale1 / pow_10(5 - i);
>> +            res += (pow_10(exp - 1 - i) * x);
>> +            scale1 = scale1 % pow_10(5 - i);
>> +        }
>> +        *val0 += res;
>> +            *val1 = scale1 * pow_10(exp);
>> +    } else if (exp < 0) {
>> +        exp = abs(exp);
>> +        if (exp > 6) {
>> +            *val0 = *val1 = 0;
>> +            return;
>> +        }
>> +        *val0 = scale0 / pow_10(exp);
>> +        rem = scale0 % pow_10(exp);
>> +        res = 0;
>> +        for (i = 0; i < (6 - exp); ++i) {
>> +            x = scale1 / pow_10(5 - i);
>> +            res += (pow_10(5 - exp - i) * x);
>> +            scale1 = scale1 % pow_10(5 - i);
>> +        }
>> +        *val1 = rem * pow_10(6 - exp) + res;
>> +    } else {
>> +        *val0 = scale0;
>> +        *val1 = scale1;
>> +    }
>> +}
>> +
>> +int hid_sensor_format_scale(u32 usage_id,
>> +            struct hid_sensor_hub_attribute_info *attr_info,
>> +            int *val0, int *val1)
>> +{
>> +    int i;
>> +    int exp;
>> +
>> +    *val0 = 1;
>> +    *val1 = 0;
>> +
>> +    for (i = 0; ARRAY_SIZE(unit_conversion); ++i) {
>> +        if (unit_conversion[i].usage_id == usage_id &&
>> +            unit_conversion[i].unit == attr_info->units) {
>> +            exp  = hid_sensor_convert_exponent(
>> +                        attr_info->unit_expo);
>> +            adjust_exponent_micro(val0, val1,
>> +                    unit_conversion[i].scale_val0,
>> +                    unit_conversion[i].scale_val1, exp);
>> +            break;
>> +        }
>> +    }
>> +
>> +    return IIO_VAL_INT_PLUS_MICRO;
>> +}
>> +EXPORT_SYMBOL(hid_sensor_format_scale);
>> +
>>   int hid_sensor_parse_common_attributes(struct hid_sensor_hub_device 
>> *hsdev,
>>                       u32 usage_id,
>>                       struct hid_sensor_common *st)
>> diff --git a/include/linux/hid-sensor-hub.h 
>> b/include/linux/hid-sensor-hub.h
>> index b70cfd7..89626b2 100644
>> --- a/include/linux/hid-sensor-hub.h
>> +++ b/include/linux/hid-sensor-hub.h
>> @@ -223,4 +223,8 @@ int hid_sensor_read_samp_freq_value(struct 
>> hid_sensor_common *st,
>>   int hid_sensor_get_usage_index(struct hid_sensor_hub_device *hsdev,
>>                   u32 report_id, int field_index, u32 usage_id);
>>
>> +int hid_sensor_format_scale(u32 usage_id,
>> +                struct hid_sensor_hub_attribute_info *attr_info,
>> +                int *val0, int *val1);
>> +
>>   #endif
>>
>
>