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

[Jonathan Cameron <jic23@kernel.org>]

On 26/04/14 20:34, Srinivas Pandruvada wrote:
>
> On 04/25/2014 11:30 AM, 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>
>> see inline.
Applied to the togreg branch of iio.git with a tweaks to comments as mentioned
(please check I didn't mess them up!)

>>> ---
>>>   .../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.
>>> + * For example:
>> Function
>>> + * 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]
>> It took me a while to get what you meant here, perhaps for the examples it
>> is worth showing the actual value directly as well. Maybe.
>> 9.806650 exp:2->980.6650 -> val0[980]val1[665000] (note the above is I think
>> incorrect due to lack of trailing zeros on val1.
>>> + */
>>> +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;
>>> +        }
>> so if example 1 above..
>> val0 = 900 as desired.
>> i  = 0;
>> sca1e1 = 806650
>> x = 806650/100000 = 8;
>> res = 80;
>> scale1 = 06650
>> i = 1
>> x = 06650/10000 = 0;
>> res = 80;
>>  so 980. Good.
>>> +        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);
>> val1 = 665000 which is correct with the trailing zeros in val2.
>> So your code is good but examples need those zeros!
> Impressive, Absolutely great review. I will correct comments in the next version.
Given this was the only issue in the patch set I'll just fix it up as I merge
it.

It's been a couple of weeks an noone else has chipped in on this series, so
I'm taking it now.


>
> Thanks,
> Srinivas
>>
>>> +    } 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
>>>
>>
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>