iio: Introduce a new fractional value type
Currently IIO uses a decimal fixed point representations for real type numbers. This patch introduces a new representation for rational type numbers. The number will be expressed by specifying a numerator and denominator. For converting a raw value to a processed value multiply it by the numerator and divide it by the denominator. The reasoning for introducing this new type is that for a lot of devices the scale can be represented easily by a fractional number, but it is not possible to represent it as fixed point number without rounding. E.g. for a simple DAC the scale is often the reference voltage divided by the number of possible values (Usually 2**n_bits - 1). Each driver currently implements the conversion of this fraction to a fixed point number on its own. Also when it comes to the in-kernel interface this allows to directly use the fractional factors to convert a raw value to a processed value. This should on one hand require less instructions and on the other hand increase the precision. Signed-off-by: Lars-Peter Clausen <lars@metafoo.de> Signed-off-by: Jonathan Cameron <jic23@kernel.org>
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@ -366,6 +366,7 @@ static ssize_t iio_read_channel_info(struct device *dev,
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{
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struct iio_dev *indio_dev = dev_to_iio_dev(dev);
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struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
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unsigned long long tmp;
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int val, val2;
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bool scale_db = false;
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int ret = indio_dev->info->read_raw(indio_dev, this_attr->c,
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@ -391,6 +392,11 @@ static ssize_t iio_read_channel_info(struct device *dev,
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return sprintf(buf, "-%d.%09u\n", val, -val2);
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else
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return sprintf(buf, "%d.%09u\n", val, val2);
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case IIO_VAL_FRACTIONAL:
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tmp = div_s64((s64)val * 1000000000LL, val2);
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val2 = do_div(tmp, 1000000000LL);
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val = tmp;
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return sprintf(buf, "%d.%09u\n", val, val2);
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default:
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return 0;
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}
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@ -57,5 +57,6 @@ enum iio_modifier {
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#define IIO_VAL_INT_PLUS_MICRO 2
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#define IIO_VAL_INT_PLUS_NANO 3
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#define IIO_VAL_INT_PLUS_MICRO_DB 4
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#define IIO_VAL_FRACTIONAL 10
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#endif /* _IIO_TYPES_H_ */
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