iio: Introduce a new fractional value type

xiaomi-sm8450/android_kernel_xiaomi_sm8450

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>

This commit is contained in:

Lars-Peter Clausen

2012-09-14 16:21:00 +01:00

committed by

Jonathan Cameron

parent ca7d1b32d2

commit 7985e7c100

2 changed files with 7 additions and 0 deletions

									
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include/linux/iio/types.h
									
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				@@ -57,5 +57,6 @@ enum iio_modifier {

				#define IIO_VAL_INT_PLUS_MICRO 2

				#define IIO_VAL_INT_PLUS_NANO 3

				#define IIO_VAL_INT_PLUS_MICRO_DB 4

				#define IIO_VAL_FRACTIONAL 10

				#endif /* _IIO_TYPES_H_ */

iio: Introduce a new fractional value type

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include/linux/iio/types.h

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