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CODING_CONVENTIONS.md: add a note about float

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Floating point math should be avoided in the embedded space.
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Benjamin Valentin 2020-07-14 20:39:02 +02:00
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commit 7c4097bd52
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CODING_CONVENTIONS.md
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@ -7,6 +7,15 @@
* Avoid dynamic memory allocation (malloc/free, new, etc.)! It will break * Avoid dynamic memory allocation (malloc/free, new, etc.)! It will break
real-time guarantees, increase code complexity, and make it more likely to use real-time guarantees, increase code complexity, and make it more likely to use
more memory than available. more memory than available.
* Avoid the use of floating point arithmetic. Not every MCU has a FPU and software
floating point libraries cause unnecessary overhead.
Instead use fixed-point integers and transform equations so that they stay within
the range of integer math.
An easy way to ensure this is by multiplying by a constant factor, ideally a power
of two - this is a simple shift operation.
Take care that intermediate values do not exceed the range of the data type you are using.
When writing drivers, do not convert the measurement data into float, but instead
choose an appropriate integer format / SI prefix.
* Please obey the Linux coding style as described in * Please obey the Linux coding style as described in
https://www.kernel.org/doc/Documentation/process/coding-style.rst with the https://www.kernel.org/doc/Documentation/process/coding-style.rst with the
following modifications and additions: following modifications and additions: