docs/utime: Explicitly describe that ticks_ms(), etc. return small int.
I.e. never allocate memory.
@@ -78,7 +78,8 @@ Functions
.. function:: ticks_ms()
Returns an increasing millisecond counter with an arbitrary reference point, that
- wraps around after some value.
+ wraps around after some value. The returned value is guaranteed to be a `small integer`,
+ i.e. this function works without memory allocation.
The wrap-around value is not explicitly exposed, but we will
refer to it as *TICKS_MAX* to simplify discussion. Period of the values is
@@ -99,7 +100,8 @@ Functions
.. function:: ticks_us()
- Just like `ticks_ms()` above, but in microseconds.
+ Just like `ticks_ms()` above, but in microseconds. The returned value is
+ guaranteed to be a `small integer`.
.. function:: ticks_cpu()
@@ -112,6 +114,8 @@ Functions
function is intended for very fine benchmarking or very tight real-time loops.
Avoid using it in portable code.
+ The returned value is guaranteed to be a `small integer`.
+
Availability: Not every port implements this function.
