This removes level-triggered interrupts.
While working on https://github.com/tinygo-org/tinygo/pull/3170, I found
these level triggered interrupt constants. Apart from them being
inconsistent with each other (PinLowLevel vs PinLevelLow) I don't think
they are actually used anywhere. In addition, I removed the
PinNoInterrupt constant on the esp32c3. This makes the esp32c3 pass the
tests in #3170.
I looked into level-triggered interrupts and I really couldn't find a
good justification for them:
- They were added to the esp32c3 and the rp2040 together with other
pin interrupt types, meaning they were probably just added because
the chip supports the feature and not because they were actually
needed.
- Level interrupts aren't supported in TinyGo for any other chip, and
I haven't seen anybody ask for this feature.
- They aren't supported in the nrf series chips _at all_, and with a
quick search I found only very little demand for them in general.
- I tried to see whether there is any good use case for them, but I
couldn't really find one (where an edge triggered interrupt wouldn't
work just as well). If there is one where level triggered interrupts
are a real advantage over edge triggered interrupts, please let me
know.
Of course, we shouldn't remove a feature lightly. But in this case, I
can't think of an advantage of having this feature. I can think of
downsides: more maintenance and having to specify their behavior in the
machine package documentation.
In general, I would like to keep the machine package clean and only
support things that have a proven use case.
Some targets used capital PullUp/PullDown, while the documented standard
is Pullup/Pulldown. This commit fixes this mismatch, while preserving
compatibility with aliases that are marked deprecated.
Go 1.19 started reformatting code in a way that makes it more obvious
how it will be rendered on pkg.go.dev. It gets it almost right, but not
entirely. Therefore, I had to modify some of the comments so that they
are formatted correctly.
Do it all at once in preparation for Go 1.18 support.
To make this commit, I've simply modified the `fmt-check` Makefile
target to rewrite files instead of listing the differences. So this is a
fully mechanical change, it should not have introduced any errors.
It is always implemented exactly the same way (as an uint8) so there is
no reason to implement it in each target separately.
This also makes it easier to add some documentation to it.
