1376: rtc: cleanup and consolidate r=Dirbaio a=xoviat
This removes an extra file that I left in, adds an example, and consolidates the files into one 'v2' file.
Co-authored-by: xoviat <xoviat@users.noreply.github.com>
inline assembly is supported since rust 1.59, we're way past that.
enabling this makes the compiled code more compact, and on rp2040
even decreses memory usage by not needing thunks in sram.
This introduces a `Pender` struct with enum cases for thread-mode, interrupt-mode and
custom callback executors. This avoids calls through function pointers when using only
the thread or interrupt executors. Faster, and friendlier to `cargo-call-stack`.
`embassy-executor` now has `arch-xxx` Cargo features to select the arch and to enable
the builtin executors (thread and interrupt).
It currently contains whoever was first to write some code for the crate,
even if many more people have contributed to it later.
The field is "sort of" deprecated, it was made optional recently:
https://rust-lang.github.io/rfcs/3052-optional-authors-field.html
Due the the reasons listed there I believe removing it is better than
setting it to generic fluff like "The Embassy contributors".
The replacement is `embassy-usb`. There's a WIP driver for stm32 USBD in #709,
there's no WIP driver for stm32 USB_OTG. This means we're left without
USB_OTG support for now.
Reason for removing is I'm going to soon remove `embassy::io`, and
USB uses it. I don't want to spend time maintaining "dead" code
that is going to be removed. Volunteers welcome, either to update
old USB to the new IO, or write a USB_OTG driver fo the new USB.
