FlexIO module naming consistency for 1011, 1021

[mciantyre]

Since the 1011 and 1021 MCUs only have one FlexIO peripheral instance, the RAL generation pipeline names the module as flexio1.

imxrt-ral/src/imxrt1011.rs

Line 704 in 0b0d968

pub mod flexio1 {

This prevents us from using a consistent module path in Rust code. See the (current) build status of imxrt-rs/imxrt-hal#139 for an example of an issue that manifests when names aren't consistent.

Use renaming techniques (SVD patches, raltool transforms) to rename flexio1 to flexio in 1011 and 1021 MCUs.

[mciantyre]

Here's how this was solved for ADC and PWM peripherals on the 1011. Something similar should still work for FlexIO.

imxrt-ral/devices/imxrt1011.yaml

Lines 17 to 30 in 0b0d968

	# Rename ADC1 => ADC to keep module names consistent
	# across chips:
	#
	# // Before
	# use imxrt_ral::adc1;
	# // After
	# use imxrt_ral::adc;
	#
	# Same for PWM.
	_modify:
	ADC1:
	name: ADC
	PWM1:
	name: PWM

[Finomnis]

This is a breaking change, though, so it will require a major version bump. Although you are probably aware.

[mciantyre]

I haven't tried anything yet, but I think there's a backwards-compatible approach. After correcting the module name, I'll create a 0.5 release branch. Then, I'll manually add modules for the old name, something like

#[deprecated(since = "0.5.1", note = "Use the 'flexio' module instead of this module")]
pub mod flexio1 {
  pub use super::flexio::*;
}

If that all works, we could release that in 0.5.1 for immediate use in the HAL. I assume the maintainer burden to keep the patches for the rest of the 0.5 release. A commit with some smoke tests could help us make sure this all works, and help me with any longer-term maintenance.

---

The path imxrt_ral::flexio::FLEXIO, without the '1' on FLEXIO, is consistent with the way the ADC instance types and pointer items are generated after the 1011 module rename. The ADC instance types / pointer item is just ADC, not ADC1. (Good eye; this would play into the aliasing idea.)

Specific to the clock gate routines, the HAL handles this with a branch that checks for the "sole instance" const generic. Here's the ADC clock gate implementation.

[Finomnis]

@mciantyre I added the first part of your suggestion. If you volunteer to provide the 0.5.1, then I feel like this is all set :)

[Finomnis]

I also added a namespace existence smoke test in that PR.

[Finomnis]

@mciantyre Any feedback on this? What's missing?