hx20: Fn key rollover can trigger incorrect break codes, resulting in infinite key repeat

[DHowett]

The easiest way I've found to reproduce this is by:

1. Pressing Vol Down
2. Pressing Vol Up
3. Releasing Vol Down

If done properly, releasing Vol Up will result in a break code for F3 being generated. This can also be accomplished with some combination of Fn and the arrow/page keys.

It appears that the state-tracking variables keep_fn_* aren't transitioning through their state graph correctly.

https://github.com/FrameworkComputer/EmbeddedController/blob/8109392adb17a2cd7d30a74eee8613a0cb72ee7d/board/hx20/keyboard_customization.c#L238-L240

Step	Action	Call	Final State
1	Press Vol Down	hotkey_F1_F12(&0x0006, 0, 1)	keep_fn_key_F1F12 == 1 Set to 1 because the key was pressed
2	Press Vol Up	hotkey_F1_F12(&0x0004, 0, 1)	keep_fn_key_F1F12 == 1 Set to 1 because the key was pressed
3	Release Vol Down	hotkey_F1_F12(&0x0006, 0, 0)	keep_fn_key_F1F12 == 0 Cleared because the key was released
4	Release Vol Up	hotkey_F1_F12(&0x0004, 0, 0)	keep_fn_key_F1F12 == 0 We exit early (see code below) because this is 0

https://github.com/FrameworkComputer/EmbeddedController/blob/8109392adb17a2cd7d30a74eee8613a0cb72ee7d/board/hx20/keyboard_customization.c#L296-L297

[kiram9]

@DHowett see https://github.com/FrameworkComputer/EmbeddedController/commit/fa8982056aa0ad6267029cf3ea20dc5c59cba282

[DHowett]

Ah, that looks perfect!

[DHowett]

Yep, confirming fixed as of 9450caa