[preview] new joypad library does not work on iQue

[rasky]

The new joypad library is completely non functional on iQue. We have been reported that this is because iQue sports a limited hardware emulator of the PIF chip that only knows how to parse a subset of valid joybus commands.

This is a quote apparently by Zoinkity:

Did get the N64 test cart rom to boot on an ique to verify the RCP works identically. One quirk it has is
it doesn't use libultra controller functions and iQue doesn't appear to parse the bytecode correctly
(or at all, it could pattern-match like some emulators did).
OxFF is a NOP, used to align other commands to make them easier to read out or place them at
predictable addresses. They aren't necessary and the test cart doesn't write them (it keeps pointers
instead). However, iQue ignores commands if they don't contain the normal padding libultra adds in.
Utterly maddening to figure out.
Controller input reads are PIF command 1:
01 04 01 --------
iQue will only respond to it if it's preceded by a NOP:
FF 01 04 01 -------
Not sure if that breaks any common homebrew code. It might not seem like much, but if the iQue
can't forward commands that limits what will work or if slot devices can be used with/as attached
MP controllers.

The above would also apply to the new joypad library that doesn't put the FF padding.

[rasky]

Basic controller input works on iQue now (de5b8a0). There are still two possible issues:

• Inspector does not work (it uses a different codepath)
• Only the first controller is detected. This is a confirmed regression from trunk, though we have no clue at the moment.