0xrsydn/gameboy-rust
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feat(input): implement KEYCNT keypad interrupt control

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Add a dependency-free keypad state machine in gba-core, map KEYCNT, latch IF bit 12, and wake HALT through the existing interrupt gates. Sample complete CPU/DMA control writes once so transient byte values cannot create false requests.

Document the mGBA-style polling policy and its unverified hardware retrigger limits. Cover every button-state/selection pair, register masks, repeated requests, byte/word writes, failed-store isolation, DMA priority, ARM/Thumb IRQ return, BIOS IntrWait, and retained BIOS reset state.

Follow the restructured workspace and modular documentation. Validated on Darwin arm64: workspace and core/demo tests pass in debug and release, with Clippy, rustdoc, ten native window smoke tests, and terminal demos passing.
This commit is contained in:
0xrsydn 2026-10-05 18:00:46 +07:00
commit 597b02881b
14 changed files with 710 additions and 21 deletions
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41
crates/gba-core/src/io.rs
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@ -1,11 +1,11 @@
//! GBA I/O subset: DMA, timers, interrupts, WAITCNT, display, and polled input.
//! GBA I/O subset: DMA, timers, interrupts, WAITCNT, display, and keypad input.
//! Timer phase resets on enable or clock-source changes. Hardware startup delays,
//! shared prescaler phase, audio events, and interrupt delivery delays are not modeled.
use crate::{
display::{Display, DisplayPosition, CYCLES_PER_LINE, HBLANK_START, VISIBLE_LINES},
dma::{Dma, DmaError, Transfer, DMA_BASE, DMA_END},
input::Buttons,
input::{Buttons, Keypad},
};
pub const DISPCNT: u32 = 0x0400_0000;
@ -47,6 +47,7 @@ pub const BLDCNT: u32 = 0x0400_0050;
pub const BLDALPHA: u32 = 0x0400_0052;
pub const BLDY: u32 = 0x0400_0054;
pub const KEYINPUT: u32 = 0x0400_0130;
pub const KEYCNT: u32 = 0x0400_0132;
pub const TIMER_BASE: u32 = 0x0400_0100;
pub const IE: u32 = 0x0400_0200;
pub const IF: u32 = 0x0400_0202;
@ -137,7 +138,7 @@ pub(crate) struct Io {
effects: crate::video::effects::Effects,
window_edges: crate::video::windows::WindowEdges,
horizontal_windows: crate::video::windows::horizontal::HorizontalWindows,
buttons: Buttons,
keypad: Keypad,
display: Display,
dma: Dma,
postflg: bool,
@ -146,7 +147,7 @@ pub(crate) struct Io {
impl Io {
pub(crate) fn mapped(address: u32) -> bool {
matches!(address, 0x0400_0000..=0x0400_0057 | DMA_BASE..=DMA_END | 0x0400_0100..=0x0400_010f | 0x0400_0130..=0x0400_0131 | 0x0400_0200..=0x0400_020b | POSTFLG..=0x0400_0303)
matches!(address, 0x0400_0000..=0x0400_0057 | DMA_BASE..=DMA_END | 0x0400_0100..=0x0400_010f | 0x0400_0130..=0x0400_0133 | 0x0400_0200..=0x0400_020b | POSTFLG..=0x0400_0303)
}
pub(crate) fn read8(&self, address: u32) -> Option<u8> {
@ -165,7 +166,8 @@ impl Io {
WINOUT => self.effects.outside,
BLDCNT => self.effects.control,
BLDALPHA => self.effects.alpha,
KEYINPUT => self.buttons.keyinput(),
KEYINPUT => self.keypad.keyinput(),
KEYCNT => self.keypad.control(),
0x0400_0100..=0x0400_010e => {
let timer = &self.timers[((address - TIMER_BASE) / 4) as usize];
if address & 2 == 0 {
@ -188,8 +190,10 @@ impl Io {
}
/// The memory bus validates every byte before calling this method.
/// Keypad accesses use write_keypad instead, preserving transfer boundaries.
pub(crate) fn write8(&mut self, address: u32, value: u8) {
debug_assert!(Self::mapped(address));
debug_assert!(!(KEYINPUT..=KEYCNT + 1).contains(&address));
if (DMA_BASE..=DMA_END).contains(&address) {
self.dma.write8(address, value);
return;
@ -198,7 +202,7 @@ impl Io {
DISPCNT => self.dispcnt = replace_byte(self.dispcnt, address, value) & 0xfff7,
GREENSWAP if address & 1 == 0 => self.greenswap = value & 1 != 0,
DISPSTAT => self.pending |= self.display.write_status(address & 1 != 0, value),
VCOUNT | KEYINPUT => {} // Read-only; writes are ignored.
VCOUNT => {} // Read-only; writes are ignored.
BG0CNT..=BG3CNT => {
let index = ((address - BG0CNT) / 2) as usize;
let control = &mut self.backgrounds[index].control;
@ -294,7 +298,30 @@ impl Io {
}
pub(crate) fn set_buttons(&mut self, buttons: Buttons) {
self.buttons = buttons;
if self.keypad.set_buttons(buttons) {
self.pending |= 1 << 12;
}
self.wake_if_requested();
}
/// Commit one validated byte/halfword/word access in the keypad block.
/// KEYINPUT writes are ignored. Sample once after both KEYCNT bytes merge,
/// never on a transient low-byte value during a halfword or word write.
pub(crate) fn write_keypad(&mut self, address: u32, bytes: &[u8]) {
debug_assert!(address >= KEYINPUT && address + bytes.len() as u32 <= KEYCNT + 2);
let mut control = self.keypad.control();
let mut touched = false;
for (offset, byte) in bytes.iter().enumerate() {
let address = address + offset as u32;
if (KEYCNT..=KEYCNT + 1).contains(&address) {
control = replace_byte(control, address, *byte);
touched = true;
}
}
if touched && self.keypad.write_control(control) {
self.pending |= 1 << 12;
}
self.wake_if_requested();
}
pub(crate) fn display_control(&self) -> u16 {