Kernel library crate for xous
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xous-kernel/src/irq.rs

50 lines
2.0 KiB

use crate::syscalls;
use crate::filled_array;
use xous_riscv::register::{mstatus, vmim};
static mut IRQ_HANDLERS: [Option<fn(usize)>; 32] = filled_array![None; 32];
pub fn handle(irqs_pending: usize) {
// Unsafe is required here because we're accessing a static
// mutable value, and it could be modified from various threads.
// However, this is fine because this is run from an IRQ context
// with interrupts disabled.
// NOTE: This will become an issue when running with multiple cores,
// so this should be protected by a mutex.
unsafe {
for irq_no in 0..IRQ_HANDLERS.len() {
if irqs_pending & (1 << irq_no) != 0 {
if let Some(f) = IRQ_HANDLERS[irq_no] {
// Call the IRQ handler
f(irq_no);
} else {
// If there is no handler, mask this interrupt
// to prevent an IRQ storm. This is considered
// an error.
vmim::write(vmim::read() | (1 << irq_no));
}
}
}
}
}
pub fn sys_interrupt_claim(irq: usize, f: fn(usize)) -> Result<(), syscalls::XousError> {
// Unsafe is required since we're accessing a static mut array.
// However, we disable interrupts to prevent contention on this array.
unsafe {
mstatus::clear_mie();
let result = if irq > IRQ_HANDLERS.len() {
Err(syscalls::XousError::InterruptNotFound)
} else if IRQ_HANDLERS[irq].is_some() {
Err(syscalls::XousError::InterruptInUse)
} else {
IRQ_HANDLERS[irq] = Some(f);
// Note that the vexriscv "IRQ Mask" register is inverse-logic --
// that is, setting a bit in the "mask" register unmasks (i.e. enables) it.
vmim::write(vmim::read() | (1 << irq));
Ok(())
};
mstatus::set_mie();
result
}
}