Two driver-model milestones plus a tree-wide naming pass. Suite 35/35
(QEMU) + host tests green.
M11 — IRQ-as-IPC. A ring-3 driver now sleeps until its device interrupts
it. New src/kernel/irq.zig: per-GSI endpoint bindings, comptime per-vector
trampolines, dispatch = mask GSI -> LAPIC EOI -> notifyLocked, all under one
lock region. irq_bind/irq_ack syscalls, gated by the device claim like
mmio_map. interruptDispatch no longer EOIs — each handler owns its EOI,
because a level line must be masked before it is acknowledged (irq_ack is
the unmask). Bindings are keyed on the owning task and released on exit
(a shared endpoint's siblings survive). hpetd rewritten interrupt-driven.
Tests: hpet (rewritten, reads back the I/O APIC routing) and irqfree.
M12 — bus drivers. DeviceDesc gains a parent, making the device table a
tree. dev_register (device_register) lets a process publish children below
a device it claimed; the kernel enforces resource containment (a child's
resources must nest in its parent's), so a descriptor can't fabricate a
window over kernel RAM. Descriptor copied in via copyFromUser (physmap
walk — an unmapped user pointer fails the call instead of faulting the
kernel). Per-parent child cap bounds table exhaustion. sbin/busd.zig is a
worked bus driver. Test: bus.
Naming — per docs/coding-standards.md: non-acronym abbreviations spelled
out (message, descriptor, device_service, scheduler, runtime, physical,
interpreter, ...); acronyms kept (IPC, MMIO, DMA, HCD, ...); files are
kebab-case (ipc-synchronous.zig, device-service.zig, vfs-protocol.zig, ...).
Exceptions: POSIX/C ABI names and Zig idioms (init/len/ptr) kept. Module
collisions resolved by specific naming (config -> parameters, device.zig
alias -> device_model). AML op/Op disambiguated: op = opcode, Op =
operation; per-opcode parse handlers renamed opX -> parseX.
New driver docs: drivers.md, driver-model.md (bus/class/HCD shapes + the
proposed M13–M16 ABI), coding-standards.md.
A user-space process can now touch real hardware directly, capability-gated by
the device tree — the microkernel driver model.
- src/kernel/devsvc.zig: flattens the discovered device tree into an
id-indexed snapshot + a claim table at boot (devsvc.init from main.zig).
- Syscalls 11-13: dev_enumerate (snapshot the table), dev_claim (take
exclusive ownership), mmio_map (map a claimed device's MMIO window into the
caller's AS and return the register base). The claim is the capability:
mmio_map refuses any device the caller doesn't own.
- paging.mapUserDeviceInto: maps device MMIO strong-uncacheable (PCD|PWT) and
marks each leaf with a device_grant PTE bit; freeSubtree skips pmm.free on
those leaves, so tearing down a driver never returns MMIO frames to the RAM
pool (the teardown hazard). MMIO grants live in a distinct arena, PML4[226]
(Task.dev_map_next), so device pages widen no kernel mapping.
- lib/dev.zig: user enumerate/claim/mmioMap wrappers; shared DeviceDesc/ResDesc
in danos (root.zig). sbin/hpetd.zig: finds the HPET, claims it, maps its
registers, enables the counter (an MMIO write) and reads it (0xF0) — proving
read+write passthrough to real hardware.
- Tests: `hpet` (driver reads the counter advancing from ring 3) and `iopass`
(device-granted frame survives address-space teardown). Suite 33/33.
irq_bind/irq_ack (IRQ-as-message) are stubbed (-1) pending; notifyFromIsr (M7)
is the hook they'll use.
Daniel Samson