Wire real PS/2 mouse packets through to input events

Replace the mouse driver's synthetic stream with the real path, the
way the keyboard was wired:

- The auxiliary port's IRQ12 is enumerated on the mouse's own ACPI
  node (PNP0F13), and the kernel only lets a device's claimer bind or
  ack its IRQs — so ps2-bus now claims that node alongside the
  controller whenever port 2 carries a device, binds IRQ12 to its one
  endpoint, and re-arms whichever line the notification's badge names.
  The forwarding loop already routed auxiliary bytes by status bit 5.
- mouse-packet.zig (new, pure, host-tested): three-byte stream-mode
  packet assembly — bit-3 sync with resynchronization, ACK/BAT bytes
  dropped at packet start, nine-bit two's-complement movement,
  overflow packets discarded, and PS/2 positive-Y-up converted to the
  screen convention (positive down).
- mouse.zig mirrors the keyboard driver: no hardware claim, attaches
  to the bus as its mouse, and publishes button_down/button_up per
  changed button plus motion events with the pressed-button mask.

Verified end to end in QEMU via monitor mouse_move/mouse_button:
motion round-trips in screen coordinates, buttons transition with the
right mask, and keyboard events keep flowing alongside. The follow-up
is the IntelliMouse magic-knock for a scroll wheel (four-byte packets)
and scroll events.

build.zig

@@ -511,6 +511,7 @@ pub fn build(b: *std.Build) void {
         "system/devices/acpi-ids.zig", // _HID name decoding
         "library/mmio/mmio.zig", // barriers assemble + registers round-trip
         "system/drivers/ps2-bus/scancode.zig", // set-2 decode + keyboard state machine
+        "system/drivers/ps2-bus/mouse-packet.zig", // 3-byte mouse packet assembly
     }) |root| {
         const mod_tests = b.addTest(.{
             .root_module = b.createModule(.{

docs/input.md

@@ -126,11 +126,18 @@ the service delivers to its endpoint, which only the same thread could receive).
   control characters for Enter/Tab/Backspace/Escape, whose keysyms map to no Unicode. The
   layout defaults to `us`; the bus can pass another as the driver's argv[2] — the seam for
   a future settings source.
-- **The mouse is still synthetic.** [mouse.zig](../system/drivers/ps2-bus/mouse.zig)
+- **The mouse is real too.** IRQ12 is enumerated on the auxiliary device's own ACPI node
-  publishes a placeholder motion/click stream; the hardware-free `input-source` likewise
+  (PNP0F13), so the bus claims that node alongside the controller and routes both IRQs to
-  rotates through all three classes (including a synthetic joystick, which has no driver
+  its one endpoint, acking whichever line the notification's badge names.
-  yet) via the `input.synthetic*Event` helpers. **Follow-up:** the mouse driver attaches to
+  [mouse.zig](../system/drivers/ps2-bus/mouse.zig) attaches the way the keyboard does and
-  the bus the way the keyboard does and decodes 3/4-byte packets into mouse events.
+  assembles the forwarded bytes with
+  [mouse-packet.zig](../system/drivers/ps2-bus/mouse-packet.zig) (three-byte stream-mode
+  packets: sync/overflow handling, nine-bit movement, screen-convention `dy` — host-tested
+  under `zig build test`) into `button_down`/`button_up` transitions and `motion` events.
+  **Follow-up:** the IntelliMouse magic-knock for a scroll wheel (four-byte packets) and
+  `scroll` events. The hardware-free `input-source` still rotates through all three classes
+  synthetically (including a joystick, which has no driver yet) via the
+  `input.synthetic*Event` helpers.
 - **Drop-oldest under overflow** is a defined loss; the 16-slot ring absorbs normal bursts.
   Real backpressure/flow-control is future work.
 - **`publish` is unauthenticated** — any process may publish, consistent with the current

system/drivers/ps2-bus/mouse-packet.zig

@@ -0,0 +1,143 @@
+//! PS/2 mouse packet assembly — the byte stream a streaming mouse sends, turned
+//! into decoded movement/button reports.
+//!
+//! A standard PS/2 mouse in stream mode sends three-byte packets:
+//!
+//!   byte 0: | Y ovf | X ovf | Y sign | X sign | 1 | middle | right | left |
+//!   byte 1: X movement (low eight bits; the sign bit lives in byte 0)
+//!   byte 2: Y movement (likewise)
+//!
+//! Movement is nine-bit two's complement, PS/2 convention: positive X right,
+//! positive Y **up**. The decoded packet converts Y to the screen convention
+//! (positive down), matching what every consumer of relative motion expects.
+//! Bit 3 of byte 0 is always set — the resynchronization anchor: a byte at
+//! packet start with bit 3 clear cannot be a packet header and is dropped.
+//!
+//! Everything here is pure (no imports beyond `std`, no IO), so it is
+//! host-testable: the tests at the bottom run under `zig build test`.
+
+const std = @import("std");
+
+/// One decoded movement/button report, in screen convention (positive dy down).
+pub const Packet = struct {
+    left: bool,
+    right: bool,
+    middle: bool,
+    dx: i16,
+    dy: i16,
+};
+
+const header_always_set: u8 = 1 << 3;
+const header_left: u8 = 1 << 0;
+const header_right: u8 = 1 << 1;
+const header_middle: u8 = 1 << 2;
+const header_x_sign: u8 = 1 << 4;
+const header_y_sign: u8 = 1 << 5;
+const header_x_overflow: u8 = 1 << 6;
+const header_y_overflow: u8 = 1 << 7;
+
+/// Device protocol bytes that can reach the packet stream around bring-up (the
+/// acknowledge to enable-reporting, a reset's self-test result). Both have bit 3
+/// set, so the header check alone cannot reject them; they are recognized only
+/// at packet start, where a real header cannot be one of them in practice.
+const response_acknowledge: u8 = 0xFA;
+const response_self_test_passed: u8 = 0xAA;
+
+/// Accumulates the byte stream into `Packet`s. Feed it every byte the mouse
+/// sends; the third byte of each well-formed packet returns one.
+pub const Assembler = struct {
+    bytes: [3]u8 = undefined,
+    count: u8 = 0,
+
+    pub fn feed(self: *Assembler, byte: u8) ?Packet {
+        if (self.count == 0) {
+            // Resynchronize: a packet must start with a plausible header.
+            if (byte & header_always_set == 0) return null;
+            if (byte == response_acknowledge or byte == response_self_test_passed) return null;
+        }
+        self.bytes[self.count] = byte;
+        self.count += 1;
+        if (self.count < 3) return null;
+        self.count = 0;
+
+        const header = self.bytes[0];
+        // An overflowed count is garbage by definition; discard the packet.
+        if (header & (header_x_overflow | header_y_overflow) != 0) return null;
+
+        return .{
+            .left = header & header_left != 0,
+            .right = header & header_right != 0,
+            .middle = header & header_middle != 0,
+            .dx = movement(self.bytes[1], header & header_x_sign != 0),
+            // PS/2 positive Y is up; screen positive Y is down.
+            .dy = -movement(self.bytes[2], header & header_y_sign != 0),
+        };
+    }
+
+    /// Nine-bit two's complement: the eight movement bits plus the header's sign.
+    fn movement(low: u8, negative: bool) i16 {
+        const value: i16 = low;
+        return if (negative) value - 256 else value;
+    }
+};
+
+// --- tests (host-run via `zig build test`) ------------------------------------
+
+const testing = std.testing;
+
+fn feedAll(assembler: *Assembler, bytes: []const u8) ?Packet {
+    var result: ?Packet = null;
+    for (bytes) |byte| {
+        if (assembler.feed(byte)) |packet| result = packet;
+    }
+    return result;
+}
+
+test "plain motion decodes with screen-convention y" {
+    var assembler = Assembler{};
+    const packet = feedAll(&assembler, &.{ 0x08, 5, 3 }).?;
+    try testing.expectEqual(@as(i16, 5), packet.dx);
+    try testing.expectEqual(@as(i16, -3), packet.dy); // PS/2 up 3 -> screen -3
+    try testing.expect(!packet.left and !packet.right and !packet.middle);
+}
+
+test "negative movement sign-extends through the header bits" {
+    var assembler = Assembler{};
+    // X sign and Y sign set: dx = 0xFB - 256 = -5, dy raw = 0xFE - 256 = -2 -> screen +2.
+    const packet = feedAll(&assembler, &.{ 0x08 | 0x10 | 0x20, 0xFB, 0xFE }).?;
+    try testing.expectEqual(@as(i16, -5), packet.dx);
+    try testing.expectEqual(@as(i16, 2), packet.dy);
+}
+
+test "buttons decode from the header" {
+    var assembler = Assembler{};
+    const packet = feedAll(&assembler, &.{ 0x08 | 0x01 | 0x02, 0, 0 }).?;
+    try testing.expect(packet.left);
+    try testing.expect(packet.right);
+    try testing.expect(!packet.middle);
+}
+
+test "a byte with bit 3 clear at packet start is dropped" {
+    var assembler = Assembler{};
+    // The stray 0x02 cannot be a header; the following packet still decodes.
+    try testing.expectEqual(@as(?Packet, null), assembler.feed(0x02));
+    const packet = feedAll(&assembler, &.{ 0x09, 1, 0 }).?;
+    try testing.expect(packet.left);
+    try testing.expectEqual(@as(i16, 1), packet.dx);
+}
+
+test "protocol bytes at packet start are dropped" {
+    var assembler = Assembler{};
+    try testing.expectEqual(@as(?Packet, null), assembler.feed(0xFA)); // enable-reporting ACK
+    try testing.expectEqual(@as(?Packet, null), assembler.feed(0xAA)); // self-test passed
+    const packet = feedAll(&assembler, &.{ 0x08, 7, 0 }).?;
+    try testing.expectEqual(@as(i16, 7), packet.dx);
+}
+
+test "an overflowed packet is discarded whole" {
+    var assembler = Assembler{};
+    try testing.expectEqual(@as(?Packet, null), feedAll(&assembler, &.{ 0x08 | 0x40, 0xFF, 0xFF }));
+    // The assembler is back at packet start.
+    const packet = feedAll(&assembler, &.{ 0x08, 1, 1 }).?;
+    try testing.expectEqual(@as(i16, 1), packet.dx);
+}

system/drivers/ps2-bus/mouse.zig

@@ -1,19 +1,52 @@
 //! PS/2 Mouse Driver
 //!
-//! Spawned by the ps2-bus driver once the controller is initialized and port 2
+//! Spawned by the ps2-bus driver once the controller is initialized and the port
 //! has passed its interface test and device reset. The bus driver hands us our
-//! device HID as argv[1]; we use it to locate our own device descriptor.
+//! device HID as argv[1].
+//!
+//! Like the keyboard, this driver never touches the hardware: the 8042's ports
+//! and both port IRQs are owned by the ps2-bus driver (the auxiliary port's
+//! IRQ12 lives on the PNP0F13 node, which the bus claims alongside the
+//! controller). The driver **attaches** to the bus and receives every byte the
+//! mouse sends as a forwarded asynchronous message. The bytes assemble into
+//! three-byte packets, and each packet becomes input-protocol events:
+//!
+//!   packet -> button transitions -> button_down / button_up
+//!          -> movement            -> motion (dx/dy, screen convention)
 
 const std = @import("std");
 const runtime = @import("runtime");
 const ps2 = @import("ps2-library.zig");
+const mouse_packet = @import("mouse-packet.zig");
 const device = runtime.device;
+const ipc = runtime.ipc;
+const protocol = runtime.input_protocol;
 
 fn writeLine(comptime fmt: []const u8, arguments: anytype) void {
     var line: [128]u8 = undefined;
     _ = runtime.system.write(std.fmt.bufPrint(&line, fmt, arguments) catch return);
 }
 
+/// Look up the ps2-bus service, retrying while the bus (which spawned us before
+/// registering) is still coming up.
+fn lookupBus() ?ipc.Handle {
+    var attempts: usize = 0;
+    while (attempts < 100) : (attempts += 1) {
+        if (ipc.lookup(.ps2_bus)) |handle| return handle;
+        runtime.system.sleep(50);
+    }
+    return null;
+}
+
+/// The protocol's pressed-button bitmask for a packet.
+fn buttonMask(packet: mouse_packet.Packet) u32 {
+    var mask: u32 = 0;
+    if (packet.left) mask |= protocol.mouse_button_left;
+    if (packet.right) mask |= protocol.mouse_button_right;
+    if (packet.middle) mask |= protocol.mouse_button_middle;
+    return mask;
+}
+
 pub fn main(init: runtime.process.Init) void {
     const hid = init.arguments.get(1).?;
 
@@ -27,34 +60,81 @@ pub fn main(init: runtime.process.Init) void {
         _ = runtime.system.write("system/drivers/ps2-bus/mouse: out of memory\n");
         return;
     };
-    const mouse_device_descriptor = device.findDeviceDescriptorByHid(buffer, hid) orelse {
+    if (device.findDeviceDescriptorByHid(buffer, hid) == null) {
         writeLine("system/drivers/ps2-bus/mouse: no device for hid {s}\n", .{hid});
         return;
-    };
+    }
 
-    // The mouse's own node (PNP0F13) carries IRQ12 and is not claimed by the bus,
+    // Attach to the bus: hand it our endpoint, and it forwards every byte the
-    // so this driver takes exclusive ownership of it. Port IO still goes through
+    // mouse sends (it owns the controller; we own the decoding).
-    // the bus, which owns the shared 8042 ports.
+    const bus = lookupBus() orelse {
-    if (!device.claim(mouse_device_descriptor.id)) {
+        _ = runtime.system.write("system/drivers/ps2-bus/mouse: ps2-bus service unavailable\n");
-        writeLine("system/drivers/ps2-bus/mouse: unable to claim device for hid {s}\n", .{hid});
+        return;
+    };
+    const endpoint = ipc.createIpcEndpoint() orelse {
+        _ = runtime.system.write("system/drivers/ps2-bus/mouse: no endpoint\n");
+        return;
+    };
+    var attach = ps2.AttachRequest{ .device_type = @intFromEnum(ps2.DeviceType.mouse) };
+    var attach_reply: [@sizeOf(ps2.AttachReply)]u8 = undefined;
+    const attached = ipc.callCap(bus, std.mem.asBytes(&attach), &attach_reply, endpoint) catch {
+        _ = runtime.system.write("system/drivers/ps2-bus/mouse: attach call failed\n");
+        return;
+    };
+    if (attached.len < @sizeOf(ps2.AttachReply) or
+        std.mem.bytesToValue(ps2.AttachReply, attach_reply[0..@sizeOf(ps2.AttachReply)]).status != 0)
+    {
+        _ = runtime.system.write("system/drivers/ps2-bus/mouse: attach refused\n");
         return;
     }
-    writeLine("system/drivers/ps2-bus/mouse: claimed device for hid {s}\n", .{hid});
 
-    // Broadcast mouse events through the input service so programs can listen for them
+    // Broadcast mouse events through the input service so programs can listen
-    // (docs/input.md). As with the keyboard, decoding real PS/2 mouse packets is a
+    // for them (docs/input.md).
-    // follow-up; for now we publish the synthetic stand-in stream. The fan-out path is
-    // real, only the source of the movement is placeholder.
     var source = runtime.input.connectSource() orelse {
         _ = runtime.system.write("system/drivers/ps2-bus/mouse: input service unavailable\n");
         return;
     };
     _ = runtime.system.write("system/drivers/ps2-bus/mouse: ok\n");
 
-    var step: usize = 0;
+    var assembler = mouse_packet.Assembler{};
-    while (true) : (step +%= 1) {
+    var buttons: u32 = 0;
-        _ = source.publishMouseEvent(runtime.input.syntheticMouseEvent(step));
+    var receive: [@sizeOf(ps2.ForwardedByte)]u8 = undefined;
-        runtime.system.sleep(200);
+    while (true) {
+        const got = ipc.replyWait(endpoint, &.{}, &receive, null);
+        if (!got.isMessage() or got.len < @sizeOf(ps2.ForwardedByte)) continue;
+        const forwarded = std.mem.bytesToValue(ps2.ForwardedByte, receive[0..@sizeOf(ps2.ForwardedByte)]);
+
+        const packet = assembler.feed(@intCast(forwarded.byte & 0xFF)) orelse continue;
+        const new_buttons = buttonMask(packet);
+
+        // A button transition per changed button, carrying the new whole mask.
+        const changed = buttons ^ new_buttons;
+        for ([_]u32{ protocol.mouse_button_left, protocol.mouse_button_right, protocol.mouse_button_middle }) |button| {
+            if (changed & button == 0) continue;
+            const kind: protocol.MouseEventKind = if (new_buttons & button != 0) .button_down else .button_up;
+            _ = source.publishMouseEvent(.{
+                .kind = @intFromEnum(kind),
+                .button = button,
+                .dx = 0,
+                .dy = 0,
+                .scroll_x = 0,
+                .scroll_y = 0,
+                .buttons = new_buttons,
+            });
+        }
+        buttons = new_buttons;
+
+        if (packet.dx != 0 or packet.dy != 0) {
+            _ = source.publishMouseEvent(.{
+                .kind = @intFromEnum(protocol.MouseEventKind.motion),
+                .button = 0,
+                .dx = packet.dx,
+                .dy = packet.dy,
+                .scroll_x = 0,
+                .scroll_y = 0,
+                .buttons = new_buttons,
+            });
+        }
     }
 }
 

system/drivers/ps2-bus/ps2-bus.zig

@@ -229,19 +229,41 @@ pub fn main() void {
     }
 
     // From here on, only the interrupt path reads the data port. Drop anything a
-    // device sent between enable-scanning and now, bind the IRQ, and only then
+    // device sent between enable-scanning and now, bind the IRQs, and only then
-    // let the controller raise it — an interrupt with nobody bound is lost.
+    // let the controller raise them — an interrupt with nobody bound is lost.
     controller.drainOutputBuffer();
     if (!device.irqBind(controller.device_id, interrupt_index, endpoint)) {
         _ = runtime.system.write("system/drivers/ps2-bus: irq_bind failed\n");
         return;
     }
+
+    // Port 2's interrupt (IRQ12) is enumerated on the auxiliary device's own ACPI
+    // node (PNP0F13), not on the controller's — so if port 2 carries a device,
+    // claim that node too and route its IRQ to the same endpoint. The IRQ belongs
+    // to the *port*, whatever device identify found on it.
+    var maybe_auxiliary_interrupt: ?struct { device_id: u64, interrupt_index: u64, gsi: u64 } = null;
+    if (port_device_types[@intFromEnum(ps2.Port.Two)] != null) {
+        if (device.findDeviceDescriptorByHid(buffer, "PNP0F13")) |descriptor| {
+            if (findInterruptResourceIndex(descriptor)) |auxiliary_index| {
+                if (device.claim(descriptor.id) and device.irqBind(descriptor.id, auxiliary_index, endpoint)) {
+                    maybe_auxiliary_interrupt = .{
+                        .device_id = descriptor.id,
+                        .interrupt_index = auxiliary_index,
+                        .gsi = descriptor.resources[auxiliary_index].start,
+                    };
+                } else {
+                    _ = runtime.system.write("system/drivers/ps2-bus: auxiliary irq_bind failed\n");
+                }
+            }
+        }
+    }
+
     var configuration = controller.readConfigurationByte() orelse {
         _ = runtime.system.write("system/drivers/ps2-bus: controller configuration timed out\n");
         return;
     };
     if (port_device_types[@intFromEnum(ps2.Port.One)] != null) configuration |= ps2.Port.One.interruptBit();
-    if (port_device_types[@intFromEnum(ps2.Port.Two)] != null) configuration |= ps2.Port.Two.interruptBit();
+    if (maybe_auxiliary_interrupt != null) configuration |= ps2.Port.Two.interruptBit();
     _ = controller.writeConfigurationByte(configuration);
 
     _ = runtime.system.write("system/drivers/ps2-bus: ok\n");
@@ -269,7 +291,17 @@ pub fn main() void {
                 // An unattached port's byte is dropped — e.g. a keystroke before
                 // the keyboard driver has attached.
             }
-            _ = device.irqAck(controller.device_id, interrupt_index);
+            // Re-arm the line that woke us: the notification badge carries the
+            // GSI, and IRQ1 and IRQ12 are acked through different device claims.
+            if (maybe_auxiliary_interrupt) |auxiliary| {
+                if (got.source() == auxiliary.gsi) {
+                    _ = device.irqAck(auxiliary.device_id, auxiliary.interrupt_index);
+                } else {
+                    _ = device.irqAck(controller.device_id, interrupt_index);
+                }
+            } else {
+                _ = device.irqAck(controller.device_id, interrupt_index);
+            }
             continue;
         }
         reply_len = handleAttach(receive[0..got.len], got, &reply_buffer);