Discovery-migration prerequisites (M19.0)

The host bridge now carries MMIO apertures derived from the boot memory
map's gaps below 4 GiB (largest three, sort-merged; a single after-the-
last-region hole dies on OVMF's flash at the top) plus one aperture above
the described space — so a user-space device_register of PCI functions
with BAR resources can pass containment. The discovery test asserts
every PCI memory resource lies inside a bridge window and names any
escapee. device_register is idempotent on exact (parent, class, identity,
resources) match — a restarted registering bus cannot duplicate its
children; proven directly against the broker in the bus test.
ChildAdded gains device_id so a report can carry the registered kernel
id a matched driver needs as its assignment.

system/services/device-manager/device-manager-protocol.zig

@@ -73,8 +73,13 @@ pub const ChildAdded = extern struct {
     parent: u64,
     /// Where on the bus (for USB: the root port number, 1-based).
     bus_address: u64,
-    /// Bus-specific identity (for USB: the PORTSC port-speed class).
+    /// Bus-specific identity (for USB: the PORTSC port-speed class; for PCI:
+    /// the class triple).
     identity: u64,
+    /// The kernel device id this child was `device_register`ed as — what the
+    /// manager hands a matched driver as its argv assignment — or `no_device`
+    /// for an unregistered leaf (a USB port before the descriptor track).
+    device_id: u64 = no_device,
 };
 
 pub const child_added_size = @sizeOf(ChildAdded);

system/services/device-manager/device-manager.zig

@@ -136,6 +136,8 @@ const Child = struct {
     parent: u64 = 0,
     bus_address: u64 = 0,
     identity: u64 = 0,
+    // The kernel device id (registered by the reporter), or protocol.no_device.
+    device_id: u64 = 0,
     reporter: u32 = 0, // the reporting driver instance's process id
 };
 
@@ -145,18 +147,19 @@ var children: [maximum_children]Child = .{Child{}} ** maximum_children;
 /// Record (or refresh) a reported child. Refreshing matters: a restarted bus
 /// driver re-reports what it rediscovers, and the same (parent, port) must not
 /// duplicate.
-fn addChild(parent: u64, bus_address: u64, identity: u64, reporter: u32) bool {
+fn addChild(parent: u64, bus_address: u64, identity: u64, device_id: u64, reporter: u32) bool {
     var free: ?*Child = null;
     for (&children) |*child| {
         if (child.used and child.parent == parent and child.bus_address == bus_address) {
             child.identity = identity;
+            child.device_id = device_id;
             child.reporter = reporter;
             return true;
         }
         if (!child.used and free == null) free = child;
     }
     const slot = free orelse return false;
-    slot.* = .{ .used = true, .parent = parent, .bus_address = bus_address, .identity = identity, .reporter = reporter };
+    slot.* = .{ .used = true, .parent = parent, .bus_address = bus_address, .identity = identity, .device_id = device_id, .reporter = reporter };
     return true;
 }
 
@@ -382,7 +385,7 @@ fn onChildAdded(message: []const u8, reply: []u8, sender: u32) usize {
     const report = std.mem.bytesToValue(protocol.ChildAdded, message[0..protocol.child_added_size]);
     var status: i32 = 0;
     if (driverByProcess(sender)) |driver| {
-        if (!addChild(report.parent, report.bus_address, report.identity, sender)) status = -1;
+        if (!addChild(report.parent, report.bus_address, report.identity, report.device_id, sender)) status = -1;
         writeLine("device-manager: child added (device {d} port {d}, identity {d}) by {s}\n", .{ report.parent, report.bus_address, report.identity, driver.name() });
         if (status == 0) publishEvent(message[0..protocol.child_added_size]);
     } else {