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library: the last three protocols speak the envelope

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These were the awkward ones. Each began with an operation packed into a
single byte — two of them with a version wedged in beside it — so there was
no wrapping them: the layouts had to be rebuilt. The device manager's own
enumerate and subscribe become the reserved verbs that mean the same thing
everywhere, its replies lose three status structs the envelope already
carries, and a device id becomes the packet's target. Power drops the
version it repeated on every request, because describe is the handshake,
and stops claiming a 64-byte ceiling it never needed for calls. USB moves a
control transfer's data to the packet tail in both directions, which makes
the status length the transferred length and retires a field that had been
saying the same thing twice.

The danger in this one was not the protocols but their readers. Init
recognised a power button by two bytes at the head of a message, the ACPI
service dispatched on the first byte, the xHCI driver read its operation
with a raw integer load, and the HID drivers reinterpreted a report
wholesale — none of which would have failed to compile once the layouts
moved. They would simply have stopped: no shutdown on the power button, no
reports from the keyboard. Every one of them now reads through the
generated types, and the shutdown gate that answers only a subscriber is
the same code it was.

Two sizes were decided by measuring rather than assuming. The child-added
message is both a request and the event broadcast to subscribers, and
alignment rounds it to 48 bytes, which puts its packet exactly on the
64-byte push floor — a test pins that, because a field added carelessly
would now overflow it. The interrupt report gives up eight bytes of inline
room to make space for the header; the two drivers that produce reports
send eight and four.

Suite 110/110.
This commit is contained in:
Daniel Samson
2026-08-01 07:20:37 +01:00
parent d2dfbcabf8
commit 2719b93530
27 changed files with 1058 additions and 685 deletions
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test/system/services/device-list/device-list.zig
+32 -27
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@@ -6,6 +6,7 @@
const std = @import("std");
const channel = @import("channel");
const envelope = @import("envelope");
const ipc = @import("ipc");
const time = @import("time");
const logging = @import("logging");
@@ -29,36 +30,41 @@ pub fn main() void {
};
// The snapshot — polled briefly, because at boot the bus drivers may still
// be scanning: an empty first answer usually just means "too early".
// be scanning: an empty first answer usually just means "too early". This is
// the envelope's reserved `enumerate` verb, so the request is nothing but a
// header and the answer is one `ChildEntry` per record in the reply's tail —
// how many arrived is the reply's own length, which is why no count header
// says it a second time.
const Entry = device_manager_protocol.ChildEntry;
const enumerate = envelope.Header{ .operation = envelope.operation_enumerate };
var reply: [device_manager_protocol.message_maximum]u8 = undefined;
var count: u32 = 0;
var length: usize = 0;
var count: usize = 0;
tries = 0;
while (tries < 20) : (tries += 1) {
const request = device_manager_protocol.Enumerate{};
length = ipc.call(h, std.mem.asBytes(&request), &reply) catch 0;
if (length >= @sizeOf(device_manager_protocol.EnumerateReply)) {
count = std.mem.bytesToValue(device_manager_protocol.EnumerateReply, reply[0..@sizeOf(device_manager_protocol.EnumerateReply)]).count;
if (count != 0) break;
const length = ipc.call(h, std.mem.asBytes(&enumerate), &reply) catch 0;
if (envelope.statusOf(reply[0..length])) |status| {
if (status.status == 0) {
const carried = @min(@as(usize, status.len), length - envelope.prefix_size);
count = carried / @sizeOf(Entry);
if (count != 0) break;
}
}
time.sleepMillis(100);
}
writeLine("device-list: {d} devices\n", .{count});
var offset: usize = @sizeOf(device_manager_protocol.EnumerateReply);
var index: u32 = 0;
while (index < count and offset + @sizeOf(device_manager_protocol.ChildEntry) <= length) : (index += 1) {
const entry = std.mem.bytesToValue(device_manager_protocol.ChildEntry, reply[offset..][0..@sizeOf(device_manager_protocol.ChildEntry)]);
for (0..count) |index| {
const entry = std.mem.bytesToValue(Entry, reply[envelope.prefix_size + index * @sizeOf(Entry) ..][0..@sizeOf(Entry)]);
writeLine("device-list: device {d} port {d} identity {d}\n", .{ entry.parent, entry.bus_address, entry.identity });
offset += @sizeOf(device_manager_protocol.ChildEntry);
}
// The subscription: our endpoint rides as the call's capability; events
// arrive as buffered messages carrying the same structs the bus sends.
// The subscription — the reserved `subscribe` verb: our endpoint rides as
// the call's capability, and events arrive as buffered packets carrying the
// same structs the bus drivers send, under the events' own numbering.
const endpoint = ipc.createIpcEndpoint() orelse {
_ = logging.write("device-list: no endpoint\n");
return;
};
const subscribe = device_manager_protocol.Subscribe{};
const subscribe = envelope.Header{ .operation = envelope.operation_subscribe };
_ = ipc.callCap(h, std.mem.asBytes(&subscribe), &reply, endpoint) catch {
_ = logging.write("device-list: subscribe failed\n");
return;
@@ -68,19 +74,18 @@ pub fn main() void {
var receive: [device_manager_protocol.message_maximum]u8 = undefined;
while (true) {
const got = ipc.replyWait(endpoint, &.{}, &receive, null);
if (!got.isMessage() or got.len < 1) continue;
switch (receive[0]) {
@intFromEnum(device_manager_protocol.Operation.child_added) => {
if (got.len < device_manager_protocol.child_added_size) continue;
const event = std.mem.bytesToValue(device_manager_protocol.ChildAdded, receive[0..device_manager_protocol.child_added_size]);
writeLine("device-list: added (device {d} port {d})\n", .{ event.parent, event.bus_address });
if (!got.isMessage()) continue;
const packet = receive[0..got.len];
const event = device_manager_protocol.Protocol.eventOf(packet) orelse continue;
switch (event) {
.child_added => {
const added = device_manager_protocol.Protocol.decodeEvent(.child_added, packet) orelse continue;
writeLine("device-list: added (device {d} port {d})\n", .{ added.parent, added.bus_address });
},
@intFromEnum(device_manager_protocol.Operation.child_removed) => {
if (got.len < device_manager_protocol.child_removed_size) continue;
const event = std.mem.bytesToValue(device_manager_protocol.ChildRemoved, receive[0..device_manager_protocol.child_removed_size]);
writeLine("device-list: removed (device {d} port {d})\n", .{ event.parent, event.bus_address });
.child_removed => {
const removed = device_manager_protocol.Protocol.decodeEvent(.child_removed, packet) orelse continue;
writeLine("device-list: removed (device {d} port {d})\n", .{ removed.parent, removed.bus_address });
},
else => {},
}
}
}