Daniel Samson
2719b93530
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.
92 lines
4.2 KiB
Zig
92 lines
4.2 KiB
Zig
//! device-list — the `ps` analog for the device tree (docs/device-manager.md
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//! M18.3): asks the device manager for the tree over IPC, prints it, then
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//! subscribes and prints every published add/remove event. The manager is the
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//! one answer to "what devices exist" for user space; nothing here touches a
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//! device_* system call.
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const std = @import("std");
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const channel = @import("channel");
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const envelope = @import("envelope");
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const ipc = @import("ipc");
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const time = @import("time");
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const logging = @import("logging");
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const device_manager_protocol = @import("device-manager-protocol");
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fn writeLine(comptime fmt: []const u8, arguments: anytype) void {
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var line: [96]u8 = undefined;
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_ = logging.write(std.fmt.bufPrint(&line, fmt, arguments) catch return);
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}
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pub fn main() void {
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var manager: ?ipc.Handle = null;
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var tries: u32 = 0;
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while (manager == null and tries < 200) : (tries += 1) {
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manager = channel.openEndpoint("device-manager");
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if (manager == null) time.sleepMillis(20);
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}
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const h = manager orelse {
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_ = logging.write("device-list: no device manager\n");
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return;
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};
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// The snapshot — polled briefly, because at boot the bus drivers may still
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// be scanning: an empty first answer usually just means "too early". This is
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// the envelope's reserved `enumerate` verb, so the request is nothing but a
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// header and the answer is one `ChildEntry` per record in the reply's tail —
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// how many arrived is the reply's own length, which is why no count header
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// says it a second time.
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const Entry = device_manager_protocol.ChildEntry;
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const enumerate = envelope.Header{ .operation = envelope.operation_enumerate };
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var reply: [device_manager_protocol.message_maximum]u8 = undefined;
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var count: usize = 0;
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tries = 0;
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while (tries < 20) : (tries += 1) {
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const length = ipc.call(h, std.mem.asBytes(&enumerate), &reply) catch 0;
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if (envelope.statusOf(reply[0..length])) |status| {
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if (status.status == 0) {
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const carried = @min(@as(usize, status.len), length - envelope.prefix_size);
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count = carried / @sizeOf(Entry);
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if (count != 0) break;
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}
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}
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time.sleepMillis(100);
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}
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writeLine("device-list: {d} devices\n", .{count});
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for (0..count) |index| {
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const entry = std.mem.bytesToValue(Entry, reply[envelope.prefix_size + index * @sizeOf(Entry) ..][0..@sizeOf(Entry)]);
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writeLine("device-list: device {d} port {d} identity {d}\n", .{ entry.parent, entry.bus_address, entry.identity });
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}
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// The subscription — the reserved `subscribe` verb: our endpoint rides as
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// the call's capability, and events arrive as buffered packets carrying the
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// same structs the bus drivers send, under the events' own numbering.
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const endpoint = ipc.createIpcEndpoint() orelse {
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_ = logging.write("device-list: no endpoint\n");
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return;
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};
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const subscribe = envelope.Header{ .operation = envelope.operation_subscribe };
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_ = ipc.callCap(h, std.mem.asBytes(&subscribe), &reply, endpoint) catch {
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_ = logging.write("device-list: subscribe failed\n");
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return;
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};
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_ = logging.write("device-list: subscribed\n");
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var receive: [device_manager_protocol.message_maximum]u8 = undefined;
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while (true) {
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const got = ipc.replyWait(endpoint, &.{}, &receive, null);
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if (!got.isMessage()) continue;
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const packet = receive[0..got.len];
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const event = device_manager_protocol.Protocol.eventOf(packet) orelse continue;
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switch (event) {
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.child_added => {
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const added = device_manager_protocol.Protocol.decodeEvent(.child_added, packet) orelse continue;
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writeLine("device-list: added (device {d} port {d})\n", .{ added.parent, added.bus_address });
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},
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.child_removed => {
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const removed = device_manager_protocol.Protocol.decodeEvent(.child_removed, packet) orelse continue;
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writeLine("device-list: removed (device {d} port {d})\n", .{ removed.parent, removed.bus_address });
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},
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}
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}
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}
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