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library: five protocols speak the envelope

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The folded header stops being a rule in a document and becomes the layout
on the wire. Verbs number from sixteen, leaving describe, enumerate,
subscribe and unsubscribe reserved and answered the same way by every
provider — none of them writes a line to do it. What each protocol used to
carry in a field of its own now travels in the header: a vfs node and a
display layer are the packet's target, and a reply opens with a status the
envelope stamps rather than one each protocol spelled for itself.

Display gains the most. One forty-byte request had served eleven verbs, so
attach_scanout smuggled stride through x, refresh through y and format
through colour, and every coordinate crossed as a bitcast. Per-operation
structs end all three: the fields have their own names and their own signs,
and the tile payload grows to 224 bytes because the prefix shrank. Scanout
loses a message maximum of 64 it had no business declaring — it answers
calls, and the floor for a call is 256 — and virtio-gpu stops hard-coding
that number at its harness.

Two changes are semantic rather than notational. A directory now ends at an
entry with no name, because the fixed part of a reply always travels and a
zero-length reply no longer exists to mean anything. And input joins the
service harness, the last loop in the tree that answered no ping and heard
no terminate; its subscriber table, its pruning and its fan-out are the
same code, and a shutdown now asks it to stop instead of killing it.

A new conformance case reads the registry's own listing and asks every
protocol it finds for its name, its version and its verb count, then offers
a verb nobody defines and requires -ENOSYS — the envelope's promise,
checked against providers rather than against itself. What it cannot reach
in that boot it names on the serial line instead of passing quietly.

Suite 110/110.
This commit is contained in:
Daniel Samson
2026-08-01 06:15:25 +01:00
parent b004b9c3eb
commit d2dfbcabf8
40 changed files with 1882 additions and 1008 deletions
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system/drivers/virtio-gpu/virtio-gpu.zig
+52 -44
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@@ -25,11 +25,19 @@ const memory = @import("memory");
const logging = @import("logging");
const mmio = @import("mmio");
const pci = @import("pci");
const envelope = @import("envelope");
const display_protocol = @import("display-protocol");
const scanout_protocol = @import("scanout-protocol");
const vp = @import("virtio-pci.zig");
const vg = @import("virtio-gpu-protocol.zig");
/// The generated scanout dispatch. One scanout per driver instance, so the
/// handler context is empty and the mode stays in this file's globals.
const Serve = scanout_protocol.Protocol.Provider(void);
const Invocation = envelope.Invocation;
const Answer = envelope.Answer;
/// The DisplayFormat (device-abi) our B8G8R8X8 scanout resource presents: bgrx = 1. Handed to
/// the compositor in the announce so it packs colours in the surface's byte order.
const display_format_bgrx: u32 = 1;
@@ -482,60 +490,60 @@ fn announce() void {
std.log.info("no display service to announce to (scanout-only)", .{});
return;
};
var request = display_protocol.Request{
.operation = @intFromEnum(display_protocol.Operation.attach_scanout),
.x = max_width, // the shared surface's row stride in pixels (it is sized to the max mode)
.y = edid_refresh_hz, // the panel refresh from EDID (0 = unknown) — the frame-clock seed
var packet: [display_protocol.message_maximum]u8 = undefined;
const framed = display_protocol.Protocol.encodeRequest(.attach_scanout, 0, .{
.stride = max_width, // the shared surface's row stride in pixels (it is sized to the max mode)
.width = current_width,
.height = current_height,
.colour = display_format_bgrx,
};
var reply: [display_protocol.reply_size]u8 = undefined;
_ = ipc.callCap(display, std.mem.asBytes(&request), &reply, surface.handle) catch {
.format = display_format_bgrx,
.refresh_hz = edid_refresh_hz, // from EDID (0 = unknown) — the frame-clock seed
}, &.{}, &packet) orelse return;
var reply: [display_protocol.message_maximum]u8 = undefined;
_ = ipc.callCap(display, framed, &reply, surface.handle) catch {
std.log.info("announce to display failed", .{});
return;
};
std.log.info("announced scanout to display", .{});
}
/// A `scanout_protocol.Reply{status}` written into `reply`.
fn scanoutStatus(reply: []u8, ok: bool) usize {
const response = scanout_protocol.Reply{ .status = if (ok) 0 else -1 };
@memcpy(reply[0..scanout_protocol.reply_size], std.mem.asBytes(&response));
return scanout_protocol.reply_size;
// --- serving the scanout protocol -------------------------------------------
//
// The compositor drives present / mode queries here. The pixels are already in
// the shared surface, so a present is a transfer-to-host + fenced flush; a mode
// change just re-points the scanout rectangle (the surface is sized to the
// largest mode). One scanout, so `Header.target` is always 0.
/// The device did not take the frame, or the mode asked for is not one this
/// scanout offers.
const refused: isize = -envelope.ENOENT;
fn onPresent(_: void, _: Invocation(scanout_protocol.Present), _: Answer(void)) isize {
return if (presentFull()) 0 else refused;
}
/// The `.scanout` service: the compositor drives present / mode queries here. The pixels are
/// already in the shared surface, so a present is a transfer-to-host + fenced flush; a mode
/// change just re-points the scanout rectangle (the surface is sized to the largest mode).
fn onMessage(message: []const u8, reply: []u8, sender: u32, arrived: *ipc.Arrival) usize {
_ = sender;
_ = arrived; // nothing here takes a capability: the harness closes what arrives
if (message.len < scanout_protocol.request_size) return 0;
const request = std.mem.bytesToValue(scanout_protocol.Request, message[0..scanout_protocol.request_size]);
switch (request.operation) {
@intFromEnum(scanout_protocol.Operation.present) => return scanoutStatus(reply, presentFull()),
@intFromEnum(scanout_protocol.Operation.get_modes) => {
var response = scanout_protocol.ModesReply{ .status = 0, .count = offered_modes.len, .modes = undefined };
for (0..scanout_protocol.max_modes) |i| {
response.modes[i] = if (i < offered_modes.len)
.{ .width = offered_modes[i].width, .height = offered_modes[i].height }
else
.{ .width = 0, .height = 0 };
}
@memcpy(reply[0..scanout_protocol.modes_reply_size], std.mem.asBytes(&response));
return scanout_protocol.modes_reply_size;
},
@intFromEnum(scanout_protocol.Operation.set_mode) => {
const w = request.width;
const h = request.height;
if (w == 0 or h == 0 or w > max_width or h > max_height) return scanoutStatus(reply, false);
current_width = w;
current_height = h;
return scanoutStatus(reply, setScanoutRect());
},
else => return 0,
fn onGetModes(_: void, _: Invocation(void), answer: Answer(scanout_protocol.Modes)) isize {
var offered = scanout_protocol.Modes{ .count = offered_modes.len };
for (0..@min(offered_modes.len, scanout_protocol.max_modes)) |i| {
offered.modes[i] = .{ .width = offered_modes[i].width, .height = offered_modes[i].height };
}
answer.set(offered);
return 0;
}
fn onSetMode(_: void, invocation: Invocation(scanout_protocol.SetMode), _: Answer(void)) isize {
const w = invocation.request.width;
const h = invocation.request.height;
if (w == 0 or h == 0 or w > max_width or h > max_height) return refused;
current_width = w;
current_height = h;
return if (setScanoutRect()) 0 else refused;
}
const handlers = Serve.Handlers{ .present = onPresent, .get_modes = onGetModes, .set_mode = onSetMode };
fn onMessage(message: []const u8, reply: []u8, sender: u32, arrived: *ipc.Arrival) usize {
_ = arrived; // nothing here takes a capability: the harness closes what arrives
return Serve.dispatch({}, handlers, message, sender, null, reply);
}
pub fn main(init: process.Init) void {
@@ -547,7 +555,7 @@ pub fn main(init: process.Init) void {
std.log.info("malformed device id '{s}'", .{argument});
return;
};
service.run(256, .{
service.run(scanout_protocol.message_maximum, .{
.service = "scanout",
.init = initialise,
.on_message = onMessage,