//! /system/drivers/usb-xhci-bus — the xHCI (USB 3) host-controller bus driver.
//! The device manager spawns **one instance per controller** it discovers (a
//! machine can carry several), passing the controller's device-tree id as
//! argv[1]; this instance claims that device and no other, so multiple
//! instances never fight over hardware.
//!
//! M18.2 (this increment): after the hello, real hardware — map the xHC's
//! register window (the first memory BAR; resource 0 is the ECAM config
//! space), read the capability registers, and walk the root-hub ports: one
//! `child_added` report to the manager per connected port, carrying the port
//! number and the PORTSC speed class as identity. No transfer rings yet —
//! descriptors and USB class matching are the USB track; the connect bit and
//! speed come straight from PORTSC, which reflects hardware state whether or
//! not the controller is running.

const std = @import("std");
const runtime = @import("runtime");
const protocol = runtime.device_manager_protocol;
const device = runtime.device;

/// Format one whole log line and emit it in a single `debug_write`, so
/// concurrent instances (one per controller) can never interleave mid-line.
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);
}

var controller_id: u64 = protocol.no_device;

/// Claim the assigned controller, find its register window, and hello the
/// manager. Any failure returns false: the process exits cleanly, which the
/// manager reads as "meant to stop" — a missing assignment is not a crash loop.
fn initialise(endpoint: runtime.ipc.Handle) bool {
    _ = endpoint;
    if (!device.claim(controller_id)) {
        writeLine("usb-xhci-bus: unable to claim controller device {d}\n", .{controller_id});
        return false;
    }

    // Fetch our own descriptor back for the controller's resources.
    const buffer = runtime.allocator().alloc(device.DeviceDescriptor, 64) catch {
        _ = runtime.system.write("usb-xhci-bus: out of memory\n");
        return false;
    };
    const total = device.enumerate(buffer);
    const descriptor = for (buffer[0..@min(total, buffer.len)]) |d| {
        if (d.id == controller_id) break d;
    } else {
        writeLine("usb-xhci-bus: device {d} not in the device tree\n", .{controller_id});
        return false;
    };

    // The xHC's registers live behind the first memory BAR. Resource 0 is the
    // function's ECAM configuration space (M15), so the walk starts at 1.
    var register_index: u64 = 0;
    const register_window = for (descriptor.resources[1..@intCast(descriptor.resource_count)], 1..) |resource, index| {
        if (resource.kind == @intFromEnum(device.ResourceKind.memory)) {
            register_index = index;
            break resource;
        }
    } else {
        writeLine("usb-xhci-bus: controller device {d} has no register BAR\n", .{controller_id});
        return false;
    };
    writeLine("usb-xhci-bus: claimed controller device {d} (registers at 0x{x}, {d} bytes)\n", .{
        controller_id,
        register_window.start,
        register_window.len,
    });
    register_base = device.mmioMap(controller_id, register_index) orelse {
        _ = runtime.system.write("usb-xhci-bus: mmio_map failed\n");
        return false;
    };

    // The handshake: role, protocol version, assignment — inside the manager's
    // deadline (the lookup retries cover the manager still registering).
    var manager: ?runtime.ipc.Handle = null;
    var tries: u32 = 0;
    while (manager == null and tries < 100) : (tries += 1) {
        manager = runtime.ipc.lookup(.device_manager);
        if (manager == null) runtime.system.sleep(20);
    }
    const h = manager orelse {
        _ = runtime.system.write("usb-xhci-bus: no device manager to hello\n");
        return false;
    };
    const hello = protocol.Hello{ .role = @intFromEnum(protocol.Role.bus), .device_id = controller_id };
    var reply: [protocol.message_maximum]u8 = undefined;
    const n = runtime.ipc.call(h, std.mem.asBytes(&hello), &reply) catch {
        _ = runtime.system.write("usb-xhci-bus: hello call failed\n");
        return false;
    };
    if (n < protocol.reply_size or std.mem.bytesToValue(protocol.HelloReply, reply[0..protocol.reply_size]).status != 0) {
        _ = runtime.system.write("usb-xhci-bus: hello refused\n");
        return false;
    }
    _ = runtime.system.write("usb-xhci-bus: hello acknowledged\n");

    scanPorts(h);
    return true;
}

var register_base: usize = 0;

/// One 32-bit volatile register read at `offset` from the mapped window.
fn readRegister(offset: usize) u32 {
    const register: *volatile u32 = @ptrFromInt(register_base + offset);
    return register.*;
}

/// The root-hub port scan: read the capability registers for the port count
/// and the operational-register offset, then one PORTSC per port. The connect
/// bit (CCS) and the speed field reflect hardware state directly — no
/// controller reset or run needed to *see* the devices; driving them needs the
/// rings (the USB track).
fn scanPorts(manager: runtime.ipc.Handle) void {
    // Capability registers: CAPLENGTH is byte 0 of the first dword; HCSPARAMS1
    // carries MaxPorts in bits 31:24.
    const capability_length = readRegister(0) & 0xFF;
    const structural = readRegister(0x04);
    const maximum_ports: u32 = structural >> 24;
    writeLine("usb-xhci-bus: {d} root-hub ports\n", .{maximum_ports});

    // PORTSC registers: operational base + 0x400 + 0x10 per port (1-based).
    var port: u32 = 1;
    var connected: u32 = 0;
    while (port <= maximum_ports) : (port += 1) {
        const port_status = readRegister(capability_length + 0x400 + 0x10 * (port - 1));
        if (port_status & 1 == 0) continue; // CCS: nothing connected
        connected += 1;
        const speed = (port_status >> 10) & 0xF; // the PORTSC port-speed class
        writeLine("usb-xhci-bus: port {d} connected (speed class {d})\n", .{ port, speed });

        const report = protocol.ChildAdded{
            .parent = controller_id,
            .bus_address = port,
            .identity = speed,
        };
        var reply: [protocol.message_maximum]u8 = undefined;
        _ = runtime.ipc.call(manager, std.mem.asBytes(&report), &reply) catch {
            writeLine("usb-xhci-bus: child report for port {d} failed\n", .{port});
            continue;
        };
    }
    if (connected == 0) _ = runtime.system.write("usb-xhci-bus: no devices connected\n");
}

/// No bus protocol to serve yet — transfer requests arrive with the USB track.
fn onMessage(message: []const u8, reply: []u8, sender: u32, capability: ?runtime.ipc.Handle) usize {
    _ = message;
    _ = reply;
    _ = sender;
    _ = capability;
    return 0;
}

pub fn main(init: runtime.process.Init) void {
    const argument = init.arguments.get(1) orelse {
        _ = runtime.system.write("usb-xhci-bus: missing controller device id (argv[1])\n");
        return;
    };
    controller_id = std.fmt.parseInt(u64, argument, 10) catch {
        writeLine("usb-xhci-bus: malformed controller device id '{s}'\n", .{argument});
        return;
    };
    runtime.service.run(protocol.message_maximum, .{
        .init = initialise,
        .on_message = onMessage,
    });
}

pub const panic = runtime.panic;
comptime {
    _ = &runtime.start._start; // pull the runtime entry shim into the image
}