Daniel Samson
47610e8ee2
The device manager is the ring-3 process that turns the device tree into a running system — the udev-analog. It is mechanism-vs-policy done right: the kernel enumerates the hardware and enforces the claim capability; this decides which driver serves which device, using no special privilege (the same device_enumerate any process could call). This first increment does the discovery + matching half: system/services/ device-manager enumerates /system/devices, matches each device to a driver by class (a small static policy table), and logs the decision — finding the HPET (a timer) and deciding `hpet` serves it. It does not spawn yet: spawning needs a `system_spawn` system call (the kernel spawns every initial-ramdisk binary in a loop today), which is the next increment. New `device-manager` test; suite 36/36 plus host tests.
59 lines
2.6 KiB
Zig
59 lines
2.6 KiB
Zig
//! /system/services/device-manager — the ring-3 process that turns the device
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//! tree into a running system. The kernel enumerates the hardware and enforces the
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//! claim capability (mechanism); this decides *which driver serves which device*
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//! and, eventually, spawns it (policy). Keeping that split in user space is the
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//! whole point of the microkernel: the manager is an ordinary, restartable process
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//! with no special privilege — it uses the same `device_*` system calls any process
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//! could ([drivers.md](../../../docs/drivers.md), [driver-model.md]).
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//!
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//! Increment 1 (this file): enumerate /system/devices and *match* each device to a
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//! driver, logging the decision. It does not spawn anything yet — spawning needs a
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//! `system_spawn` system call (the kernel spawns every initial-ramdisk binary in a
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//! loop today; see system/kernel/kernel.zig). Increment 2 adds that call and turns
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//! these decisions into actual spawns.
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const runtime = @import("runtime");
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const device = runtime.device;
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/// The driver that serves each device class — the policy table. In a fuller system
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/// this comes from the drivers describing what they bind (or a manifest under
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/// /system/drivers); for now it is a small static map, which is enough to prove the
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/// manager reads the tree and decides. `null` = no driver for this class yet.
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fn driverFor(class: u64) ?[]const u8 {
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if (class == @intFromEnum(device.DeviceClass.timer)) return "hpet"; // the HPET
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return null;
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}
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pub fn main() void {
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// Enumerate into a heap buffer (too big for the one-page user stack).
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const buffer = runtime.allocator().alloc(device.DeviceDescriptor, 64) catch {
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_ = runtime.system.write("device-manager: out of memory\n");
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return;
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};
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const total = device.enumerate(buffer);
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const count = @min(total, buffer.len);
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var matched: usize = 0;
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for (buffer[0..count]) |descriptor| {
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const driver_name = driverFor(descriptor.class) orelse continue;
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// Increment 2 will `system_spawn(driver_name)` here; for now, record the
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// decision so the policy is observable and testable.
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_ = runtime.system.write("device-manager: match ");
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_ = runtime.system.write(driver_name);
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_ = runtime.system.write(" -> would spawn it\n");
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matched += 1;
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}
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if (matched == 0) {
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_ = runtime.system.write("device-manager: no matchable devices\n");
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return;
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}
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_ = runtime.system.write("device-manager: ok\n");
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while (true) runtime.system.sleep(1000);
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}
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pub const panic = runtime.panic;
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comptime {
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_ = &runtime.start._start; // pull the runtime entry shim into the image
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}
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