---
name: schunix-sockets-and-evdev
description: "Unix domain sockets and /dev/input evdev both work; the one lock rule, the names-not-in-the-VFS tradeoff, and where the syscall numbers went"
metadata: 
  node_type: memory
  type: project
  originSessionId: 9d8a2aef-bcf0-47a0-96c6-f706efab4a95
  modified: 2026-08-05T07:12:20.950Z
---

Unix domain sockets (`kernel/net/unix.c`, `include/socket.h`, `kernel/sys/sys_net.c`)
and raw input events (`kernel/dev/input.c`, `include/input.h`) are both done and
verified — `tools\bootcheck.ps1 -Sock` and `-Evdev`.

**One lock for the whole socket table, deliberately.** A pipe gets a lock per
pipe because every operation touches one object; a socket operation touches
two, and per-socket locks need an ordering rule every path obeys or they
deadlock. Worse, a reader testing `peer_closed` under its own lock while the
closer sets it under the peer's has no interlock and sleeps through its own
wakeup. Don't "optimise" this into per-socket locks.

**Socket names live in a table, not the filesystem.** `ls -l /tmp/schcom` will
not show an `s` and `unlink()` of a socket path returns ENOENT. Fixing it
properly means a new inode type through both filesystems, iget, dirlookup and
stat — a VFS change, not a socket change. Everything that matters works.

`connect()` deliberately does **not** wait for `accept()`. A queued connection
is already established on Unix; blocking would deadlock any server that
connects to itself.

The syscalls had real Linux numbers assigned (41/49/50/43/42 and friends).
They were `NO_LINUX` stubs before, which meant a musl program calling
`socket()` got "bad syscall" from the ABI translation and never reached the
stub at all — same trap as [[schunix-shm-and-mmap]]. `shutdown` is registered
as `sockshutdown` because Schunix already has a native `shutdown` that powers
the machine off.

**evdev:** `/dev/input/event0` (keyboard) and `event1` (mouse), major 7, Linux
`struct input_event` layout. Fed by the PS/2 keyboard, the PS/2 mouse and USB
HID. The console keeps its own path — both consumers see every key, so keys
pressed during a test also land on the shell's input line.

Two things that are not obvious:
- Below 0x54 a Linux keycode **is** the AT set-1 scancode, so the PS/2 path
  needs no table. USB HID does need one (`hid_keycode[]`), because HID numbers
  keys by position and the AT set numbers them by matrix wiring order.
- A full event ring drops the **oldest** event. Dropping the newest is the
  obvious choice and it is wrong: the event most likely lost is a key release,
  and a lost release leaves the key held down forever.

See also [[schunix-console-tty]], [[schunix-framebuffer-device]],
[[schunix-verify-by-driving-shell]].