Carry project memory in the repo, with tools/memory-sync.sh

Claude Code keeps per-project memory at <home>/.claude/projects/<key>/,
where <key> is the project's absolute path with every separator and the
drive colon turned into a dash. That makes it both rename-fragile and
machine-specific, and this project has hit each of those once:

  - D:\DEV\Schunix -> D:\DEV\SchOS changed the key, and 43 memories were
    invisible until moved across by hand.
  - Development happens from Windows and from Linux, and each looks in a
    different place for the same checkout.

Committing .claude/memory/ fixes both -- git carries it across renames
and between hosts -- and `import` puts it wherever the local machine
expects. .claude/settings.local.json stays ignored: those are per-machine
permissions.

The colon maps to a dash rather than being dropped. Deleting it gives
D-DEV-SchOS, which matches nothing and silently finds zero memories; that
was the first attempt. On Git Bash the key comes from `cygpath -w`,
because Claude Code is a Windows program and sees D:\DEV\SchOS, not
/d/DEV/SchOS.

.claude/memory/schunix-device-model.md

@@ -0,0 +1,92 @@
+---
+name: schunix-device-model
+description: "The bus-agnostic device model behind /proc/devices, and the settled decision on how Linux drivers may be used."
+metadata: 
+  node_type: memory
+  type: project
+  originSessionId: 9d8a2aef-bcf0-47a0-96c6-f706efab4a95
+  modified: 2026-08-08T18:05:13.551Z
+---
+
+Built 2026-08-08. `include/device.h` + `kernel/dev/device.c`, readable at
+`/proc/devices`. Written up in `docs/drivers.md`. Supersedes the two separate
+arrays in `kernel/drivers/registry.c` as the answer to "what is attached".
+
+**Bus is provenance, class is capability** — keep them separate. `bus` is
+`platform`/`pci`/`usb`; `class` is `display`/`input`/`storage`/`net`/`bus`. A USB
+disk and a SATA disk are both `storage`. `device_find_class()` is how a consumer
+asks for "the display" without naming a driver, which is what stops the next
+display driver requiring edits to every consumer.
+
+Where a driver claims a device, **the driver's opinion beats the descriptor's**:
+`struct usb_driver` gained a `devclass` field distinct from the USB interface
+class, because the descriptor says what the device claims to be and the driver
+knows what it made of it. A USB driver that forgets to set it lands in `other`.
+
+Registration is automatic in `pci_bind()` and `usb_bind_all()` so a driver
+cannot forget; platform devices are registered by hand in
+`platform_register_devices()` in registry.c, in one readable block, matching
+that file's existing "a list you can read beats a list assembled by side
+effects" reasoning.
+
+Flat list with a bus tag, **not a device tree** — nothing walks a hierarchy yet.
+No lock: everything is added during single-threaded boot. **USB hotplug would
+break both assumptions** and needs a spinlock plus a reader lock in procfs.
+
+## The display class
+
+`include/display.h` + ops in `kernel/dev/vga.c`, published on the device by
+`vga_pci_driver.ops`. `struct pci_driver` gained an `ops` field for this —
+**it has to live on the driver, not be set inside probe()**, because
+`pci_bind()` registers the device *after* probe returns.
+
+Ops: `mode`, `acquire`, `present(x,y,w,h)`, `wait_vblank`. The wrappers in
+device.c null-check every op so consumers are not each written around a
+maybe-absent vtable.
+
+- **Back buffer comes from `dma_alloc()`, which is the wrong pool** and is used
+  because it is the only *physically contiguous* allocator in the kernel —
+  kalloc hands out single pages. 1.9 MB of a 4 MB arena meant for device rings.
+  Allocated lazily on first `acquire()`, never at boot. The real fix travels
+  with the E820 work ([[schunix-smp-and-memory-bugs]]).
+- **vblank is the 1987 VGA port 0x3DA bit 3**, not VBE — VBE's protected-mode
+  interface for this is optional and usually absent. Two loops (wait for the
+  current retrace to *end*, then for the next to begin), or you return
+  immediately having just missed one. Both loops are bounded so hardware that
+  never reports retrace cannot hang a caller holding the console lock.
+
+`echo d > /proc/sysrq` runs `display_selftest()`; `tools/dispshot.ps1`
+photographs it to `build/dispshot.ppm` — it was derived from crashshot.ps1 and
+originally kept its output path, so the two silently overwrote each other and
+`crashqr.py` then failed on a capture that was not a crash screen. The pattern is designed to fail visibly: quadrants slant on a
+stride error, change colour on a bpp error, and the 1px inset frame clips on an
+off-by-one in the present rectangle. Verified 2026-08-08.
+
+The console still writes *directly* to the framebuffer; the two paths coexist
+deliberately. Routing text through the back buffer would mean presenting per
+character.
+
+## Linux drivers — settled 2026-08-08
+
+Nexoniarz's decision, and the reasoning is correct: **not shipped, ever**; the
+user installs one themselves through a device manager and Schunix loads it.
+
+- *Distribution* is what triggers the GPL. A user obtaining and loading a driver
+  on their own machine is their act, not ours.
+- Implementing a *loader* from published documentation is clean-room and fine —
+  it stays clean-room only if written from docs, not transcribed from Linux
+  source. See [[schunix-licensing]].
+
+Also worth keeping separate when this resumes: "loadable modules" (a stable ABI
+plus a linker/loader, on top of this model) and "drivers out of kernel"
+(user-space processes, DriverKit-style — needs IPC and mmap, both of which
+already exist). They get bundled together in conversation and are different
+projects.
+
+## Adding /proc files
+
+Three places, all needed: a `PROC_*` id and a case in `proc_gen_global()` in
+`kernel/dev/procfs.c`, and a row in the `globals[]` table in
+`kernel/fs/procfs.c`. Miss the third and the file exists but cannot be opened by
+name. `sb_pad()` exists there now for column layout — cprintf has no width
+specifier.