ldls: the plan for running someone else's drivers

docs/plan/ldls.md. SchOS cannot write a driver for every device that exists
and no project can, so the only route to the hardware support an established
system has is to run Linux's. hybrid.md built the mechanisms for this and said
so; vgpud proved them. This is what they were for.

Five rules, and everything else is an implementation of them:

  1. Nothing GPL ever enters an image we build. The driver is the user's,
     obtained by them, loaded on their machine.
  2. It runs in a process, never in the kernel. Legally a module linked into
     our kernel is the strongest derivative-work argument that exists, and
     practically this is foreign code that must not be able to take the
     machine. FreeBSD has shipped from this position for a decade.
  3. Facts, not expression. A symbol's signature and a struct's offsets are
     facts a compiled driver depends on; comments, macro bodies and inline
     bodies are expression and are never carried over. Provenance recorded per
     file. Flagged in the doc as wanting real legal advice before shipping.
  4. One kernel version at a time, pinned and named, because Linux says in
     writing that it has no stable in-kernel ABI.
  5. The unresolved-symbol list is the specification. Load a real module and
     let the loader say what is missing rather than guessing the surface.

Four pieces: an ELF relocatable loader (ours, clean, no licence question), the
KPI shim (the actual work), /dev/pci as the back end (built), and one new
kernel interface -- a netdev whose backend is a process, which is the exact
analogue of display_ops and is four vtable entries wide.

First target is 8139too rather than r8169, and the reason is decisive: QEMU
emulates rtl8139 and does not emulate r8169, so the obvious choice cannot be
tested at all. 8139too is also smaller, needs no firmware, and uses the thin
mii helpers instead of dragging in phylib. r8169 is what proves it was general,
afterwards and much more cheaply.

The "what it will not do" section carries the honest list, including the two
that are not yet answered: no EXPORT_SYMBOL_GPL story, and no IOMMU -- which
for foreign drivers is a materially worse problem than for our own, and is the
strongest argument for one this project has produced.

hybrid.md is closed and leaves the register; ldls.md takes the slot, which is
the freeze rule working rather than being bent.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VQ7Qx8E1q1M1bbCq8QLHS2

docs/licensing.md

@@ -63,6 +63,11 @@ SchOS does not.
 ever, no matter how convenient. This is why the USB stack was written from the
 specification rather than ported.
 
+**"Cannot be adopted" is not the same as "cannot be run."** A driver the *user*
+obtains and loads on their own machine is their act, not a distribution by us —
+see §4 and [plan/ldls.md](plan/ldls.md), which is the layer built on exactly
+that distinction and which ships no Linux code of any kind.
+
 ---
 
 ## 3. NetBSD in particular