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2a441af3c6
docs/plan/ldls.md L3a -- the class bridge, and the first of the three pieces
L3 turned out to be.
/dev/netdev is /dev/pci with the arrows reversed. That hands a device to a
process; this lets a process be one. The kernel side is netdev_ops and nothing
else -- transmit, receive, mac, link_up, the same four entries e1000
publishes -- so a process claims the device, supplies a MAC, and from then on
read() gives it frames the stack wants sent and write() hands it frames that
arrived.
cmd/netecho proves it and is deliberately not a driver: no hardware, none
claimed, every frame answered by the program itself. DHCP so the interface
gets an address at all, ARP so the stack can find it, ICMP so it can be
pinged. All built by hand from RFCs 826, 791, 792 and 2131.
# netecho &
netuser: ldls0 is a process now, 2:4c:44:4c:53:1
netecho: I am 10.9.0.1 and will offer 10.9.0.2
netecho: answered DHCP, offering an address
# cat /proc/netif
interface ldls0 driver netuser address 10.9.0.2 gateway 10.9.0.1
# ping 10.9.0.1 3
netecho: answered an ARP
netecho: answered a ping
3 packets transmitted, 3 received, 0% packet loss
The interface got its address by DHCP from a process and then answered ping
from one. lwIP never learns that the thing behind netdev_ops is not a driver,
which is the whole property the bridge exists to have.
It dies the way it should, too. kill the process and link_up() answers false
immediately, so the stack refuses to send -- "ping: sendto: -5" -- rather than
swallowing packets into a driver that is not there. Start another and the
*same* interface comes back, keeping its address. That came free:
netuser_release_all() sits beside pciuser_release_all() in exit() for exactly
the same reason, and the reason is that a process holding a device is one that
may crash.
One thing the kernel needed: netinit() starts DHCP on the devices that exist
when it runs, so an interface created later -- which is how an LDLS-hosted
driver arrives -- would have come up with no address and no way to get one.
net_attach_late() fixes that, and lives in kernel/net/net.c because that is
the only file allowed to include lwIP's headers.
Recorded as not done, because it is not: this proves the bridge, not a driver.
Nothing in that test loads a module. That is why it was done first -- if ping
had not worked here the bridge would be wrong, and now a failure with a real
driver can only be the driver's side. L3b is the SchOS-side host, L3c is the
fifteen symbols for real, and L3 is the two joined.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VQ7Qx8E1q1M1bbCq8QLHS2
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| .. | ||
| 1.0.md | ||
| debugger.md | ||
| foundations.md | ||
| hybrid.md | ||
| ldls.md | ||
| README.md | ||
| roadmap.md | ||
| schapi.md | ||
| wayland.md | ||
What happens next
Everything in this directory is unbuilt. When a piece of it is finished it leaves — deleted from here, rewritten as a description in ../architecture/. See the rule.
Read 1.0.md first.
It draws a finish line and puts most of the work below on the far side of it. Anything not named there is not being worked on, and the documents in this directory describe more than 1.0 contains.
It also holds the register of unfinished work, which is the one place anything half-built is listed. No new capability starts until that register is empty, and a row leaves it only by being finished or by being deleted from the tree.
The three current decisions
Taken together, because they turn out to need the same foundation.
| wayland.md | The GUI stack becomes Wayland. SchWM and SchDE are deleted — actually gone from the tree, not marked; Schcom survives and changes its wire format. |
| Built. All four mechanisms exist, the GPU driver runs outside the kernel, it survives being killed, and the display mode can be changed from a process. H4 (USB) was withdrawn rather than left open — USB is the bus peripherals arrive on, not a peripheral. | |
| Built. PID 1 is now a role the kernel refills; the description moved to ../architecture/init.md. |
And the one they all wait on:
| foundations.md | Descriptor passing, shared memory, sockets in the filesystem. The critical path. Item 1 is built — sendmsg/recvmsg with SCM_RIGHTS. |
And the one that says which parts of the above are actually being worked on:
| 1.0.md | The finish line. Four gates, and everything else explicitly deferred. |
And the one the hybrid mechanisms were built for:
| ldls.md | The Linux Driver Layer for SchOS. Someone else's drivers, in a process, reached through /dev/pci — because no project can write a driver for every device that exists. Not started. |
And one that is a tool rather than a capability:
| debugger.md | A debugger for this kernel — one that observes rather than halts, and answers in this kernel's own vocabulary. Built, except the network transport: symbols, a log that outlives the kernel, /dev/dbg, the whose ownership query and hardware watchpoints are all described in ../architecture/debugging.md. |
Two longer-horizon documents sit behind these: schapi.md, the API layering and the compatibility promise, and roadmap.md, which holds everything still open that is not one of the three above.
The order
Set by 1.0.md, which is the authority. In short:
0. Fix what is already wrong — first
Not a document of its own; it is Gate 0 of 1.0.md, assembled from the What it does not do sections in ../architecture/.
Before any new capability, and the reason is the one that put
netdev_selftest() before the TCP/IP stack: a compositor built on a kernel with
an unexplained hang and a socket layer that reports success for things it did not
do will fail in ways indistinguishable from its own bugs.
1. foundations.md — the critical path
Both the Wayland work and the hybrid work stop here. Descriptor passing and shared memory are the substrate for handing a buffer to a compositor and for handing a device to a driver process. Doing it once for both is the entire reason these are one plan rather than three.
2. init.md — before the desktop, not after — done
A compositor being brought up for the first time crashes constantly, and something that restarts it and says why is worth far more during that work than at the end of it. Built; see ../architecture/init.md.
3. hybrid.md — moved up, and the reason is worth recording
This document used to put the hybrid work after 1.0, deliberately last, on this argument:
designing a userspace driver interface with no driver consuming it produces an interface that is wrong in ways nobody can see
The argument was sound and the conclusion drawn from it was wrong. What forced the change was the driver situation: SchOS cannot write a driver for every device that exists, no project can, and the only route to the hardware support an established OS has is a compatibility layer with the foreign drivers kept outside the kernel. That layer is this plan's mechanisms. It is not optional and it is not late work.
The original argument still holds, and it is answered rather than ignored:
SchOS's own drivers are the consumers. vgpud is a real driver, with real
requirements, and building the interface against it is what keeps it a general
mechanism rather than a hole shaped like something foreign. The compositor is
still a demanding consumer — it is no longer the only one available.
Four mechanisms, all built. One eviction done, the second withdrawn with its reasons recorded, and the foreign driver host — ldls.md — is what they were for.
4. wayland.md — with the GPU driver either side of the seam
W1–W3 and a terminal. W4 and W5 are post-1.0. Item 1 of foundations.md —
descriptor passing — was the thing it could not start without, and it now
exists.
In one sentence
Fix what is broken, build the descriptor-passing and shared-memory substrate, make init survivable, move the drivers out through an interface SchOS's own drivers have to live with first — and put a terminal on the screen.
What this plan does not address
Stated here so it is not mistaken for covered:
- No IOMMU, so the hybrid work isolates against bugs and not against a hostile driver.
- No page cache, so
foundations.mddelivers amemfdand not a general answer to shared file mappings. The general answer is still owed. - No garbage collector for descriptors in flight, so an
AF_UNIXsocket passed over itself and never received leaks. Bounded at thirty-two sockets, and nothing on this plan does it. - No dynamic linking, so no Mesa, no accelerated clients, and no third party
shipping a
.sofor anything. - A new compatibility surface between PID 1 and PID 2, created by a plan whose own schapi.md §3 spends a section warning about those.
- The three open networking items —
getsockname, routing, and interrupt-driven receive — are untouched by any of this and still open. They are in roadmap.md.