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The site and several documents still described the system as it was before virtual terminals, the new schinit, the hybrid work and descriptor passing. docs/architecture/init.md described the wrong program. It documented a single schinit that parses manifests and supervises jobs, which has not been true since PID 1 was split: PID 1 forks a supervisor, spawns jobs on its behalf and reaps; the job table lives in /proc/schinit; a heartbeat runs both ways; and proc_reincarnate() re-execs PID 1 in place rather than panicking. Rewritten around what exists, keeping the reasoning that is still load-bearing -- the five failures of the sibling-init scheme, the escalation ladder, and the three bugs in the reincarnation path that each had to happen before they were obvious. docs/plan/init.md is deleted, which is the tree's own rule for finished work and had not been applied. Fourteen source comments referenced it by part number, so they are repointed at the architecture doc by section name rather than left dangling -- a deleted document nobody notices is worse than a stale one. docs/architecture/devices.md gained the section it has been missing since /dev/pci existed: what a driver needs from a kernel, why mmap is checked against the caller's claims, why DMA is a call and not a mapping, and why the write back after an interrupt is not optional. Also that a released device does not come back by itself, which is true and was nowhere. docs/architecture/networking.md gained a descriptor-passing section, and docs/architecture/README.md's stack diagram gained the two layers and the third seam it was missing. "Two seams hold the whole thing together" has not been true since /dev/pci. docs/plan/README.md said the hybrid work was deliberately last, on the argument that an interface with no consumer is wrong in ways nobody can see. The argument was right; the conclusion was not, and the document now says why it changed -- the alternative to a driver compatibility layer is writing a driver for every device that exists, and the original objection is answered rather than ignored because SchOS's own drivers are the consumers. The site: a Hybrid section with the eviction transcript, cards for virtual terminals, schinit and drivers outside the kernel, and the numbers remeasured rather than estimated -- 46,961 lines, 207 syscalls. The boot log in app.js is from a boot taken today, and the lines are trimmed to what the console can show without clipping, each still a verbatim prefix of real output. Two small rendering fixes found by looking at the pages rather than assuming: .console pre's min-height is now scoped to the hero, so a static transcript sizes to its content instead of reserving eight lines it does not have; and the docs reader's contents panel strips inline marks from headings, so a heading written `proc_reincarnate()` no longer carries its backticks into the sidebar. Every intra-doc link checked; none broken. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01VQ7Qx8E1q1M1bbCq8QLHS2
138 lines
6.3 KiB
Markdown
138 lines
6.3 KiB
Markdown
# SchOS documentation
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Four kinds of document, kept in four directories, because they answer four
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different questions and go stale at four different rates.
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| **[architecture/](architecture/)** | *What SchOS is* | Present tense. Describes what is built and working. |
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| **[plan/](plan/)** | *What SchOS will be* | Future tense. Everything here is unbuilt. |
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| **[guides/](guides/)** | *How to work on it* | Imperative. Build it, test it, add to it. |
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| **[history/](history/)** | *Why it is the way it is* | Past tense. Bugs whose cause is not visible from the fix. |
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Plus two that belong to no category and apply to everything:
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**[licensing.md](licensing.md)** — read it before copying anyone else's code in —
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and **[branding/](branding/)**, which holds the marks and the rules for using
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them.
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---
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## The rule that keeps this from rotting
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> **When something is finished, it moves from `plan/` to `architecture/` and is
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> rewritten as a description of the thing rather than a record of building it.**
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A completed item is not a ticked checkbox. A ticked checkbox says the work
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happened; it does not say what the work *produced*, and six months later the
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checkbox is the only thing left and it explains nothing.
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So finishing a piece of work has three steps, and the third is not optional:
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1. The code works and is tested.
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2. The plan entry is deleted.
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3. A description exists in `architecture/` written for somebody who was not
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there — what it does, what shape it has, what it costs, and what it still
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does not do.
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This is not bookkeeping. The tree has already proved it necessary: the network
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stack was finished, verified end to end, and for a month afterwards the only
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description of it anywhere was a checkbox in a roadmap, four levels of
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indentation deep, written in the past tense of somebody arguing for the work
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rather than explaining the result.
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**The "what it does not do" section is the one that pays.** Every description in
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`architecture/` ends with one. A document that only lists a subsystem's
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strengths is marketing, and the reader who most needs the document is the one
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about to trip over a limitation nobody wrote down.
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---
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## Start here
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**New to the tree** → [architecture/README.md](architecture/README.md), the
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system layer by layer, then [guides/layout.md](guides/layout.md) for where the
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files are.
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**Trying to build it** → [guides/building.md](guides/building.md).
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**Wondering what happens next** → [plan/1.0.md](plan/1.0.md), which is the finish line, then [plan/README.md](plan/README.md) for the order.
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**Something is broken and it feels familiar** → [history/](history/). There is a
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good chance it is in there.
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---
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## architecture/ — what SchOS is
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| [README](architecture/README.md) | The system, layer by layer. Read first. |
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| [boot.md](architecture/boot.md) | Firmware to the first userspace process. |
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| [kernel.md](architecture/kernel.md) | SchIFT: memory, processes, scheduling, traps, signals, SMP. |
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| [syscalls.md](architecture/syscalls.md) | The call table, and the Linux personality that lets real software run. |
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| [filesystem.md](architecture/filesystem.md) | The VFS, the buffer cache, procfs, mounts. |
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| [schfs.md](architecture/schfs.md) | SchFS: the copy-on-write root filesystem. |
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| [devices.md](architecture/devices.md) | The device model, driver binding, the class vtables. |
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| [usb.md](architecture/usb.md) | xHCI, the USB core, and the class drivers. |
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| [graphics.md](architecture/graphics.md) | Framebuffer, text rendering, console, and the crash screen. |
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| [terminals.md](architecture/terminals.md) | The six virtual terminals, and how one is switched to. |
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| [networking.md](architecture/networking.md) | Drivers, lwIP, sockets — Unix and INET. |
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| [init.md](architecture/init.md) | `schinit`, PID 1 as a role, and the job manifests. |
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## plan/ — what SchOS will be
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| [README](plan/README.md) | The three current decisions and the order they happen in. |
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| [1.0.md](plan/1.0.md) | **The finish line.** What 1.0 contains, and what is explicitly deferred past it. |
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| [foundations.md](plan/foundations.md) | The kernel work everything else is blocked on. |
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| [wayland.md](plan/wayland.md) | The GUI stack, and what gets deleted to make room. |
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| [hybrid.md](plan/hybrid.md) | Moving drivers out of the kernel. |
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| [schapi.md](plan/schapi.md) | The long-term API layering, and the compatibility promise. |
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| [roadmap.md](plan/roadmap.md) | Everything else still open. |
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## guides/ — how to work on it
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| [building.md](guides/building.md) | Prerequisites and the build, per host. |
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| [testing.md](guides/testing.md) | The harnesses, and what each one actually proves. |
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| [layout.md](guides/layout.md) | Repository map, and how to add a program or a port. |
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| [adding-a-driver.md](guides/adding-a-driver.md) | Writing one, binding it, publishing its class vtable. |
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## branding/ — the marks
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| [README](branding/README.md) | Shift the logo, Guru the icon, SchCotie the mascot: what each is for, the colour rule, and why a raster is committed next to its SVG. |
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## history/ — why it is the way it is
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| [README](history/README.md) | What belongs in here and what does not. |
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| [kernel.md](history/kernel.md) | Bugs whose cause was nowhere near their symptom. |
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| [schfs.md](history/schfs.md) | The filesystem's own, from the same period as its design. |
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| [moving-to-linux.md](history/moving-to-linux.md) | The Windows-to-Fedora move, kept for the parts that recur. |
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---
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## Writing one of these
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Four conventions, all of them observable in the existing files:
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**State the cost.** Every design choice gave something up. A document that does
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not say what is a document that will be argued with later by somebody who only
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sees the downside.
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**Prefer the measured number to the remembered one.** "500 of 3565 files carry
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the advertising clause" is worth more than "some do", and it was worth the
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minute it took to count.
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**Write down the bug that shaped it.** Half the non-obvious code in this tree is
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non-obvious because something failed once. If a design is strange, the strangeness
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is load-bearing and the reader deserves to know why before changing it.
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**No dates in headings.** A date in a heading turns a description into a
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changelog, and the description is the thing with a long life. Dates belong in
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`history/`, where they mean something.
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