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September 29, 2026 12:45
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🟡 Changes recommended
Several central architecture claims, file classifications, and syscall signatures do not match the current source and configuration.
Review effort: Balanced
Findings: 9
Open (9)
What changed in this PR
Documents SOF’s Zephyr user/kernel boundary and adds contributor guidance for preserving it.
Changes:
- Defines execution tiers, userspace configuration, memory partitions, and placement rules.
- Adds a centralized syscall-boundary index.
- Adds “Runs in” banners and agent guardrails across subsystems.
| File | Description |
|---|---|
AGENTS.md |
Adds user/kernel contribution rules. |
src/arch/README.md |
Classifies architecture support. |
src/audio/README.md |
Describes application-tier audio code. |
src/audio/module_adapter/README.md |
Classifies the module adapter boundary. |
src/drivers/README.md |
Documents driver privilege requirements. |
src/idc/README.md |
Classifies inter-core communication. |
src/include/sof/userspace/README.md |
Defines the overall userspace architecture. |
src/include/sof/userspace/syscalls.h |
Indexes SOF syscalls. |
src/init/README.md |
Classifies initialization code. |
src/ipc/README.md |
Documents IPC boundary behavior. |
src/ipc/ipc4/README.md |
Documents the IPC4 split. |
src/lib/README.md |
Classifies common-library code. |
src/math/README.md |
Documents user-safe math routines. |
src/module/README.md |
Classifies the module API. |
src/platform/README.md |
Classifies platform integration. |
src/schedule/README.md |
Documents scheduler execution contexts. |
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| * | ||
| * ## DMA | ||
| * Declared: sof/lib/sof_dma.h | ||
| * Kernel side: zephyr/syscall/sof_dma.c (z_vrfy_) / src/lib/dma.c (z_impl_) |
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| > **Runs in:** Kernel-only — boot and early bring-up run in supervisor context before any user | ||
| > thread exists; this code never executes in a user thread. See |
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| > **Runs in:** Shared library — **with a boundary exception.** Most of this directory | ||
| > (`lib.c`, `notifier.c`, `objpool.c`, `clk.c`, `agent.c`, `ams.c`, `cpu-clk-manager.c`) is | ||
| > context-agnostic helper code linked into whichever thread calls it and must stay user-safe. |
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| > memory-domain setup. It is split internally between kernel-side files (`zephyr_ll.c`, | ||
| > `zephyr_domain.c`, `zephyr_dp_schedule_thread.c`) and user-side files (`zephyr_ll_user.c`, | ||
| > `zephyr_ll_app.c`, `zephyr_dp_schedule_application.c`), and it hosts the |
lyakh
reviewed
Sep 30, 2026
SOF audio application logic now runs in Zephyr user-space on userspace configurations (e.g. Intel PTL with CONFIG_SOF_USERSPACE_LL), but the source layout gives no indication of which code runs in kernel vs user context or where the privilege boundary is crossed. Add a canonical reference under src/include/sof/userspace/ with README.md documenting the execution model, split between kernel and users and rules for placing new code. No functional change; documentation only. Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Make the user/kernel split evident at the point of use: each top-level src/ directory README now opens with a "Runs in:" banner declaring its tier (kernel-only / boundary / application / shared-library) and linking to the canonical reference in src/include/sof/userspace/README.md. Add banners to existing READMEs (schedule, ipc, ipc4, module_adapter, init, module) and add short new READMEs for directories that lacked one. lib/ is flagged as shared-library with a boundary exception, since dma.c and dai.c host syscall implementations. No functional change; documentation only. Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Add a "User/kernel boundary" subsection under Development Standards that points contributors to src/include/sof/userspace/README.md and states the requirements for new code: place it in the correct directory tier, cross the boundary only via a validated syscall, and mark any globals shared with user threads with a partition marker. Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
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PR 11247: test resultsRun date: 2026-10-07 06:43 UTC Tested commit: 961b21164118005d9a2f7b0683ec387e974d3fad
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Series of documentation patches to document the overall approach to user-space usage in SOF. This covers the main build options, adds a new central syscalls.h header for documentation and updates agent guardrails for new code.
Moving source files around was considered, but this is not yet done in this PR. As SOF supports multiple approaches: all-kernel (no MMU/MPU), mixed (single audio modules isolated) and app-code-all-in-user, for most source code files, the user/kernel split is not always the same. Starting with a documentation framework seems like the best approach to get started.