Phase 2 (part 2): move src/idc to src/kernel/idc

AGENTS.md

@@ -30,7 +30,8 @@ memory-partition markers and Kconfig hierarchy are documented in
 moving code, follow it:
 
 * **Place code in the right tier.** OS/HAL/boot/inter-core → a kernel-only directory
-  (`arch/`, `drivers/`, `idc/`, `init/`, `platform/`, `probe/`, `logging/`, `trace/`); audio
+  (`kernel/`, which is built into the `sof_kernel` library, and the directories not yet
+  moved there: `arch/`, `drivers/`, `platform/`, `probe/`, `logging/`, `trace/`); audio
   application logic → `audio/`; reusable pure code → a shared-library directory (`lib/`,
   `math/`, `module/`) kept free of privileged operations. Each top-level directory's
   `README.md` states its tier in a "Runs in:" banner — keep it accurate.

src/Kconfig

@@ -17,7 +17,7 @@ rsource "samples/Kconfig"
 rsource "schedule/Kconfig"
 rsource "schedule/Kconfig.threads_prio"
 
-rsource "idc/Kconfig"
+rsource "kernel/Kconfig"
 
 rsource "ipc/Kconfig"
 

src/audio/README.md

@@ -15,4 +15,4 @@ modules in user context.
 
 When adding a component here, keep it inside the application tier: allocate through the module
 allocation syscalls (`mod_*`), mark any globals shared with the kernel using the partition
-markers, and never call kernel-only subsystems (`drivers/`, `platform/`, `idc/`) directly.
+markers, and never call kernel-only subsystems (`drivers/`, `platform/`, `kernel/idc/`) directly.

src/include/sof/userspace/README.md

@@ -74,14 +74,18 @@ its subdirectories span all tiers.
 
 | Tier | Meaning | Directories |
 |------|---------|-------------|
-| **Kernel-only** | OS integration, HAL, boot, inter-core. Never executes in a user thread. Must not be reached directly from user code — only via a syscall. | `arch/`, `drivers/`, `idc/`, `init/`, `platform/`, `probe/` *, `logging/` *, `trace/` * |
+| **Kernel-only** | OS integration, HAL, boot, inter-core. Never executes in a user thread. Must not be reached directly from user code — only via a syscall. | `kernel/` (`kernel/idc/`, `kernel/init/`), `arch/`, `drivers/`, `platform/`, `probe/` *, `logging/` *, `trace/` * |
 | **Boundary / bridge** | Owns the syscalls and the thread / memory-domain setup. Split internally: some translation units run kernel-side, some user-side (e.g. `handler-kernel.c` vs `handler-user.c`, `zephyr_ll.c` vs `zephyr_ll_user.c`). | `schedule/`, `ipc/`, `library_manager/` *, `debug/debug_stream/` *, and (in the Zephyr integration tree) `zephyr/syscall/` |
 | **Application** | Audio pipeline / component logic that runs in user threads under userspace configs. | `audio/` |
 | **Shared library** | Context-agnostic code linked into whichever context calls it. Must stay "user-safe": no privileged operations (no direct MMIO, no spinlocks held across syscalls, no raw kernel object access) so it is safe when pulled into a user build. | `math/`, `module/` |
 | **Mixed** | A directory whose files span more than one tier; see its own README for per-file classification. | `lib/` |
 
 Directories marked * do not yet have a "Runs in:" README banner.
 
+Kernel-only code is being moved under `src/kernel/`, which Zephyr builds into a library of its
+own, `sof_kernel`, instead of `modules_sof`. The other kernel-only directories in the table
+follow one at a time.
+
 Classification is grep-verifiable — see [Verifying the taxonomy](#verifying-the-taxonomy).
 
 > **`zephyr/syscall/` is the model to grow toward.** The Zephyr integration tree already

src/kernel/CMakeLists.txt

@@ -10,4 +10,5 @@ if(zephyr)
 	set(ZEPHYR_CURRENT_LIBRARY sof_kernel)
 endif()
 
+add_subdirectory(idc)
 add_subdirectory(init)

src/kernel/Kconfig

@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: BSD-3-Clause
+
+# Code that only runs in kernel mode, see scripts/kernel_user_partition.txt.
+
+rsource "idc/Kconfig"

src/idc/README.md → src/kernel/idc/README.md

@@ -1,9 +1,9 @@
-# Inter-Domain / Inter-Core Communication (`src/idc`)
+# Inter-Domain / Inter-Core Communication (`src/kernel/idc`)
 
 > **Runs in:** Kernel-only — cross-core messaging (`idc.c`, `zephyr_idc.c`) runs in supervisor
 > context. User-space audio code triggers cross-core work indirectly through higher-level
 > subsystems, not by calling IDC directly. See
-> [User/kernel split](../include/sof/userspace/README.md).
+> [User/kernel split](../../include/sof/userspace/README.md).
 
 This directory implements the mechanism cores use to signal and hand work to each other. It is
 part of the OS-integration layer, not the audio application.

zephyr/CMakeLists.txt

@@ -237,7 +237,6 @@ add_subdirectory(../src/math/  math_unused_install/)
 # remaining directories (in alphabetical order)
 add_subdirectory(../src/audio/ audio_unused_install/)
 add_subdirectory(../src/debug/ debug_unused_install/)
-add_subdirectory(../src/idc/ idc_unused_install/)
 add_subdirectory(../src/ipc/  ipc_unused_install/)
 add_subdirectory(../src/kernel/ kernel_unused_install/)
 add_subdirectory(../src/lib/ lib_unused_install/)