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rtio: Add a context pool
Adds a context pool that can be used when a number of threads may be dynamically created to use with RTIO. While the pool has a small cost to it, the cost of verifying a statically declared kobject likely makes it worth avoiding dynamically allocating these with the typical kobject_alloc method. Instead this arena style pool of objects can be used where the kobject validation uses the gperf hash created at build time. Signed-off-by: Tom Burdick <thomas.burdick@intel.com>
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‎include/zephyr/rtio/pool.h

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/*
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* Copyright (c) 2025 Intel Corporation
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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/**
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* @file
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* @brief Real-Time IO pool API for maintaining a pool for RTIO contexts
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*/
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#ifndef ZEPHYR_INCLUDE_RTIO_POOL_H_
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#define ZEPHYR_INCLUDE_RTIO_POOL_H_
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#include "zephyr/kernel.h"
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#include <zephyr/sys/atomic.h>
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#include <zephyr/rtio/rtio.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/**
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* @brief RTIO Pool
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* @defgroup rtio_pool RTIO Pool API
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* @ingroup rtio
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* @{
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*/
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/**
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* @brief Pool of RTIO contexts to use with dynamically created threads
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*/
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struct rtio_pool {
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/** Size of the pool */
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size_t pool_size;
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/** Array containing contexts of the pool */
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struct rtio **contexts;
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/** Atomic bitmap to signal a member is used/unused */
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atomic_t *used;
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};
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/**
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* @brief Obtain an RTIO context from a pool
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*/
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__syscall struct rtio *rtio_pool_acquire(struct rtio_pool *pool);
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static inline struct rtio *z_impl_rtio_pool_acquire(struct rtio_pool *pool)
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{
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struct rtio *r = NULL;
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for (size_t i = 0; i < pool->pool_size; i++) {
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if (atomic_test_and_set_bit(pool->used, i) == 0) {
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r = pool->contexts[i];
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break;
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}
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}
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k_object_access_grant(r, k_current_get());
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return r;
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}
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/**
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* @brief Return an RTIO context to a pool
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*/
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__syscall void rtio_pool_release(struct rtio_pool *pool, struct rtio *r);
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static inline void z_impl_rtio_pool_release(struct rtio_pool *pool, struct rtio *r)
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{
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k_object_access_revoke(r, k_current_get());
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for (size_t i = 0; i < pool->pool_size; i++) {
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if (pool->contexts[i] == r) {
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atomic_clear_bit(pool->used, i);
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break;
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}
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}
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}
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/* clang-format off */
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/** @cond ignore */
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#define Z_RTIO_POOL_NAME_N(n, name) \
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name##_##n
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#define Z_RTIO_POOL_DEFINE_N(n, name, sq_sz, cq_sz) \
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RTIO_DEFINE(Z_RTIO_POOL_NAME_N(n, name), sq_sz, cq_sz)
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#define Z_RTIO_POOL_REF_N(n, name) \
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&Z_RTIO_POOL_NAME_N(n, name)
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/** @endcond */
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/**
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* @brief Statically define and initialize a pool of RTIO contexts
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*
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* @param name Name of the RTIO pool
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* @param pool_sz Number of RTIO contexts to allocate in the pool
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* @param sq_sz Size of the submission queue entry pool per context
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* @param cq_sz Size of the completion queue entry pool per context
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*/
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#define RTIO_POOL_DEFINE(name, pool_sz, sq_sz, cq_sz) \
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LISTIFY(pool_sz, Z_RTIO_POOL_DEFINE_N, (;), name, sq_sz, cq_sz); \
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static struct rtio * name##_contexts[] = { \
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LISTIFY(pool_sz, Z_RTIO_POOL_REF_N, (,), name) \
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}; \
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ATOMIC_DEFINE(name##_used, pool_sz); \
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STRUCT_SECTION_ITERABLE(rtio_pool, name) = { \
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.pool_size = pool_sz, \
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.contexts = name##_contexts, \
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.used = name##_used, \
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}
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/* clang-format on */
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/**
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* @}
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*/
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#ifdef __cplusplus
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}
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#endif
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#include <zephyr/syscalls/pool.h>
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#endif /* ZEPHYR_INCLUDE_RTIO_POOL_H_ */

‎scripts/build/gen_kobject_list.py

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@@ -114,6 +114,7 @@
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("ztest_test_rule", ("CONFIG_ZTEST", True, False)),
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("rtio", ("CONFIG_RTIO", False, False)),
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("rtio_iodev", ("CONFIG_RTIO", False, False)),
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("rtio_pool", ("CONFIG_RTIO", False, False)),
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("sensor_decoder_api", ("CONFIG_SENSOR_ASYNC_API", True, False))
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])
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‎subsys/rtio/CMakeLists.txt

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@@ -11,7 +11,7 @@ if(CONFIG_RTIO)
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zephyr_library_sources(rtio_executor.c)
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zephyr_library_sources(rtio_init.c)
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zephyr_library_sources(rtio_sched.c)
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zephyr_library_sources_ifdef(CONFIG_USERSPACE rtio_handlers.c)
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zephyr_library_sources_ifdef(CONFIG_USERSPACE rtio_syscalls.c)
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endif()
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zephyr_library_sources_ifdef(CONFIG_RTIO_WORKQ rtio_workq.c)

‎subsys/rtio/rtio_handlers.c renamed to ‎subsys/rtio/rtio_syscalls.c

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@@ -133,3 +133,22 @@ static inline int z_vrfy_rtio_submit(struct rtio *r, uint32_t wait_count)
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return z_impl_rtio_submit(r, wait_count);
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}
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#include <zephyr/syscalls/rtio_submit_mrsh.c>
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static inline struct rtio * z_vrfy_rtio_pool_acquire(struct rtio_pool *rpool)
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{
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K_OOPS(K_SYSCALL_OBJ(rpool, K_OBJ_RTIO_POOL));
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return z_impl_rtio_pool_acquire(rpool);
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}
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#include <zephyr/sysaclls/rtio_pool_acquire_mrsh.c>
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static inline void z_vrfy_rtio_pool_release(struct rtio_pool *rpool, struct rtio *r)
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{
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K_OOPS(K_SYSCALL_OBJ(rpool, K_OBJ_RTIO_POOL));
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K_OOPS(K_SYSCALL_OBJ(r, K_OBJ_RTIO));
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z_impl_rtio_pool_release(rpool, r);
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}
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#include <zephyr/sysaclls/rtio_pool_acquire_mrsh.c>

‎tests/subsys/rtio/rtio_api/CMakeLists.txt

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@@ -5,7 +5,7 @@ cmake_minimum_required(VERSION 3.20.0)
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find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
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project(rtio_api_test)
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target_sources(app PRIVATE src/test_rtio_api.c)
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target_sources(app PRIVATE src/test_rtio_api.c src/test_rtio_pool.c)
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target_include_directories(app PRIVATE
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${ZEPHYR_BASE}/include

‎tests/subsys/rtio/rtio_api/src/test_rtio_pool.c

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/*
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* Copyright (c) 2025 Intel Corporation.
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <errno.h>
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#include <zephyr/ztest.h>
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#include <zephyr/kernel.h>
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#include <zephyr/sys/atomic.h>
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#include <zephyr/sys/kobject.h>
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#include <zephyr/sys/libc-hooks.h>
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#include <zephyr/app_memory/mem_domain.h>
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#include <zephyr/sys/util_loops.h>
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#include <zephyr/sys/time_units.h>
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#include <zephyr/timing/timing.h>
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#include <zephyr/rtio/rtio.h>
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#include <zephyr/rtio/pool.h>
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RTIO_POOL_DEFINE(rpool, 2, 8, 8);
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ZTEST_USER(rtio_pool, test_rtio_pool_acquire_release)
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{
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struct rtio *r = rtio_pool_acquire(&rpool);
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zassert_not_null(r, "expected valid rtio context");
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struct rtio_sqe nop_sqe;
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struct rtio_cqe nop_cqe;
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rtio_sqe_prep_nop(&nop_sqe, NULL, NULL);
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rtio_sqe_copy_in(r, &nop_sqe, 1);
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rtio_submit(r, 1);
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rtio_cqe_copy_out(r, &nop_cqe, 1, K_FOREVER);
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rtio_pool_release(&rpool, r);
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}
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static void *rtio_pool_setup(void)
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{
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#ifdef CONFIG_USERSPACE
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k_mem_domain_init(&rtio_domain, 0, NULL);
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k_mem_domain_add_partition(&rtio_domain, &rtio_partition);
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#if Z_LIBC_PARTITION_EXISTS
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k_mem_domain_add_partition(&rtio_domain, &z_libc_partition);
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#endif /* Z_LIBC_PARTITION_EXISTS */
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#endif /* CONFIG_USERSPACE */
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return NULL;
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}
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static void rtio_pool_before(void *a)
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{
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ARG_UNUSED(a);
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#ifdef CONFIG_USERSPACE
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k_object_access_grant(&rpool, k_current_get());
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#endif /* CONFIG_USERSPACE */
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}
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ZTEST_SUITE(rtio_pool, NULL, rtio_pool_setup, rtio_pool_before, NULL, NULL);

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