posix: separate option groups into c library ext and system interfaces

Separate the POSIX implementation into two categories:

- Extensions to ISO C
- System Interfaces

The first category include standalone functions that generally do not
require OS support or depend on any other features within the POSIX
specification. The Option Groups that comprise this category include

- POSIX_C_LIB_EXT: e.g. strnlen(), fnmatch()
- POSIX_C_LANG_SUPPORT_R: e.g. gmtime_r(), strtok_r()

The second category includes the majority of other POSIX Option Groups
that do require OS support. The latter group may also be categorized
generally as being NATIVE_LIBC_INCOMPATIBLE, although that might
eventually become more granular.

Signed-off-by: Chris Friedt <cfriedt@tenstorrent.com>

Author: cfriedt

lib/posix/CMakeLists.txt

@@ -1,5 +1,7 @@
 # SPDX-License-Identifier: Apache-2.0
 
-add_subdirectory(options)
 add_subdirectory_ifdef(CONFIG_EVENTFD eventfd)
+add_subdirectory_ifdef(CONFIG_POSIX_C_LANG_SUPPORT_R c_lang_support_r)
+add_subdirectory_ifdef(CONFIG_POSIX_C_LIB_EXT c_lib_ext)
 add_subdirectory_ifdef(CONFIG_POSIX_SHELL shell)
+add_subdirectory_ifdef(CONFIG_POSIX_SYSTEM_INTERFACES options)

lib/posix/Kconfig

@@ -1,10 +1,42 @@
 # Copyright (c) 2024 Meta
+# Copyright (c) 2025 Tenstorrent AI ULC
 #
 # SPDX-License-Identifier: Apache-2.0
 
 menu "POSIX API Support"
 
+# POSIX Subprofile Definitions
+rsource "Kconfig.profile"
+
+# Toolchain hooks for external implementations
+rsource "Kconfig.toolchain"
+
+# POSIX C Library Extensions
+# This menu is for POSIX Option Groups that do not require OS support.
+menu "POSIX C Library Extensions"
+rsource "c_lang_support_r/Kconfig"
+rsource "c_lib_ext/Kconfig"
+endmenu
+
+# POSIX System Interfaces
+menuconfig POSIX_SYSTEM_INTERFACES
+    bool "POSIX System Interfaces"
+	depends on !NATIVE_APPLICATION
+	select NATIVE_LIBC_INCOMPATIBLE
+    help
+      Select 'y' here to support POSIX System Interfaces within Zephyr.
+
+      Options in this menu are organized by POSIX subprofiling Option Group.
+
+      For more information, see
+      https://pubs.opengroup.org/onlinepubs/9699919799/xrat/V4_subprofiles.html
+
+
+if POSIX_SYSTEM_INTERFACES
 rsource "options/Kconfig"
+endif
+
+# POSIX Shell utilities
 rsource "shell/Kconfig"
 
 endmenu

lib/posix/options/Kconfig.profile renamed to lib/posix/Kconfig.profile

@@ -3,9 +3,8 @@
 # SPDX-License-Identifier: Apache-2.0
 
 config POSIX_API
-	bool "POSIX APIs"
-	depends on !NATIVE_APPLICATION
-	select NATIVE_LIBC_INCOMPATIBLE
+	bool "POSIX API (legacy)"
+	select POSIX_SYSTEM_INTERFACES
 	select POSIX_BASE_DEFINITIONS # clock_gettime(), pthread_create(), sem_get(), etc
 	select POSIX_AEP_REALTIME_MINIMAL # CLOCK_MONOTONIC, pthread_attr_setstack(), etc
 	select POSIX_NETWORKING if NETWORKING # inet_ntoa(), socket(), etc
@@ -32,14 +31,13 @@ choice POSIX_AEP_CHOICE
 	  https://pubs.opengroup.org/onlinepubs/9699919799/xrat/V4_subprofiles.html
 
 config POSIX_AEP_CHOICE_NONE
-	bool "No pre-defined POSIX subprofile"
+	bool "No POSIX subprofile"
 	help
-	  No pre-defined POSIX profile is selected.
+	  No POSIX subprofile is selected.
 
 config POSIX_AEP_CHOICE_BASE
-	bool "Base definitions (system interfaces)"
-	depends on !NATIVE_APPLICATION
-	select NATIVE_LIBC_INCOMPATIBLE
+	bool "Minimal POSIX System Profile"
+	depends on POSIX_SYSTEM_INTERFACES
 	select POSIX_BASE_DEFINITIONS
 	help
 	  Only enable the base definitions required for all POSIX systems.
@@ -49,8 +47,7 @@ config POSIX_AEP_CHOICE_BASE
 
 config POSIX_AEP_CHOICE_PSE51
 	bool "Minimal Realtime System Profile (PSE51)"
-	depends on !NATIVE_APPLICATION
-	select NATIVE_LIBC_INCOMPATIBLE
+	depends on POSIX_SYSTEM_INTERFACES
 	select POSIX_BASE_DEFINITIONS
 	select POSIX_AEP_REALTIME_MINIMAL
 	help
@@ -63,8 +60,7 @@ config POSIX_AEP_CHOICE_PSE51
 
 config POSIX_AEP_CHOICE_PSE52
 	bool "Realtime Controller System Profile (PSE52)"
-	depends on !NATIVE_APPLICATION
-	select NATIVE_LIBC_INCOMPATIBLE
+	depends on POSIX_SYSTEM_INTERFACES
 	select POSIX_BASE_DEFINITIONS
 	select POSIX_AEP_REALTIME_MINIMAL
 	select POSIX_AEP_REALTIME_CONTROLLER
@@ -78,8 +74,7 @@ config POSIX_AEP_CHOICE_PSE52
 
 config POSIX_AEP_CHOICE_PSE53
 	bool "Dedicated Realtime System Profile (PSE53)"
-	depends on !NATIVE_APPLICATION
-	select NATIVE_LIBC_INCOMPATIBLE
+	depends on POSIX_SYSTEM_INTERFACES
 	select POSIX_BASE_DEFINITIONS
 	select POSIX_AEP_REALTIME_MINIMAL
 	select POSIX_AEP_REALTIME_CONTROLLER
@@ -96,7 +91,9 @@ config POSIX_AEP_CHOICE_PSE53
 
 endchoice # POSIX_AEP_CHOICE
 
-# Base Definitions (System Interfaces)
+if POSIX_SYSTEM_INTERFACES
+
+# Mandatory POSIX System Interfaces (base profile)
 config POSIX_BASE_DEFINITIONS
 	bool
 	select POSIX_ASYNCHRONOUS_IO
@@ -184,3 +181,5 @@ config POSIX_AEP_REALTIME_DEDICATED
 
 	  For more information, please see
 	  https://pubs.opengroup.org/onlinepubs/9699919799/xrat/V4_subprofiles.html
+
+endif # POSIX_SYSTEM_INTERFACE

lib/posix/options/Kconfig.toolchain renamed to lib/posix/Kconfig.toolchain

@@ -0,0 +1 @@
+# intentionally empty

lib/posix/c_lang_support_r/CMakeLists.txt

@@ -0,0 +1,17 @@
+# SPDX-License-Identifier: Apache-2.0
+
+zephyr_include_directories(getopt)
+
+if (CONFIG_TC_PROVIDES_POSIX_C_LIB_EXT)
+  return()
+endif()
+
+zephyr_library()
+zephyr_library_sources(
+  fnmatch.c
+  getentropy.c
+  getopt/getopt.c
+  getopt/getopt_common.c
+)
+
+zephyr_library_sources_ifdef(CONFIG_GETOPT_LONG getopt/getopt_long.c)

lib/posix/options/Kconfig.c_lang_r renamed to lib/posix/c_lang_support_r/Kconfig

@@ -26,7 +26,7 @@ endif()
 
 if(CONFIG_POSIX_API OR CONFIG_POSIX_THREADS OR CONFIG_POSIX_TIMERS OR
   CONFIG_POSIX_MESSAGE_PASSING OR CONFIG_POSIX_FILE_SYSTEM OR
-  CONFIG_POSIX_C_LIB_EXT OR CONFIG_POSIX_SINGLE_PROCESS)
+  CONFIG_POSIX_SINGLE_PROCESS)
   # This is a temporary workaround so that Newlib declares the appropriate
   # types for us. POSIX features to be formalized as part of #51211
   zephyr_compile_options($<$<COMPILE_LANGUAGE:C>:-D_POSIX_THREADS>)
@@ -43,15 +43,6 @@ if (NOT CONFIG_TC_PROVIDES_POSIX_BARRIERS)
   zephyr_library_sources_ifdef(CONFIG_POSIX_BARRIERS barrier.c)
 endif()
 
-if (NOT CONFIG_TC_PROVIDES_POSIX_C_LIB_EXT)
-  zephyr_library_sources_ifdef(CONFIG_POSIX_C_LIB_EXT
-    fnmatch.c
-    getentropy.c
-    getopt/getopt.c
-    getopt/getopt_common.c
-  )
-endif()
-
 if (NOT CONFIG_TC_PROVIDES_POSIX_DEVICE_IO)
   zephyr_library_sources_ifdef(CONFIG_POSIX_DEVICE_IO
     # perror should be moved to the common libc
@@ -156,13 +147,6 @@ if (NOT CONFIG_TC_PROVIDES_XSI_SYSTEM_LOGGING)
   zephyr_library_sources_ifdef(CONFIG_XSI_SYSTEM_LOGGING syslog.c)
 endif()
 
-zephyr_library_sources_ifdef(CONFIG_GETOPT_LONG
-  getopt/getopt_long.c
-)
-zephyr_include_directories_ifdef(CONFIG_POSIX_C_LIB_EXT
-  getopt/
-)
-
 zephyr_library_include_directories(
   ${ZEPHYR_BASE}/kernel/include
   ${ARCH_DIR}/${ARCH}/include

lib/posix/c_lib_ext/CMakeLists.txt

@@ -4,14 +4,8 @@
 #
 # SPDX-License-Identifier: Apache-2.0
 
-menu "POSIX Options"
-
-rsource "Kconfig.profile"
-
 rsource "Kconfig.aio"
 rsource "Kconfig.barrier"
-rsource "Kconfig.c_lang_r"
-rsource "Kconfig.c_lib_ext"
 rsource "Kconfig.device_io"
 rsource "Kconfig.fd_mgmt"
 rsource "Kconfig.file_system_r"
@@ -41,7 +35,3 @@ rsource "Kconfig.xsi_threads_ext"
 endmenu # "X/Open system interfaces"
 
 rsource "Kconfig.compat"
-
-rsource "Kconfig.toolchain"
-
-endmenu # "POSIX Options"