device: make device dependencies optional

Device dependencies are not always required, so make them optional via
CONFIG_DEVICE_DEPS. When enabled, the gen_device_deps script will run so
that dependencies are collected and part of the final image. Related
APIs will be also made available. Since device dependencies are used in
just a few places (power domains), disable the feature by default. When
not enabled, a second linking pass will not be required.

Signed-off-by: Gerard Marull-Paretas <gerard.marull@nordicsemi.no>

CMakeLists.txt

@@ -54,7 +54,7 @@ set(CMAKE_EXECUTABLE_SUFFIX .elf)
 # into the `zephyr_final` target.
 #
 # Multiple linking stages are required in the following cases:
-# - device handles structs must be generated (CONFIG_HAS_DTS=y)
+# - device dependencies structs must be generated (CONFIG_DEVICE_DEPS=y)
 # - ISR tables must be generated (CONFIG_GEN_ISR_TABLES=y)
 # - Kernel objects hash tables (CONFIG_USERSPACE=y)
 # - Application memory partitions (CONFIG_USERSPACE=y)
@@ -75,7 +75,7 @@ set(ZEPHYR_LINK_STAGE_EXECUTABLE zephyr_pre${ZEPHYR_CURRENT_LINKER_PASS})
 # existing variable to allow slowly cleanup of linking stage handling.
 # Three stage linking active: pre0 -> pre1 -> final, this will correspond to `pre1`
 # Two stage linking active:   pre0 -> final, this will correspond to `pre0`
-if(CONFIG_USERSPACE OR CONFIG_HAS_DTS)
+if(CONFIG_USERSPACE OR CONFIG_DEVICE_DEPS)
   set(ZEPHYR_PREBUILT_EXECUTABLE zephyr_pre1)
 else()
   set(ZEPHYR_PREBUILT_EXECUTABLE zephyr_pre0)
@@ -912,7 +912,7 @@ zephyr_get_include_directories_for_lang(C
   STRIP_PREFIX # Don't use a -I prefix
   )
 
-if(CONFIG_HAS_DTS)
+if(CONFIG_DEVICE_DEPS)
   if(CONFIG_DEVICE_DEPS_DYNAMIC)
     set(dynamic_deps --dynamic-deps)
   endif()
@@ -1177,7 +1177,7 @@ if(CONFIG_USERSPACE)
   )
 endif()
 
-if(CONFIG_USERSPACE OR CONFIG_HAS_DTS)
+if(CONFIG_USERSPACE OR CONFIG_DEVICE_DEPS)
   configure_linker_script(
     ${ZEPHYR_CURRENT_LINKER_CMD}
     "${LINKER_PASS_${ZEPHYR_CURRENT_LINKER_PASS}_DEFINE}"

cmake/linker_script/common/common-rom.cmake

@@ -185,9 +185,11 @@ zephyr_iterable_section(NAME tracing_backend KVMA RAM_REGION GROUP RODATA_REGION
 zephyr_linker_section(NAME zephyr_dbg_info KVMA RAM_REGION GROUP RODATA_REGION NOINPUT ${XIP_ALIGN_WITH_INPUT})
 zephyr_linker_section_configure(SECTION zephyr_dbg_info INPUT ".zephyr_dbg_info" KEEP)
 
-zephyr_linker_section(NAME device_deps KVMA RAM_REGION GROUP RODATA_REGION NOINPUT ${XIP_ALIGN_WITH_INPUT} ENDALIGN 16)
-zephyr_linker_section_configure(SECTION device_deps INPUT .__device_deps_pass1* KEEP SORT NAME PASS LINKER_DEVICE_DEPS_PASS1)
-zephyr_linker_section_configure(SECTION device_deps INPUT .__device_deps_pass2* KEEP SORT NAME PASS NOT LINKER_DEVICE_DEPS_PASS1)
+if (CONFIG_DEVICE_DEPS)
+  zephyr_linker_section(NAME device_deps KVMA RAM_REGION GROUP RODATA_REGION NOINPUT ${XIP_ALIGN_WITH_INPUT} ENDALIGN 16)
+  zephyr_linker_section_configure(SECTION device_deps INPUT .__device_deps_pass1* KEEP SORT NAME PASS LINKER_DEVICE_DEPS_PASS1)
+  zephyr_linker_section_configure(SECTION device_deps INPUT .__device_deps_pass2* KEEP SORT NAME PASS NOT LINKER_DEVICE_DEPS_PASS1)
+endif()
 
 zephyr_iterable_section(NAME _static_thread_data KVMA RAM_REGION GROUP RODATA_REGION SUBALIGN 4)
 

drivers/power_domain/Kconfig

@@ -18,11 +18,13 @@ config POWER_DOMAIN_GPIO
 	depends on DT_HAS_POWER_DOMAIN_GPIO_ENABLED
 	depends on GPIO
 	depends on TIMEOUT_64BIT
+	select DEVICE_DEPS
 
 config POWER_DOMAIN_INTEL_ADSP
 	bool "Use Intel ADSP power gating mechanisms"
 	default y
 	depends on DT_HAS_INTEL_ADSP_POWER_DOMAIN_ENABLED
+	select DEVICE_DEPS
 	help
 	  Include Intel ADSP power domain control mechanisms
 

include/zephyr/device.h

@@ -388,15 +388,17 @@ struct device {
 	struct device_state *state;
 	/** Address of the device instance private data */
 	void *data;
+#if defined(CONFIG_DEVICE_DEPS) || defined(__DOXYGEN__)
 	/**
 	 * Optional pointer to dependencies associated with the device.
 	 *
 	 * This encodes a sequence of sets of device handles that have some
 	 * relationship to this node. The individual sets are extracted with
-	 * dedicated API, such as device_required_handles_get().
+	 * dedicated API, such as device_required_handles_get(). Only available
+	 * if @kconfig{CONFIG_DEVICE_DEPS} is enabled.
 	 */
 	Z_DEVICE_DEPS_CONST device_handle_t *deps;
-
+#endif /* CONFIG_DEVICE_DEPS */
 #if defined(CONFIG_PM_DEVICE) || defined(__DOXYGEN__)
 	/**
 	 * Reference to the device PM resources (only available if
@@ -453,6 +455,8 @@ device_from_handle(device_handle_t dev_handle)
 	return dev;
 }
 
+#if defined(CONFIG_DEVICE_DEPS) || defined(__DOXYGEN__)
+
 /**
  * @brief Prototype for functions used when iterating over a set of devices.
  *
@@ -668,6 +672,8 @@ int device_supported_foreach(const struct device *dev,
 			     device_visitor_callback_t visitor_cb,
 			     void *context);
 
+#endif /* CONFIG_DEVICE_DEPS */
+
 /**
  * @brief Get a @ref device reference from its @ref device.name field.
  *
@@ -760,6 +766,8 @@ static inline bool z_impl_device_is_ready(const struct device *dev)
 	static Z_DECL_ALIGN(struct device_state) Z_DEVICE_STATE_NAME(dev_id)   \
 		__attribute__((__section__(".z_devstate")))
 
+#if defined(CONFIG_DEVICE_DEPS) || defined(__DOXYGEN__)
+
 /**
  * @brief Synthesize the name of the object that holds device ordinal and
  * dependency data.
@@ -838,6 +846,8 @@ static inline bool z_impl_device_is_ready(const struct device *dev)
 			    (DT_SUPPORTS_DEP_ORDS(node_id)), ()) /**/          \
 	}
 
+#endif /* CONFIG_DEVICE_DEPS */
+
 /**
  * @brief Maximum device name length.
  *
@@ -873,7 +883,7 @@ static inline bool z_impl_device_is_ready(const struct device *dev)
 		.api = (api_),                                                 \
 		.state = (state_),                                             \
 		.data = (data_),                                               \
-		.deps = (deps_),                                               \
+		IF_ENABLED(CONFIG_DEVICE_DEPS, (.deps = (deps_),)) /**/        \
 		IF_ENABLED(CONFIG_PM_DEVICE, (.pm = (pm_),)) /**/              \
 	}
 
@@ -951,7 +961,8 @@ static inline bool z_impl_device_is_ready(const struct device *dev)
 			level, prio, api, state, ...)                          \
 	Z_DEVICE_NAME_CHECK(name);                                             \
                                                                                \
-	Z_DEVICE_DEPS_DEFINE(node_id, dev_id, __VA_ARGS__);                    \
+	IF_ENABLED(CONFIG_DEVICE_DEPS,                                         \
+		   (Z_DEVICE_DEPS_DEFINE(node_id, dev_id, __VA_ARGS__);))      \
                                                                                \
 	Z_DEVICE_BASE_DEFINE(node_id, dev_id, name, pm, data, config, level,   \
 			     prio, api, state, Z_DEVICE_DEPS_NAME(dev_id));    \

kernel/Kconfig

@@ -969,8 +969,17 @@ endmenu
 
 menu "Device Options"
 
+config DEVICE_DEPS
+	bool "Store device dependencies"
+	help
+	  When enabled, device dependencies will be stored so that they can be
+	  queried at runtime. Device dependencies are typically inferred from
+	  devicetree. Enabling this option will increase ROM usage (or RAM if
+	  dynamic device dependencies are enabled).
+
 config DEVICE_DEPS_DYNAMIC
 	bool "Dynamic device dependencies"
+	depends on DEVICE_DEPS
 	help
 	  Option that makes it possible to manipulate device dependencies at
 	  runtime.

kernel/device.c

@@ -100,6 +100,8 @@ bool z_device_is_ready(const struct device *dev)
 	return dev->state->initialized && (dev->state->init_res == 0U);
 }
 
+#ifdef CONFIG_DEVICE_DEPS
+
 static int device_visitor(const device_handle_t *handles,
 			   size_t handle_count,
 			   device_visitor_callback_t visitor_cb,
@@ -138,3 +140,5 @@ int device_supported_foreach(const struct device *dev,
 
 	return device_visitor(handles, handle_count, visitor_cb, context);
 }
+
+#endif /* CONFIG_DEVICE_DEPS */

kernel/include/kernel_offsets.h

@@ -73,8 +73,10 @@ GEN_OFFSET_SYM(_thread_t, tls);
 GEN_ABSOLUTE_SYM(__z_interrupt_stack_SIZEOF, sizeof(z_interrupt_stacks[0]));
 
 /* member offsets in the device structure. Used in image post-processing */
+#ifdef CONFIG_DEVICE_DEPS
 GEN_ABSOLUTE_SYM(_DEVICE_STRUCT_HANDLES_OFFSET,
 		 offsetof(struct device, deps));
+#endif
 
 #ifdef CONFIG_PM_DEVICE
 GEN_ABSOLUTE_SYM(_DEVICE_STRUCT_PM_OFFSET,

subsys/pm/device.c

@@ -174,6 +174,7 @@ int pm_device_power_domain_add(const struct device *dev,
 	return power_domain_add_or_remove(dev, domain, true);
 }
 
+#ifdef CONFIG_DEVICE_DEPS
 struct pm_visitor_context {
 	pm_device_action_failed_cb_t failure_cb;
 	enum pm_device_action action;
@@ -205,6 +206,7 @@ void pm_device_children_action_run(const struct device *dev,
 
 	(void)device_supported_foreach(dev, pm_device_children_visitor, &visitor_context);
 }
+#endif
 
 int pm_device_state_get(const struct device *dev,
 			enum pm_device_state *state)

subsys/shell/modules/device_service.c

@@ -27,6 +27,8 @@ static const char *get_device_name(const struct device *dev,
 
 	return name;
 }
+
+#ifdef CONFIG_DEVICE_DEPS
 struct cmd_device_list_visitor_context {
 	const struct shell *sh;
 	char *buf;
@@ -43,6 +45,7 @@ static int cmd_device_list_visitor(const struct device *dev,
 
 	return 0;
 }
+#endif /* CONFIG_DEVICE_DEPS */
 
 static int cmd_device_list(const struct shell *sh,
 			   size_t argc, char **argv)
@@ -77,6 +80,7 @@ static int cmd_device_list(const struct shell *sh,
 		}
 
 		shell_fprintf(sh, SHELL_NORMAL, " (%s)\n", state);
+#ifdef CONFIG_DEVICE_DEPS
 		if (!k_is_user_context()) {
 			struct cmd_device_list_visitor_context ctx = {
 				.sh = sh,
@@ -86,6 +90,7 @@ static int cmd_device_list(const struct shell *sh,
 
 			(void)device_required_foreach(dev, cmd_device_list_visitor, &ctx);
 		}
+#endif /* CONFIG_DEVICE_DEPS */
 	}
 
 	return 0;

tests/lib/devicetree/devices/prj.conf

@@ -1,3 +1,4 @@
 CONFIG_ZTEST=y
 CONFIG_I2C=n
 CONFIG_ZTEST_NEW_API=y
+CONFIG_DEVICE_DEPS=y

tests/subsys/pm/power_domain/prj.conf

@@ -1,4 +1,5 @@
 CONFIG_ZTEST=y
+CONFIG_DEVICE_DEPS=y
 CONFIG_DEVICE_DEPS_DYNAMIC=y
 CONFIG_PM=y
 CONFIG_PM_DEVICE=y