llext: export DT devices to extensions

This change adds a new configuration option, LLEXT_EXPORT_DEVICES, which
enables exporting all devices defined in the device tree to llext
extensions. When enabled, all devices are made available to extensions
via the standard DT_ / DEVICE_* macros.

Signed-off-by: Luca Burelli <[email protected]>

Author: pillo79

include/zephyr/device.h

@@ -18,6 +18,10 @@
 #include <zephyr/sys/util.h>
 #include <zephyr/toolchain.h>
 
+#ifdef CONFIG_LLEXT
+#include <zephyr/llext/symbol.h>
+#endif
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -99,6 +103,11 @@ typedef int16_t device_handle_t;
  */
 #define Z_DEVICE_DT_DEV_ID(node_id) _CONCAT(dts_ord_, DT_DEP_ORD(node_id))
 
+#if defined(CONFIG_LLEXT_EXPORT_DEVICES)
+/* Export device identifiers using the builtin name */
+#define Z_DEVICE_EXPORT(node_id) EXPORT_SYMBOL(DEVICE_DT_NAME_GET(node_id))
+#endif
+
 /**
  * @brief Create a device object and set it up for boot time initialization.
  *
@@ -171,8 +180,9 @@ typedef int16_t device_handle_t;
  *
  * The device is declared with extern visibility, so a pointer to a global
  * device object can be obtained with `DEVICE_DT_GET(node_id)` from any source
- * file that includes `<zephyr/device.h>`. Before using the pointer, the
- * referenced object should be checked using device_is_ready().
+ * file that includes `<zephyr/device.h>` (even from extensions, when
+ * @kconfig{CONFIG_LLEXT_EXPORT_DEVICES} is enabled). Before using the
+ * pointer, the referenced object should be checked using device_is_ready().
  *
  * @param node_id The devicetree node identifier.
  * @param init_fn Pointer to the device's initialization function, which will be
@@ -197,7 +207,8 @@ typedef int16_t device_handle_t;
 			DEVICE_DT_NAME(node_id), init_fn, pm, data, config,    \
 			level, prio, api,                                      \
 			&Z_DEVICE_STATE_NAME(Z_DEVICE_DT_DEV_ID(node_id)),     \
-			__VA_ARGS__)
+			__VA_ARGS__)                                           \
+	IF_ENABLED(CONFIG_LLEXT_EXPORT_DEVICES, (; Z_DEVICE_EXPORT(node_id)))  \
 
 /**
  * @brief Like DEVICE_DT_DEFINE(), but uses an instance of a `DT_DRV_COMPAT`

subsys/llext/Kconfig

@@ -67,6 +67,12 @@ config LLEXT_STORAGE_WRITABLE
 	  Select if LLEXT storage is writable, i.e. if extensions are stored in
 	  RAM and can be modified in place
 
+config LLEXT_EXPORT_DEVICES
+	bool "Export all DT devices to llexts"
+	help
+	  When enabled, all Zephyr devices defined in the device tree are
+	  made available to llexts via the standard DT_ / DEVICE_* macros.
+
 config LLEXT_EXPORT_BUILTINS_BY_SLID
 	bool "Export built-in symbols to llexts via SLIDs"
 	help