devicetree: generate extern's for devicetree struct devices

Generate a header (device_extern.h) that handles extern of possible
device structs that would come from devicetree.  This removes the need
for DEVICE_DT_DECLARE and DEVICE_DT_INST_DECLARE which we can remove.

Signed-off-by: Kumar Gala <[email protected]>

Author: galak

cmake/dts.cmake

@@ -21,6 +21,7 @@ set(ZEPHYR_DTS                  ${PROJECT_BINARY_DIR}/zephyr.dts)
 # and should not be made part of the documentation.
 set(EDT_PICKLE                  ${PROJECT_BINARY_DIR}/edt.pickle)
 set(DEVICETREE_UNFIXED_H        ${PROJECT_BINARY_DIR}/include/generated/devicetree_unfixed.h)
+set(DEVICE_EXTERN_H             ${PROJECT_BINARY_DIR}/include/generated/device_extern.h)
 set(DTS_POST_CPP                ${PROJECT_BINARY_DIR}/${BOARD}.dts.pre.tmp)
 
 set_ifndef(DTS_SOURCE ${BOARD_DIR}/${BOARD}.dts)
@@ -214,6 +215,7 @@ if(SUPPORTS_DTS)
   --dtc-flags '${EXTRA_DTC_FLAGS}'
   --bindings-dirs ${DTS_ROOT_BINDINGS}
   --header-out ${DEVICETREE_UNFIXED_H}
+  --device-header-out ${DEVICE_EXTERN_H}
   --dts-out ${ZEPHYR_DTS} # As a debugging aid
   --edt-pickle-out ${EDT_PICKLE}
   )
@@ -228,6 +230,7 @@ if(SUPPORTS_DTS)
   else()
     message(STATUS "Generated zephyr.dts: ${ZEPHYR_DTS}")
     message(STATUS "Generated devicetree_unfixed.h: ${DEVICETREE_UNFIXED_H}")
+    message(STATUS "Generated device_extern.h: ${DEVICE_EXTERN_H}")
   endif()
 
   # A file that used to be generated by 'dtc'. zephyr.dts is the new
@@ -237,4 +240,5 @@ if(SUPPORTS_DTS)
 
 else()
   file(WRITE ${DEVICETREE_UNFIXED_H} "/* WARNING. THIS FILE IS AUTO-GENERATED. DO NOT MODIFY! */")
+  file(WRITE ${DEVICE_EXTERN_H} "/* WARNING. THIS FILE IS AUTO-GENERATED. DO NOT MODIFY! */")
 endif(SUPPORTS_DTS)

include/device.h

@@ -767,6 +767,9 @@ static inline int device_pm_put_sync(const struct device *dev) { return -ENOTSUP
 }
 #endif
 
+/* device_extern is generated base on devicetree nodes */
+#include <device_extern.h>
+
 #include <syscalls/device.h>
 
 #endif /* ZEPHYR_INCLUDE_DEVICE_H_ */

scripts/dts/gen_defines.py

@@ -110,9 +110,35 @@ def main():
         write_chosen(edt)
         write_global_compat_info(edt)
 
+        write_device_extern_header(args.device_header_out, edt)
+
     if args.edt_pickle_out:
         write_pickled_edt(edt, args.edt_pickle_out)
 
+
+def write_device_extern_header(device_header_out, edt):
+    # Generate header that will extern devicetree struct device's
+
+    with open(device_header_out, "w", encoding="utf-8") as dev_header_file:
+        print("#ifndef DEVICE_EXTERN_GEN_H", file=dev_header_file)
+        print("#define DEVICE_EXTERN_GEN_H", file=dev_header_file)
+        print("", file=dev_header_file)
+        print("#ifdef __cplusplus", file=dev_header_file)
+        print('extern "C" {', file=dev_header_file)
+        print("#endif", file=dev_header_file)
+        print("", file=dev_header_file)
+
+        for node in sorted(edt.nodes, key=lambda node: node.dep_ordinal):
+            print(f"extern const struct device DEVICE_DT_NAME_GET(DT_{node.z_path_id});", file=dev_header_file)
+
+        print("", file=dev_header_file)
+        print("#ifdef __cplusplus", file=dev_header_file)
+        print("}", file=dev_header_file)
+        print("#endif", file=dev_header_file)
+        print("", file=dev_header_file)
+        print("#endif /* DEVICE_EXTERN_GEN_H */", file=dev_header_file)
+
+
 def setup_edtlib_logging():
     # The edtlib module emits logs using the standard 'logging' module.
     # Configure it so that warnings and above are printed to stderr,
@@ -159,6 +185,8 @@ def parse_args():
     parser.add_argument("--dts-out", required=True,
                         help="path to write merged DTS source code to (e.g. "
                              "as a debugging aid)")
+    parser.add_argument("--device-header-out", required=True,
+                        help="path to write device struct extern header to")
     parser.add_argument("--edt-pickle-out",
                         help="path to write pickled edtlib.EDT object to")