scripts: `make rust-analyzer` for out-of-tree modules

Adds support for out-of-tree rust modules to use the `rust-analyzer`
make target to generate the rust-project.json file.

The change involves adding an optional parameter `external_src` to the
`generate_rust_analyzer.py` which expects the path to the out-of-tree
module's source directory. When this parameter is passed, I have chosen
not to add the non-core modules (samples and drivers) into the result
since these are not expected to be used in third party modules. Related
changes are also made to the Makefile and rust/Makefile allowing the
`rust-analyzer` target to be used for out-of-tree modules as well.

Link: https://github.com/Rust-for-Linux/linux/pull/914
Link: https://github.com/Rust-for-Linux/rust-out-of-tree-module/pull/2
Signed-off-by: Vinay Varma <varmavinaym@gmail.com>
Link: https://lore.kernel.org/r/20230411091714.130525-1-varmavinaym@gmail.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

3 files changed, 28 insertions, 16 deletions

diff --git a/Makefile b/Makefile
index 6bbf9db6b414..64ec209b26f0 100644
--- a/Makefile
+++ b/Makefile
@@ -1859,11 +1859,6 @@ rustfmt:
 rustfmtcheck: rustfmt_flags = --check
 rustfmtcheck: rustfmt
 
-# IDE support targets
-PHONY += rust-analyzer
-rust-analyzer:
-	$(Q)$(MAKE) $(build)=rust $@
-
 # Misc
 # ---------------------------------------------------------------------------
 
@@ -1924,6 +1919,7 @@ help:
 	@echo  '  modules         - default target, build the module(s)'
 	@echo  '  modules_install - install the module'
 	@echo  '  clean           - remove generated files in module directory only'
+	@echo  '  rust-analyzer	  - generate rust-project.json rust-analyzer support file'
 	@echo  ''
 
 __external_modules_error:
@@ -2065,6 +2061,11 @@ quiet_cmd_tags = GEN     $@
 tags TAGS cscope gtags: FORCE
 	$(call cmd,tags)
 
+# IDE support targets
+PHONY += rust-analyzer
+rust-analyzer:
+	$(Q)$(MAKE) $(build)=rust $@
+
 # Script to generate missing namespace dependencies
 # ---------------------------------------------------------------------------
 
diff --git a/rust/Makefile b/rust/Makefile
index 4124bfa01798..1ffdff6c2a34 100644
--- a/rust/Makefile
+++ b/rust/Makefile
@@ -373,8 +373,10 @@ quiet_cmd_rustc_library = $(if $(skip_clippy),RUSTC,$(RUSTC_OR_CLIPPY_QUIET)) L
 	$(if $(rustc_objcopy),;$(OBJCOPY) $(rustc_objcopy) $@)
 
 rust-analyzer:
-	$(Q)$(srctree)/scripts/generate_rust_analyzer.py $(srctree) $(objtree) \
-		$(RUST_LIB_SRC) > $(objtree)/rust-project.json
+	$(Q)$(srctree)/scripts/generate_rust_analyzer.py \
+		$(abs_srctree) $(abs_objtree) \
+		$(RUST_LIB_SRC) $(KBUILD_EXTMOD) > \
+		$(if $(KBUILD_EXTMOD),$(extmod_prefix),$(objtree))/rust-project.json
 
 redirect-intrinsics = \
 	__eqsf2 __gesf2 __lesf2 __nesf2 __unordsf2 \
diff --git a/scripts/generate_rust_analyzer.py b/scripts/generate_rust_analyzer.py
index 946e250c1b2a..848fa1ad92ba 100755
--- a/scripts/generate_rust_analyzer.py
+++ b/scripts/generate_rust_analyzer.py
@@ -6,10 +6,11 @@
 import argparse
 import json
 import logging
+import os
 import pathlib
 import sys
 
-def generate_crates(srctree, objtree, sysroot_src):
+def generate_crates(srctree, objtree, sysroot_src, external_src):
     # Generate the configuration list.
     cfg = []
     with open(objtree / "include" / "generated" / "rustc_cfg") as fd:
@@ -65,7 +66,7 @@ def generate_crates(srctree, objtree, sysroot_src):
         [],
         is_proc_macro=True,
     )
-    crates[-1]["proc_macro_dylib_path"] = "rust/libmacros.so"
+    crates[-1]["proc_macro_dylib_path"] = f"{objtree}/rust/libmacros.so"
 
     append_crate(
         "build_error",
@@ -95,19 +96,26 @@ def generate_crates(srctree, objtree, sysroot_src):
         "exclude_dirs": [],
     }
 
+    def is_root_crate(build_file, target):
+        try:
+            return f"{target}.o" in open(build_file).read()
+        except FileNotFoundError:
+            return False
+
     # Then, the rest outside of `rust/`.
     #
     # We explicitly mention the top-level folders we want to cover.
-    for folder in ("samples", "drivers"):
-        for path in (srctree / folder).rglob("*.rs"):
+    extra_dirs = map(lambda dir: srctree / dir, ("samples", "drivers"))
+    if external_src is not None:
+        extra_dirs = [external_src]
+    for folder in extra_dirs:
+        for path in folder.rglob("*.rs"):
             logging.info("Checking %s", path)
             name = path.name.replace(".rs", "")
 
             # Skip those that are not crate roots.
-            try:
-                if f"{name}.o" not in open(path.parent / "Makefile").read():
-                    continue
-            except FileNotFoundError:
+            if not is_root_crate(path.parent / "Makefile", name) and \
+               not is_root_crate(path.parent / "Kbuild", name):
                 continue
 
             logging.info("Adding %s", name)
@@ -126,6 +134,7 @@ def main():
     parser.add_argument("srctree", type=pathlib.Path)
     parser.add_argument("objtree", type=pathlib.Path)
     parser.add_argument("sysroot_src", type=pathlib.Path)
+    parser.add_argument("exttree", type=pathlib.Path, nargs="?")
     args = parser.parse_args()
 
     logging.basicConfig(
@@ -134,7 +143,7 @@ def main():
     )
 
     rust_project = {
-        "crates": generate_crates(args.srctree, args.objtree, args.sysroot_src),
+        "crates": generate_crates(args.srctree, args.objtree, args.sysroot_src, args.exttree),
         "sysroot_src": str(args.sysroot_src),
     }