rust: start supporting several bindgen versions

With both the workaround for `bindgen` 0.69.0 and the warning about
0.66.0 and 0.66.1 in place, start supporting several `bindgen` versions,
like it was done for the Rust compiler in a previous patch.

All other versions, including the latest 0.69.4, build without errors.

The `bindgen` project, like Rust, has also agreed to have the kernel
in their CI [1] -- thanks! This should help both projects: `bindgen`
will be able to detect early issues like those mentioned above, and the
kernel will be very likely build with new releases (at least for the
basic configuration being tested).

Link: rust-lang/rust-bindgen#2851 [1]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Documentation/rust/quick-start.rst

@@ -100,9 +100,10 @@ bindgen
 *******
 
 The bindings to the C side of the kernel are generated at build time using
-the ``bindgen`` tool. A particular version is required.
+the ``bindgen`` tool.
 
-Install it via (note that this will download and build the tool from source)::
+Install it, for instance, via (note that this will download and build the tool
+from source)::
 
 	cargo install --locked --version $(scripts/min-tool-version.sh bindgen) bindgen-cli
 

scripts/rust_is_available.sh

@@ -161,14 +161,6 @@ if [ "$rust_bindings_generator_cversion" -lt "$rust_bindings_generator_min_cvers
 	echo >&2 "***"
 	exit 1
 fi
-if [ "$rust_bindings_generator_cversion" -gt "$rust_bindings_generator_min_cversion" ]; then
-	echo >&2 "***"
-	echo >&2 "*** Rust bindings generator '$BINDGEN' is too new. This may or may not work."
-	echo >&2 "***   Your version:     $rust_bindings_generator_version"
-	echo >&2 "***   Expected version: $rust_bindings_generator_min_version"
-	echo >&2 "***"
-	warning=1
-fi
 if [ "$rust_bindings_generator_cversion" -eq 6600 ] || [ "$rust_bindings_generator_cversion" -eq 6601 ]; then
 	echo >&2 "***"
 	echo >&2 "*** Rust bindings generator '$BINDGEN' versions 0.66.0 and 0.66.1 may not"

scripts/rust_is_available_test.py

@@ -231,11 +231,6 @@ def test_bindgen_old_version(self):
         result = self.run_script(self.Expected.FAILURE, { "BINDGEN": bindgen })
         self.assertIn(f"Rust bindings generator '{bindgen}' is too old.", result.stderr)
 
-    def test_bindgen_new_version(self):
-        bindgen = self.generate_bindgen_version("bindgen 0.999.0")
-        result = self.run_script(self.Expected.SUCCESS_WITH_WARNINGS, { "BINDGEN": bindgen })
-        self.assertIn(f"Rust bindings generator '{bindgen}' is too new. This may or may not work.", result.stderr)
-
     def test_bindgen_bad_version_0_66_0_and_0_66_1(self):
         for version in ("0.66.0", "0.66.1"):
             with self.subTest(version=version):